#ifndef DOXYGEN_SKIP
/* $Id: gdal_utilities.dox 18669 2010-01-27 02:07:32Z chaitanya $ */
#endif /* DOXYGEN_SKIP */

/*! 
\page gdal_utilities GDAL Utilities

The following utility programs are distributed with GDAL. 

<ul>
<li> \ref gdalinfo - report information about a file.
<li> \ref gdal_translate - Copy a raster file, with control of output format.
<li> \ref gdaladdo - Add overviews to a file.
<li> \ref gdalwarp - Warp an image into a new coordinate system.
<li> \ref gdaltindex - Build a MapServer raster tileindex.
<li> \ref gdalbuildvrt - Build a VRT from a list of datasets.
<li> \ref gdal_contour - Contours from DEM.
<li> \ref gdaldem - Tools to analyze and visualize DEMs.
<li> \ref rgb2pct - Convert a 24bit RGB image to 8bit paletted.
<li> \ref pct2rgb - Convert an 8bit paletted image to 24bit RGB.
<li> \ref gdal_merge - Build a quick mosaic from a set of images.
<li> \ref gdal2tiles - Create a TMS tile structure, KML and simple web viewer.
<li> \ref gdal_rasterize - Rasterize vectors into raster file.
<li> \ref gdaltransform - Transform coordinates.
<li> \ref nearblack - Convert nearly black/white borders to exact value.
<li> \ref gdal_retile - Retiles a set of tiles and/or build tiled pyramid levels.
<li> \ref gdal_grid - Create raster from the scattered data.
<li> \ref gdal_proximity - Compute a raster proximity map.
<li> \ref gdal_polygonize - Generate polygons from raster.
<li> \ref gdal_sieve - Raster Sieve filter.
<li> \ref gdal_fillnodata - Interpolate in nodata regions.
<li> \ref gdal-config - Get options required to build software using GDAL.
</ul>

\section gdal_utilities_creating Creating New Files

Access an existing file to read it is generally quite simple.  Just
indicate the name of the file or dataset on the commandline.  However, 
creating a file is more complicated.  It may be necessary to indicate the
the format to create, various creation options affecting how it will
be created and perhaps a coordinate system to be assigned.  Many of 
these options are handled similarly by different GDAL utilities, and are
introduced here. <p>

<dl>
<dt> <b>-of</b> <i>format</i></dt><dd> 
Select the format to create the new file as.  The formats are assigned short 
names such as GTiff (for GeoTIFF) or HFA (for Erdas Imagine).  The list of 
all format codes can be listed with the <b>--formats</b> switch.  Only
formats list as "(rw)" (read-write) can be written.<p>
Many utilities default
to creating GeoTIFF files if a format is not specified.  File extensions
are not used to guess output format, nor are extensions generally added
by GDAL if not indicated in the filename by the user. 
</dd>

<dt> <b>-co</b> <i>NAME=VALUE</i></dt><dd> 
Many formats have one or more optional creation options that can be used
to control particulars about the file created.  For instance, the GeoTIFF
driver supports creation options to control compression, and whether the file
should be tiled.<p>
The creation options available vary by format driver, and some simple 
formats have no creation options at all.  A list of options supported
for a format can be listed with the "--format <format>" commandline
option but the web page for the format is the definitive source of 
information on driver creation options.<p>
</dd>

<dt> <b>-a_srs</b> <i>SRS</i></dt><dd> 
Several utilities, (gdal_translate and gdalwarp) include the ability
to specify coordinate systems with commandline options like
<b>-a_srs</b> (assign SRS to output), <b>-s_srs</b> (source SRS) and
<b>-t_srs</b> (target SRS).<p>
These utilities allow the coordinate system (SRS = spatial reference system)
to be assigned in a variety of formats.<p>

<ul>
<li> <b>NAD27</b>/<b>NAD83</b>/<b>WGS84</b>/<b>WGS72</b>: 
These common geographic (lat/long) coordinate
systems can be used directly by these names. 

<li> <b>EPSG:</b><i>n</i>: Coordinate systems (projected or geographic) can
be selected based on their EPSG codes, for instance EPSG:27700 is the British
National Grid.  A list of EPSG coordinate systems can be found in the GDAL 
data files gcs.csv and pcs.csv. 

<li> <i>PROJ.4 Definitions</i>: A PROJ.4 definition string can be used
as a coordinate system.  For instance "+proj=utm +zone=11 +datum=WGS84".  
Take care to keep the proj.4 string together as a single argument to the
command (usually by double quoting). <p>

<li> <i>OpenGIS Well Known Text</i>: The Open GIS Consortium has defined
a textual format for describing coordinate systems as part of the Simple
Features specifications.  This format is the internal working format
for coordinate systems used in GDAL.  The name of a file containing a 
WKT coordinate system definition may be used a coordinate system argument,
or the entire coordinate system itself may be used as a commandline
option (though escaping all the quotes in WKT is quite challenging). <p>

<li> <i>ESRI Well Known Text</i>: ESRI uses a slight variation on OGC WKT
format in their ArcGIS product (ArcGIS .prj files), and these may be used
in a similar manner to WKT files, but the filename should be prefixed with
<b>ESRI::</b>.  For example <b>"ESRI::NAD 1927 StatePlane Wyoming West FIPS 4904.prj"</b>. <p>

<li> <i>Spatial References from URLs</i>: For example
http://spatialreference.org/ref/user/north-pacific-albers-conic-equal-area/.<p>

<li> <i>filename</i>: The name of a file containing WKT, PROJ.4 strings, or 
XML/GML coordinate system definitions can be provided. <p>

</ul>
</dd>
</dl>

\section gdal_utilities_switches General Command Line Switches
All GDAL command line utility programs support the following 
"general" options.<p>

<dl>
<dt> <b>--version</b></dt><dd> Report the version of GDAL and exit.</dd>

<dt> <b>--formats</b></dt><dd> List all raster formats supported by this
GDAL build (read-only and read-write) and exit. The format support is indicated
 as follows: 'ro' is read-only driver; 
'rw' is read or write (ie. supports CreateCopy);
'rw+' is read, write and update (ie. supports Create).  A 'v' is appended for formats supporting virtual IO (/vsimem, /vsigzip, /vsizip, etc).</dd>

<dt> <b>--format</b> <i>format</i></dt><dd>
List detailed information about a single format driver.  The <i>format</i> 
should be the short name reported in the <b>--formats</b> list, such as 
GTiff.</dd>

<dt> <b>--optfile</b> <i>file</i></dt><dd>
Read the named file and substitute the contents into the commandline
options list.  Lines beginning with # will be ignored.  Multi-word arguments
may be kept together with double quotes. 
</dd>

<dt> <b>--config</b> <i>key value</i></dt><dd>
Sets the named configuration keyword to the given value, as opposed to 
setting them as environment variables.  Some common configuration keywords
are GDAL_CACHEMAX (memory used internally for caching in megabytes)
and GDAL_DATA (path of the GDAL "data" directory).  Individual drivers may
be influenced by other configuration options. 
</dd>

<dt> <b>--debug</b> <i>value</i></dt><dd>
Control what debugging messages are emitted.  A value of <i>ON</i> will
enable all debug messages.  A value of <i>OFF</i> will disable all debug
messages.  Another value will select only debug messages containing that
string in the debug prefix code. 
</dd>

<dt> <b>--help-general</b></dt><dd>
Gives a brief usage message for the generic GDAL commandline options 
and exit.
</dd>

</dl>

\htmlonly
<p>
$Id: gdal_utilities.dox 18669 2010-01-27 02:07:32Z chaitanya $
</p>
\endhtmlonly
*/

*******************************************************************************
/*! \page gdalinfo gdalinfo

lists information about a raster dataset

\section synopsis SYNOPSIS

\verbatim
gdalinfo [--help-general] [-mm] [-stats] [-nogcp] [-nomd]
         [-noct] [-checksum] [-mdd domain]* datasetname
\endverbatim

\section description DESCRIPTION

The gdalinfo program lists various information about a GDAL supported
raster dataset. 
<dl>
<dt> <b>-mm</b></dt><dd> Force computation of the actual min/max values for each
band in the dataset.</dd>
<dt> <b>-stats</b></dt><dd> Read and display image statistics. Force computation if no statistics are stored in an image.</dd>
<dt> <b>-nogcp</b></dt><dd> Suppress ground control points list printing. It may be
useful for datasets with huge amount of GCPs, such as L1B AVHRR or HDF4 MODIS
which contain thousands of the ones.</dd>
<dt> <b>-nomd</b></dt><dd> Suppress metadata printing. Some datasets may contain a lot
of metadata strings.</dd>
<dt> <b>-noct</b></dt><dd> Suppress printing of color table.</dd>
<dt> <b>-checksum</b></dt><dd> Force computation of the checksum for each band in the dataset.</dd>
<dt> <b>-mdd domain</b></dt><dd> Report metadata for the specified domain</dd>
</dl>

The gdalinfo will report all of the following (if known):

<ul>
<li> The format driver used to access the file. 
<li> Raster size (in pixels and lines).
<li> The coordinate system for the file (in OGC WKT).
<li> The geotransform associated with the file (rotational coefficients are
currently not reported).  
<li> Corner coordinates in georeferenced, and if possible lat/long based on
the full geotransform (but not GCPs). 
<li> Ground control points.
<li> File wide (including subdatasets) metadata. 
<li> Band data types.
<li> Band color interpretations.
<li> Band block size.
<li> Band descriptions. 
<li> Band min/max values (internally known and possibly computed).
<li> Band checksum (if computation asked).
<li> Band NODATA value.
<li> Band overview resolutions available. 
<li> Band unit type (i.e.. "meters" or "feet" for elevation bands). 
<li> Band pseudo-color tables. 
</ul>

\section example EXAMPLE

\verbatim
gdalinfo ~/openev/utm.tif 
Driver: GTiff/GeoTIFF
Size is 512, 512
Coordinate System is:
PROJCS["NAD27 / UTM zone 11N",
    GEOGCS["NAD27",
        DATUM["North_American_Datum_1927",
            SPHEROID["Clarke 1866",6378206.4,294.978698213901]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",-117],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["metre",1]]
Origin = (440720.000000,3751320.000000)
Pixel Size = (60.000000,-60.000000)
Corner Coordinates:
Upper Left  (  440720.000, 3751320.000) (117d38'28.21"W, 33d54'8.47"N)
Lower Left  (  440720.000, 3720600.000) (117d38'20.79"W, 33d37'31.04"N)
Upper Right (  471440.000, 3751320.000) (117d18'32.07"W, 33d54'13.08"N)
Lower Right (  471440.000, 3720600.000) (117d18'28.50"W, 33d37'35.61"N)
Center      (  456080.000, 3735960.000) (117d28'27.39"W, 33d45'52.46"N)
Band 1 Block=512x16 Type=Byte, ColorInterp=Gray
\endverbatim

\if man
\section author AUTHORS
Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer <silke@intevation.de>
\endif
*/

*******************************************************************************
/*! \page gdal_translate gdal_translate

converts raster data between different formats

\section tsynopsis SYNOPSIS

\verbatim
gdal_translate [--help-general]
       [-ot {Byte/Int16/UInt16/UInt32/Int32/Float32/Float64/
             CInt16/CInt32/CFloat32/CFloat64}] [-strict]
       [-of format] [-b band] [-expand {gray|rgb|rgba}]
       [-outsize xsize[%] ysize[%]]
       [-unscale] [-scale [src_min src_max [dst_min dst_max]]]
       [-srcwin xoff yoff xsize ysize] [-projwin ulx uly lrx lry]
       [-a_srs srs_def] [-a_ullr ulx uly lrx lry] [-a_nodata value]
       [-gcp pixel line easting northing [elevation]]*
       [-mo "META-TAG=VALUE"]* [-q] [-sds]
       [-co "NAME=VALUE"]*
       src_dataset dst_dataset
\endverbatim

\section tdescription DESCRIPTION

The gdal_translate utility can be used to convert raster data between 
different formats, potentially performing some operations like subsettings, 
resampling, and rescaling pixels in the process.

<dl>
<dt> <b>-ot</b>: <i>type</i></dt><dd> For the output bands to be of the
indicated data type.</dd>
<dt> <b>-strict</b>:</dt><dd> Do'nt be forgiving of mismatches and lost data
when translating to the output format.</dd>
<dt> <b>-of</b> <i>format</i>:</dt><dd> Select the output format.  The default
is GeoTIFF (GTiff).  Use the short format name.</dd>
<dt> <b>-b</b> <i>band</i>:</dt><dd> Select an input band <i>band</i> for
output. Bands are numbered from 1 Multiple <b>-b</b> switches may be used
to select a set of input bands to write to the output file, or to reorder
bands.</dd>
<dt> <b>-expand</b> <i>gray|rgb|rgba</i>:</dt><dd> (From GDAL 1.6.0) To expose a dataset with 1 band
with a color table as a dataset with 3 (RGB) or 4 (RGBA) bands. Usefull for
output drivers such as JPEG, JPEG2000, MrSID, ECW that don't support color
indexed datasets. The 'gray' value (from GDAL 1.7.0) enables to expand a
dataset with a color table that only contains gray levels to a gray indexed
dataset.</dd>
<dt> <b>-outsize</b> <i>xsize[%] ysize[%]</i>:</dt><dd> Set the size of the output
file.  Outsize is in pixels and lines unless '%' is attached in which case it
is as a fraction of the input image size.</dd>
<dt> <b>-scale</b> <i>[src_min src_max [dst_min dst_max]]</i>:</dt><dd> Rescale the
input pixels values from the range <i>src_min</i> to <i>src_max</i> to
the range <i>dst_min</i> to <i>dst_max</i>.  If omitted the output range is
0 to 255.  If omitted the input range is automatically computed from the
source data.</dd>
<dt> <b>-unscale</b>:</dt><dd> Apply the scale/offset metadata for the bands
to convert scaled values to unscaled values.  It is also often necessary to 
reset the output datatype with the <b>-ot</b> switch.</dd>
<dt> <b>-srcwin</b> <i>xoff yoff xsize ysize</i>:</dt><dd> Selects a subwindow
from the source image for copying based on pixel/line location.  </dd>
<dt> <b>-projwin</b> <i>ulx uly lrx lry</i>:</dt><dd> Selects a subwindow from
the source image for copying (like <b>-srcwin</b>) but with the corners given
in georeferenced coordinates. </dd>
<dt> <b>-a_srs</b> <i>srs_def</i>:</dt><dd> Override the projection for the
output file.  The <i>srs_def</i> may be any of the usual GDAL/OGR forms,
complete WKT, PROJ.4, EPSG:n or a file containing the WKT. </dd>
<dt> <b>-a_ullr</b> <i>ulx uly lrx lry</i>:</dt><dd>
Assign/override the georeferenced bounds of the output file.  This assigns 
georeferenced bounds to the output file, ignoring what would have been derived 
from the source file.</dd>
<dt> <b>-a_nodata</b> <i>value</i>:</dt><dd>
Assign a specified nodata value to output bands.</dd>
<dt> <b>-mo</b> <i>"META-TAG=VALUE"</i>:</dt><dd> Passes a metadata key and
value to set on the output dataset if possible.</dd>
<dt> <b>-co</b> <i>"NAME=VALUE"</i>:</dt><dd> Passes a creation option to the
output format driver.  Multiple <b>-co</b> options may be listed.  See format 
specific documentation for legal creation options for each format.</dd>
<dt> <b>-gcp</b> <i>pixel line easting northing elevation</i>:</dt><dd>
Add the indicated ground control point to the output dataset.  This option 
may be provided multiple times to provide a set of GCPs. 
</dd>
<dt> <b>-q</b>:</dt><dd> Suppress progress monitor and other non-error
output.</dd>
<dt> <b>-sds</b>:</dt><dd> Copy all subdatasets of this file to individual 
output files.  Use with formats like HDF or OGDI that have subdatasets.</dd>
<dt> <i>src_dataset</i>:</dt><dd>The source dataset name. It can be either
file name, URL of data source or subdataset name for multi-dataset files.</dd>
<dt> <i>dst_dataset</i>:</dt><dd> The destination file name.</dd>
</dl>

\section texample EXAMPLE

\verbatim
gdal_translate -of GTiff -co "TILED=YES" utm.tif utm_tiled.tif
\endverbatim

\if man
\section tauthor AUTHORS
Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer <silke@intevation.de>
\endif
*/

*******************************************************************************
/*! \page gdaladdo gdaladdo

builds or rebuilds overview images

\section asynopsis SYNOPSIS

\verbatim
gdaladdo [-r {nearest,average,gauss,cubic,average_mp,average_magphase,mode}]
         [-ro] [-clean] [--help-general] filename levels
\endverbatim

\section adescription DESCRIPTION

The gdaladdo utility can be used to build or rebuild overview images for
most supported file formats with one over several downsampling algorithms. 

<dl>
<dt> <b>-r</b>
<i>{nearest (default),average,gauss,cubic,average_mp,average_magphase,mode}</i>:</dt><dd>
Select a resampling algorithm.</dd>
<dt> <b>-ro</b></dt>:<dd> (available from GDAL 1.6.0) open the dataset in read-only mode, in order to generate
external overview (for GeoTIFF especially). </dd>
<dt> <b>-clean</b></dt>:<dd> (available from GDAL 1.7.0) remove all overviews. </dd>
<dt> <i>filename</i>:</dt><dd> The file to build overviews for (or whose overviews must be removed). </dd>
<dt> <i>levels</i>:</dt><dd> A list of integral overview levels to build. Ignored with -clean option.</dd>
</dl>

<i>Mode</i> (available from GDAL 1.6.0) selects the value which appears most often of all the sampled points.
<i>average_mp</i> is unsuitable for use.
<i>Average_magphase</i> averages complex data in mag/phase space.  
<i>Nearest</i> and <i>average</i> are applicable to normal image data.  
<i>Nearest</i> applies a nearest neighbour (simple sampling) resampler, while
<i>average</i> computes the average of all non-NODATA contributing pixels.
<i>Cubic</i> resampling (available from GDAL 1.7.0) applies a 4x4 approximate cubic convolution kernel.
<i>Gauss</i> resampling (available from GDAL 1.6.0) applies a Gaussian kernel before computing the overview, 
which can lead to better results than simple averaging in e.g case of sharp edges
with high contrast or noisy patterns. The advised level values should be 2, 4, 8, ...
so that a 3x3 resampling Gaussian kernel is selected.

gdaladdo will honour properly NODATA_VALUES tuples (special dataset metadata) so
that only a given RGB triplet (in case of a RGB image) will be considered as the
nodata value and not each value of the triplet independantly per band. 

Selecting a level value like <i>2</i> causes an overview level that is 1/2
the resolution (in each dimension) of the base layer to be computed.  If
the file has existing overview levels at a level selected, those levels will
be recomputed and rewritten in place.

Some format drivers do not support overviews at all.  Many format drivers
store overviews in a secondary file with the extension .ovr that is actually
in TIFF format.  By default, the GeoTIFF driver stores overviews internally to the file 
operated on (if it is writable), unless the -ro flag is specified.

External overviews created in TIFF format may be compressed using the COMPRESS_OVERVIEW 
configuration option.  All compression methods, supported by the GeoTIFF 
driver, available here. (eg --config COMPRESS_OVERVIEW DEFLATE).
The photometric interpretation can be set with --config PHOTOMETRIC_OVERVIEW {RGB,YCBCR,...},
and the interleaving with --config INTERLEAVE_OVERVIEW {PIXEL|BAND}.

To produce the smallest possible JPEG-In-TIFF overviews, you should use :
\verbatim
--config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR --config INTERLEAVE_OVERVIEW PIXEL
\endverbatim

Starting with GDAL 1.7.0, external overviews can be created in the BigTIFF format by using
the BIGTIFF_OVERVIEW configuration option : --config BIGTIFF_OVERVIEW {IF_NEEDED|IF_SAFER|YES|NO}.
The default value is IF_NEEDED. The behaviour of this option is exactly the same as the BIGTIFF creation option
documented in the GeoTIFF driver documentation.
<ul>
    <li>YES forces BigTIFF.
    <li>NO forces classic TIFF.
    <li>IF_NEEDED will only create a BigTIFF if it is clearly needed (uncompressed, and overviews larger than 4GB).
    <li>IF_SAFER will create BigTIFF if the resulting file *might* exceed 4GB.
</ul>
<br>

Most drivers also support an alternate overview format using Erdas Imagine 
format.  To trigger this use the USE_RRD=YES configuration option.  This will 
place the overviews in an associated .aux file suitable for direct use with 
Imagine or ArcGIS as well as GDAL applications.  (eg --config USE_RRD YES)

\section aexample EXAMPLE

\htmlonly
Example:
\endhtmlonly

Create overviews, embedded in the supplied TIFF file:

\verbatim
gdaladdo -r average abc.tif 2 4 8 16
\endverbatim

Create an external compressed GeoTIFF overview file from the ERDAS .IMG file:

\verbatim
gdaladdo -ro --config COMPRESS_OVERVIEW DEFLATE erdas.img 2 4 8 16
\endverbatim

Create an external JPEG-compressed GeoTIFF overview file from a 3-band RGB dataset
(if the dataset is a writable GeoTIFF, you also need to add the -ro option to
force the generation of external overview):

\verbatim
gdaladdo --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR
         --config INTERLEAVE_OVERVIEW PIXEL rgb_dataset.ext 2 4 8 16
\endverbatim

Create an Erdas Imagine format overviews for the indicated JPEG file:

\verbatim
gdaladdo --config USE_RRD YES airphoto.jpg 3 9 27 81
\endverbatim

\if man
\section aauthor AUTHORS
Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer <silke@intevation.de>
\endif
*/

*******************************************************************************
/*! \page gdaltindex gdaltindex

builds a shapefile as a raster tileindex

\section isynopsis SYNOPSIS

\verbatim
gdaltindex [-tileindex field_name] [-write_absolute_path] [-skip_different_projection] index_file [gdal_file]*
\endverbatim

\section idescription DESCRIPTION

This program builds a shapefile with a record for each input raster file, 
an attribute containing the filename, and a polygon geometry outlining the
raster.  This output is suitable for use with <a href="http://mapserver.org/">MapServer</a> as a raster 
tileindex. 

<ul>
<li> The shapefile (index_file) will be created if it doesn't already exist, 
otherwise it will append to the existing file.
<li> The default tile index field is 'location'.
<li> Raster filenames will be put in the file exactly as they are specified
on the commandline unless the option -write_absolute_path is used.
<li> If -skip_different_projection is specified, only files with same projection ref
as files already inserted in the tileindex will be inserted.
<li> Simple rectangular polygons are generated in the same
coordinate system as the rasters.
</ul>

\section iexample EXAMPLE

\htmlonly
Example:
\endhtmlonly

\verbatim
gdaltindex doq_index.shp doq/*.tif
\endverbatim

\if man
\section wauthor AUTHOR
Frank Warmerdam <warmerdam@pobox.com>
\endif
*/


*******************************************************************************
/*! \page gdalbuildvrt gdalbuildvrt

Builds a VRT from a list of datasets. (compiled by default since GDAL 1.6.1)

\section gdalbuildvrt_synopsis SYNOPSIS

\verbatim
gdalbuildvrt [-tileindex field_name] [-resolution {highest|lowest|average|user}]
             [-tr xres yres] [-separate] [-allow_projection_difference] [-q]
             [-te xmin ymin xmax ymax] [-addalpha] [-hidenodata]
             [-srcnodata "value [value...]"] [-vrtnodata "value [value...]"]
             [-input_file_list my_liste.txt] output.vrt [gdalfile]*
\endverbatim

\section gdalbuildvrt_description DESCRIPTION

This program builds a VRT (Virtual Dataset) that is a mosaic of the list of
input gdal datasets. The list of input gdal datasets can be specified at the end
of the command line, or put in a text file (one filename per line) for very long lists,
or it can be a MapServer tileindex (see \ref gdaltindex utility). In the later case, all
entries in the tile index will be added to the VRT.

With -separate, each files goes into a separate <i>stacked</i> band in the VRT band. Otherwise,
the files are considered as tiles of a larger mosaic and the VRT file has as many bands as one
of the input files.

If one GDAL dataset is made of several subdatasets and has 0 raster bands,
all the subdatasets will be added to the VRT rather than the dataset itself.

gdalbuildvrt does some amount of checks to assure that all files that will be put
in the resulting VRT have similar characteristics : number of bands, projection, color
interpretation... If not, files that do not match the common characteristics will be skipped.
(This is only true in the default mode, and not when using the -separate option)

If there is some amount of spatial overlapping between files, the order may depend on the order they
are inserted in the VRT file, but this behaviour should not be relied on.

This utility is somehow equivalent to the gdal_vrtmerge.py utility and is build by default
in GDAL 1.6.1.

<dl>

<dt> <b>-tileindex</b>:</dt><dd> 
Use the specified value as the tile index field, instead of the default value with is 'location'. 
</dd>

<dt> <b>-resolution</b> {highest|lowest|average|user}:</dt><dd> 
In case the resolution of all input files is not the same, the -resolution flag
enables the user to control the way the output resolution is computed. 'average' is the default.
'highest' will pick the smallest values of pixel dimensions within the set of source rasters.
'lowest' will pick the largest values of pixel dimensions within the set of source rasters.
'average' will compute an average of pixel dimensions within the set of source rasters.
'user' is new in GDAL 1.7.0 and must be used in combination with the -tr option to specify the target resolution.
</dd>

<dt> <b>-tr</b> xres yres :</dt><dd>  (starting with GDAL 1.7.0)
set target resolution. The values must be expressed in georeferenced units.
Both must be positive values. Specifying those values is of curse incompatible with
highest|lowest|average values for -resolution option.
</dd>

<dt> <b>-te</b> xmin ymin xmax ymax :</dt><dd>  (starting with GDAL 1.7.0)
set georeferenced extents of VRT file. The values must be expressed in georeferenced units.
If not specified, the extent of the VRT is the minimum bounding box of the set of source rasters.
</dd>

<dt> <b>-addalpha</b>:</dt><dd> (starting with GDAL 1.7.0)
Adds an alpha mask band to the VRT when the source raster have none. Mainly useful for RGB sources (or grey-level sources).
The alpha band is filled on-the-fly with the value 0 in areas without any source raster, and with value
255 in areas with source raster. The effect is that a RGBA viewer will render
the areas without source rasters as transparent and areas with source rasters as opaque.
This option is not compatible with -separate.</dd>

<dt> <b>-hidenodata</b>:</dt><dd> (starting with GDAL 1.7.0)
Even if any band contains nodata value, giving this option makes the VRT band
not report the NoData. Useful when you want to control the background color of
the dataset. By using along with the -addalpha option, you can prepare a
dataset which doesn't report nodata value but is transparent in areas with no
data.</dd>

<dt> <b>-srcnodata</b> <em>value [value...]</em>:</dt><dd> (starting with GDAL 1.7.0)
Set nodata values for input bands (different values can be supplied for each band). If 
more than one value is supplied all values should be quoted to keep them 
together as a single operating system argument. If the option is not specified, the
instrinsic nodata settings on the source datasets will be used (if they exist). The value set by this option
is written in the NODATA element of each ComplexSource element. Use a value of
<tt>None</tt> to ignore intrinsic nodata settings on the source datasets.</dd>

<dt> <b>-vrtnodata</b> <em>value [value...]</em>:</dt><dd> (starting with GDAL 1.7.0)
Set nodata values at the VRT band level (different values can be supplied for each band).  If more
than one value is supplied all values should be quoted to keep them together
as a single operating system argument.  If the option is not specified,
instrinsic nodata settings on the first dataset will be used (if they exist). The value set by this option
is written in the NoDataValue element of each VRTRasterBand element. Use a value of
<tt>None</tt> to ignore intrinsic nodata settings on the source datasets.</dd>

<dt> <b>-separate</b>:</dt><dd> (starting with GDAL 1.7.0)
Place each input file into a separate <i>stacked</i> band. In that case, only the first
band of each dataset will be placed into a new band. Contrary to the default mode, it is not
required that all bands have the same datatype.
</dd>

<dt> <b>-allow_projection_difference</b>:</dt><dd> (starting with GDAL 1.7.0)
When this option is specified, the utility will accept to make a VRT even if the input datasets have
not the same projection. Note: this does not mean that they will be reprojected. Their projection will
just be ignored.
</dd>

<dt> <b>-input_file_list</b>:</dt><dd> 
To specify a text file with an input filename on each line
</dd>

<dt> <b>-q</b>:</dt><dd> (starting with GDAL 1.7.0)
To disable the progress bar on the console
</dd>

</dl>

\section gdalbuildvrt_example EXAMPLE

\htmlonly
Example:
\endhtmlonly

\verbatim
gdalbuildvrt doq_index.vrt doq/*.tif
gdalbuildvrt -input_file_list my_liste.txt doq_index.vrt
gdalbuildvrt -separate rgb.vrt red.tif green.tif blue.tif
\endverbatim

\if man
\section gdalbuildvrt_author AUTHOR
Even Rouault <even.rouault@mines-paris.org>
\endif
*/

*******************************************************************************
/*! \page gdal_contour gdal_contour

builds vector contour lines from a raster elevation model

\section gdal_contour_synopsis SYNOPSIS

\verbatim
Usage: gdal_contour [-b <band>] [-a <attribute_name>] [-3d] [-inodata]
                    [-snodata n] [-f <formatname>] [-i <interval>]
                    [-off <offset>] [-fl <level> <level>...]
                    [-nln <outlayername>]
                    <src_filename> <dst_filename> 
\endverbatim

\section gdal_contour_description DESCRIPTION

This program generates a vector contour file from the input raster elevation
model (DEM). 

Starting from version 1.7 the contour line-strings will be oriented
consistently. The high side will be on the right, i.e. a line string goes
clockwise around a top.

<dl>

<dt> <b>-b</b> <em>band</em>:</dt><dd> picks a particular band to get the DEM from.  Defaults to band 1.</dd>

<dt> <b>-a</b> <em>name</em>:</dt><dd>provides a name for the attribute in which to put the elevation. If not provided no elevation attribute is attached. </dd>
<dt> <b>-3d</b>:</dt> <dd>
      Force production of 3D vectors instead of 2D.  Includes elevation at
      every vertex.</dd>

<dt> <b>-inodata</b>:</dt> <dd> Ignore any nodata value implied in the dataset - treat all values as valid.</dd>

<dt> <b>-snodata</b> <em>value</em>:</dt><dd>
 Input pixel value to treat as "nodata". </dd>

<dt> <b>-f</b> <em>format</em>:</dt> <dd>
create output in a particular format, default is shapefiles.</dd>

<dt> <b>-i</b> <em>interval</em>:</dt><dd>
 elevation interval between contours.</dd>

<dt> <b>-off</b> <em>offset</em>:</dt><dd>
 Offset from zero relative to which to interpret intervals.</dd>

<dt> <b>-fl</b> <em>level</em>:</dt>
<dd> Name one or more "fixed levels" to extract.</dd>
<dt> <b>-nln</b> <em>outlayername</em>:</dt>
<dd> Provide a name for the output vector layer.  Defaults to "contour".</dd>
</dl>

\section gdal_contour_example EXAMPLE

This would create 10meter contours from the DEM data in dem.tif and produce
a shapefile in contour.shp/shx/dbf with the contour elevations in the "elev"
attribute.

\verbatim
gdal_contour -a elev dem.tif contour.shp -i 10.0
\endverbatim

\if man
\section gdal_contour_author AUTHORS
Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer <silke@intevation.de>
\endif
*/

*******************************************************************************
/*! \page gdal_rasterize gdal_rasterize

burns vector geometries into a raster

\section zsynopsis SYNOPSIS

\verbatim
Usage: gdal_rasterize [-b band] [-i] [-at]
       [-burn value] | [-a attribute_name] [-3d]
       [-l layername]* [-where expression] [-sql select_statement]
       <src_datasource> <dst_filename>
\endverbatim

\section zdescription DESCRIPTION

This program burns vector geometries (points, lines and polygons) into the 
raster band(s) of a raster image.  Vectors are read from OGR supported vector 
formats. 

Note that the vector data must in the same coordinate system as the 
raster data, on the fly reprojection is not provided.

<dl>
<dt> <b>-b</b> <em>band</em>: </dt><dd> 
The band(s) to burn values into.  Multiple -b arguments may be used to burn 
into a list of bands.  The default is to burn into band 1.</dd>

<dt> <b>-i</b>: </dt><dd>
Invert rasterization.  Burn the fixed burn value, or the burn value associated 
with the first feature into all parts of the image <em>not</em> inside the
provided a polygon.</dd>

<dt> <b>-at</b>: </dt><dd>
Enables the ALL_TOUCHED rasterization option so that all pixels touched
by lines or polygons will be updated not just those one the line render path,
or whose center point is within the polygon.  Defaults to disabled for normal
rendering rules.</dd>

<dt> <b>-burn</b> <em>value</em>: </dt><dd> 
A fixed value to burn into a band for all objects.  A list of -burn options 
can be supplied, one per band being written to.</dd>

<dt> <b>-a</b> <em>attribute_name</em>: </dt><dd> 
Identifies an attribute field on the features to be used for a burn in value.
The value will be burned into all output bands.</dd>

<dt> <b>-3d</b>: </dt><dd> 
Indicates that a burn value should be extracted from the "Z" values of the 
feature. These values are adjusted by the burn value given by "-burn value" or
"-a attribute_name" if provided. As of now, only points and lines are drawn in
3D.</dd>

<dt> <b>-l</b> <em>layername</em>: </dt><dd> 
Indicates the layer(s) from the datasource that will be used for input 
features.  May be specified multiple times, but at least one layer name or a -sql option must be specified.</dd>

<dt> <b>-where</b> <em>expression</em>: </dt><dd> 
An optional SQL WHERE style query expression to be applied to select features 
to burn in from the input layer(s). </dd>

<dt> <b>-sql</b> <em>select_statement</em>: </dt><dd> 
An SQL statement to be evaluated against the datasource to produce a
virtual layer of features to be burned in.</dd>

<dt> <em>src_datasource</em>: </dt><dd> 
Any OGR supported readable datasource.</dd>

<dt> <em>dst_filename</em>: </dt><dd> 
The GDAL supported output file.  Must support update mode access.  Currently 
gdal_rasterize cannot create new output files though that may be added eventually.</dd>

</dl>

\section zexample EXAMPLE

The following would burn all polygons from mask.shp into the RGB TIFF
file work.tif with the color red (RGB = 255,0,0).  

\verbatim
gdal_rasterize -b 1 -b 2 -b 3 -burn 255 -burn 0 -burn 0 -l mask mask.shp work.tif
\endverbatim

The following would burn all "class A" buildings into the output elevation
file, pulling the top elevation from the ROOF_H attribute.

\verbatim
gdal_rasterize -a ROOF_H -where 'class="A"' -l footprints footprints.shp city_dem.tif
\endverbatim

\if man
\section zauthor AUTHORS
Frank Warmerdam <warmerdam@pobox.com>
\endif
*/

*******************************************************************************
/*! \page rgb2pct rgb2pct.py

Convert a 24bit RGB image to 8bit paletted

\section rsynopsis SYNOPSIS

\verbatim
rgb2pct.py [-n colors | -pct palette_file] [-of format] source_file dest_file
\endverbatim

\section rdescription DESCRIPTION

This utility will compute an optimal pseudo-color table for a given RGB image
using a median cut algorithm on a downsampled RGB histogram.   Then it 
converts the image into a pseudo-colored image using the color table.
This conversion utilizes Floyd-Steinberg dithering (error diffusion) to 
maximize output image visual quality. 

<dl>
<dt> <b>-n</b> <i>colors</i>:</dt><dd> Select the number of colors in the generated
color table.  Defaults to 256.  Must be between 2 and 256. </dd>
<dt> <b>-pct</b> <i>palette_file</i>:</dt><dd> Extract the color table from
<i>palette_file</i> instead of computing it. Can be used to have a consistant
color table for multiple files. </dd>
<dt> <b>-of</b> <i>format</i>:</dt><dd> Format to generated (defaults to GeoTIFF).  Same
semantics as the <b>-of</b> flag for gdal_translate.  Only output formats
supporting pseudocolor tables should be used. </dd>
<dt> <i>source_file</i>:</dt><dd> The input RGB file. </dd>
<dt> <i>dest_file</i>:</dt><dd> The output pseudo-colored file that will be
created.</dd>
</dl>

NOTE: rgb2pct.py is a Python script, and will only work if GDAL was built
with Python support.  

\if man
\section iauthor AUTHOR
Frank Warmerdam <warmerdam@pobox.com>
\endif
*/

*******************************************************************************
/*! \page pct2rgb pct2rgb.py

Convert an 8bit paletted image to 24bit RGB

\section psynopsis SYNOPSIS

\htmlonly
Usage: 
\endhtmlonly

\verbatim
pct2rgb.py [-of format] [-b band] source_file dest_file
\endverbatim

\section pdescription DESCRIPTION

This utility will convert a pseudocolor band on the input file into an output
RGB file of the desired format. 

<dl>
<dt> <b>-of</b> <i>format</i>:</dt><dd> Format to generated (defaults to GeoTIFF).</dd>
<dt> <b>-b</b> <i>band</i>:</dt><dd> 
Band to convert to RGB, defaults to 1.</dd>
<dt> <i>source_file</i>:</dt><dd> The input file. </dd>
<dt> <i>dest_file</i>:</dt><dd> The output RGB file that will be
created.</dd>
</dl>

NOTE: pct2rgb.py is a Python script, and will only work if GDAL was built
with Python support.

The new '-expand rgb|rgba' option of gdal_translate obsoletes that utility.

\if man
\section pauthor AUTHORS
Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer <silke@intevation.de>
\endif
*/

*******************************************************************************
/*! \page gdaltransform gdaltransform
	
transforms coordinates 

\section fsynopsis SYNOPSIS

\verbatim
gdaltransform [--help-general]
    [-i] [-s_srs srs_def] [-t_srs srs_def] [-to "NAME=VALUE"]
    [-order n] [-tps] [-rpc] [-geoloc]
    [-gcp pixel line easting northing [elevation]]*
    [srcfile [dstfile]]
\endverbatim

\section fdescription DESCRIPTION

The gdaltransform utility reprojects a list of coordinates into any supported
projection,including  GCP-based transformations.

<dl>
<dt> <b>-s_srs</b> <em>srs def</em>:</dt><dd> source spatial reference set.
The coordinate systems that can be passed are anything supported by the
OGRSpatialReference.SetFromUserInput() call, which includes EPSG PCS and GCSes
(ie. EPSG:4296), PROJ.4 declarations (as above), or the name of a .prf file
containing well known text.</dd>
<dt> <b>-t_srs</b> <em>srs_def</em>:</dt><dd> target spatial reference set.
The coordinate systems that can be passed are anything supported by the
OGRSpatialReference.SetFromUserInput() call, which includes EPSG PCS and GCSes
(ie. EPSG:4296), PROJ.4 declarations (as above), or the name of a .prf file
containing well known text.</dd>
<dt> <b>-to</b> <em>NAME=VALUE</em>:</dt><dd> set a transformer option suitable
to pass to GDALCreateGenImgProjTransformer2(). </dd>
<dt> <b>-order</b> <em>n</em>:</dt><dd> order of polynomial used for warping
(1 to 3). The default is to select a polynomial order based on the number of
GCPs.</dd>
<dt> <b>-tps</b>:</dt><dd>Force use of thin plate spline transformer based on
available GCPs.</dd>
<dt> <b>-rpc</b>:</dt> <dd>Force use of RPCs.</dd>
<dt> <b>-geoloc</b>:</dt><dd>Force use of Geolocation Arrays.</dd>
<dt> <b>-i</b></dt><dd>Inverse transformation: from destination to source.</dd>
<dt> <b>-gcp</b><em>pixel line easting northing [elevation]</em>:</dt> <dd>Provide a GCP to be used for transformation (generally three or more are required)</dd>
<dt> <em>srcfile</em>:</dt><dd> File with source projection definition or GCP's. If
    not given, source projection is read from the command-line -s_srs or -gcp parameters </dd>
<dt> <em>dstfile</em>:</dt><dd> File with destination projection definition. </dd>
</dl>


Coordinates are read as pairs (or triples) of numbers per line from standard
input, transformed, and written out to standard output in the same way. All
transformations offered by gdalwarp are handled, including gcp-based ones.

Note that input and output must always be in decimal form.  There is currently
no support for DMS input or output.

If an input image file is provided, input is in pixel/line coordinates on that
image.  If an output file is provided, output is in pixel/line coordinates
on that image.  

\section fexample Reprojection Example

Simple reprojection from one projected coordinate system to another:

\verbatim
gdaltransform -s_srs EPSG:28992 -t_srs EPSG:31370
177502 311865
\endverbatim

Produces the following output in meters in the "Belge 1972 / Belgian Lambert 
72" projection:

\verbatim
244510.77404604 166154.532871342 -1046.79270555763
\endverbatim

\section gexample Image RPC Example

The following command requests an RPC based transformation using the RPC
model associated with the named file.  Because the -i (inverse) flag is
used, the transformation is from output georeferenced (WGS84) coordinates 
back to image coordinates. 

\verbatim
gdaltransform -i -rpc 06OCT20025052-P2AS-005553965230_01_P001.TIF
125.67206 39.85307 50                    
\endverbatim

Produces this output measured in pixels and lines on the image:
\verbatim
3499.49282422381 2910.83892848414 50
\endverbatim

\if man
\section fauthor AUTHORS
Frank Warmerdam <warmerdam@pobox.com>, Jan Hartmann <j.l.h.hartmann@uva.nl>
\endif
*/
*******************************************************************************
/*! \page nearblack nearblack

convert nearly black/white borders to black

\section msynopsis SYNOPSIS

\verbatim
nearblack [-white] [-near dist] [-nb non_black_pixels]
          [-o outfile] infile
\endverbatim

\section mdescription DESCRIPTION

This utility will scan an image and try to set all pixels that are nearly
black (or nearly white) around the collar to exactly black (or white).  This
is often used to "fix up" lossy compressed airphotos so that color pixels
can be treated as transparent when mosaicing. 

<dl>
<dt> <b>-o</b> <i>outfile</i>:</dt><dd> The name of the output file to be
created.  Newly created files are currently always created with the HFA driver
(Erdas Imagine - .img)</dd>
<dt> <b>-white</b>:</dt><dd> 
Search for nearly white (255) pixels instead of nearly black pixels.
</dd>
<dt> <b>-near</b> <i>dist</i>:</dt><dd> 
Select how far from black (or white) the pixel values can be and still considered near black (white).  Defaults to 15. 
</dd>
<dt> <b>-nb</b> <i>non_black_pixels</i>:</dt><dd> 
number of non-black pixels that can be encountered before the giving up search inwards. Defaults to 2. 
</dd>
<dt> <i>infile</i>:</dt><dd> 
The input file.  Any GDAL supported format, any number of bands, normally 8bit 
Byte bands.
</dd>
</dl>

The algorithm processes the image one scanline at a time.  A scan "in" is done 
from either end setting pixels to black (white) until at least 
"non_black_pixels" pixels that are more than "dist" gray levels away from 
black (white) have been encountered at which point the scan stops.  The nearly
black (white) pixels are set to black (white). The algorithm also scans from
top to bottom and from bottom to top to identify indentations in the top or bottom.

The processing is all done in 8bit (Bytes).

If the output file is omitted, the processed results will be written back
to the input file - which must support update. 

\if man
\section mauthor AUTHORS
Frank Warmerdam <warmerdam@pobox.com>
\endif
*/

*******************************************************************************
/*! \page gdal_merge gdal_merge.py

mosaics a set of images

\section gsynopsis SYNOPSIS

\verbatim
gdal_merge.py [-o out_filename] [-of out_format] [-co NAME=VALUE]*
                     [-ps pixelsize_x pixelsize_y] [-separate] [-v] [-pct]
                     [-ul_lr ulx uly lrx lry] [-n nodata_value] [-init "value [value...]"]
                     [-ot datatype] [-createonly] input_files
\endverbatim

\section gdescription DESCRIPTION

This utility will automatically mosaic a set of images.  All the images must
be in the same coordinate system and have a matching number of bands, but 
they may be overlapping, and at different resolutions. In areas of overlap,
the last image will be copied over earlier ones.

<dl>
<dt> <b>-o</b> <i>out_filename</i>:</dt><dd> The name of the output file,
which will be created if it does not already exist (defaults to "out.tif").</dd>
<dt> <b>-of</b> <i>format</i>:</dt><dd> 
Output format, defaults to GeoTIFF (GTiff). 
</dd>
<dt> <b>-co</b> <i>NAME=VALUE</i>:</dt><dd> 
Creation option for output file.  Multiple options can be specified.
</dd>
<dt> <b>-ot</b> <i>datatype</i>:</dt><dd> 
Force the output image bands to have a specific type. Use type names (ie. Byte, Int16,...)
</dd>
<dt> <b>-ps</b> <i>pixelsize_x pixelsize_y</i>:</dt><dd> Pixel size to be used for the
output file.  If not specified the resolution of the first input file will
be used.</dd>
<dt> <b>-ul_lr</b> <i>ulx uly lrx lry</i>:</dt><dd> The extents of the output file. 
If not specified the aggregate extents of all input files will be
used.</dd>
<dt>
<dt> <b>-v</b>:</dt><dd> Generate verbose output of mosaicing operations as they are done.</dd>
<dt> <b>-separate</b>:</dt><dd> 
Place each input file into a separate <i>stacked</i> band. 
</dd>
<dt> <b>-pct</b>:</dt><dd> 
Grab a pseudocolor table from the first input image, and use it for the output.
Merging pseudocolored images this way assumes that all input files use the same
color table.
</dd>
<dt> <b>-n</b> <i>nodata_value</i>:</dt><dd> 
Ignore pixels from files being merged in with this pixel value. 
</dd>
<dt> <b>-init</b> <i>value</i>:</dt><dd> 
Pre-initialize the output image bands with these values.  However, it is not
marked as the nodata value in the output file.  If only one value is given, the
same value is used in all the bands. 
</dd>
<dt> <b>-createonly</b>:</dt><dd> 
The output file is created (and potentially pre-initialized) but no input
image data is copied into it.  
</dd>
</dl>

NOTE: gdal_merge.py is a Python script, and will only work if GDAL was built
with Python support.

\if man
\section gauthor AUTHORS
Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer <silke@intevation.de>
\endif
*/

*******************************************************************************
/*! \page gdal2tiles gdal2tiles.py

generates directory with TMS tiles, KMLs and simple web viewers

\section gdal2tiles_synopsis SYNOPSIS

\verbatim
gdal2tiles.py [-title "Title"] [-publishurl http://yourserver/dir/]
              [-nogooglemaps] [-noopenlayers] [-nokml]
              [-googlemapskey KEY] [-forcekml] [-v]
              input_file [output_dir]
\endverbatim

\section gdal2tiles_description DESCRIPTION

This utility generates a directory with small tiles and metadata, following
OSGeo Tile Map Service Specification. Simple web pages with viewers based on
Google Maps and OpenLayers are generated as well - so anybody can comfortably
explore your maps on-line and you do not need to install or configure any
special software (like mapserver) and the map displays very fast in the
webbrowser. You only need to upload generated directory into a web server.

GDAL2Tiles creates also necessary metadata for Google Earth (KML
SuperOverlay), in case the supplied map uses EPSG:4326 projection.

World files and embedded georeference is used during tile generation, but you
can publish a picture without proper georeference too. 

<dl>
<dt> <b>-title</b> <i>"Title"</i>:</dt>
  <dd>Title used for generated metadata, web viewers and KML files.</dd>
<dt> <b>-publishurl</b> <i>http://yourserver/dir/</i>:</dt>
  <dd>Address of a directory into which you are going to upload the result. It should end with slash.</dd>
<dt> <b>-nogooglemaps</b>:</dt>
  <dd>Do not generate Google Maps based html page.</dd>
<dt> <b>-noopenlayers</b>:</dt>
  <dd>Do not generate OpenLayers based html page.</dd>
<dt> <b>-nokml</b>:</dt>
  <dd>Do not generate KML files for Google Earth.</dd>
<dt> <b>-googlemapskey</b> <i>KEY</i>:</dt>
  <dd>Key for your domain generated on Google Maps API web page (http://www.google.com/apis/maps/signup.html).</dd>
<dt> <b>-forcekml</b></dt>
  <dd>Force generating of KML files. Input file must use EPSG:4326 coordinates!</dd>
<dt> <b>-v</b></dt>
  <dd> Generate verbose output of tile generation.</dd>
</dl>


NOTE: gdal2tiles.py is a Python script that needs to be run against "new generation" Python GDAL binding.

\if man
\section gdal2tiles_author AUTHORS
Klokan Petr Pridal <klokan@klokan.cz> as a Google SoC 2007 Project.
\endif
*/

*******************************************************************************
/*! \page gdal-config gdal-config

determines various information about a GDAL installation

\section csynopsis SYNOPSIS

\verbatim
gdal-config [OPTIONS]
Options:
        [--prefix[=DIR]]
        [--libs]
        [--cflags]
        [--version]
        [--ogr-enabled]
        [--formats]
\endverbatim

\section cdescription DESCRIPTION

This utility script (available on Unix systems) can be used to determine
various information about a GDAL installation.  It is normally just used
by configure scripts for applications using GDAL but can be queried by an
end user. 

<dl>
<dt> <b>--prefix</b>:</dt><dd> the top level directory for the GDAL
installation.</dd>
<dt> <b>--libs</b>:</dt><dd> The libraries and link directives required to
use GDAL.</dd>
<dt> <b>--cflags</b>:</dt><dd> The include and macro definition required to compiled
modules using GDAL.</dd>
<dt> <b>--version</b>:</dt><dd> Reports the GDAL version.</dd>
<dt> <b>--ogr-enabled</b>:</dt><dd> Reports "yes" or "no" to standard output depending
on whether OGR is built into GDAL.</dd>
<dt> <b>--formats</b>:</dt><dd> Reports which formats are configured into GDAL 
to stdout.  
</dd>
</dl>

*/

*******************************************************************************
/*! \page gdal_retile gdal_retile.py

gdal_retile.py retiles a set of tiles and/or build tiled pyramid levels

\if man
\section retile_synopsis SYNOPSIS
\endif

\htmlonly
Usage:
\endhtmlonly

\verbatim

gdal_retile.py [-v] [-co NAME=VALUE]* [-of out_format] [-ps pixelWidth pixelHeight]
               [-ot  {Byte/Int16/UInt16/UInt32/Int32/Float32/Float64/
                      CInt16/CInt32/CFloat32/CFloat64}]'
               [ -tileIndex tileIndexName [-tileIndexField tileIndexFieldName]]
               [ -csv fileName [-csvDelim delimiter]]
               [-s_srs srs_def]  [-pyramidOnly]
               [-r {near/bilinear/cubic/cubicspline/lanczos}]
               -levels numberoflevels
               -targetDir TileDirectory input_files

\endverbatim
\if man
\section retile_description DESCRIPTION
\endif

This utility will retile a set of input tile(s). All the input tile(s) must
be georeferenced in the same coordinate system and have a matching number of bands.
Optionally pyramid levels are generated. It  is  possible to generate  shape file(s) for the tiled output.

If your number of input tiles exhausts the command line buffer, use the general --optfile option


<dl>
<dt> <b>-targetDir</b> <i>directory</i>:</dt><dd>
The Directory where the tile result is created. Pyramids are stored
in  subdirs  numbered  from  1. Created tile names have a numbering
schema and contain the name of the source tiles(s)
</dd>
<dt> <b>-of</b> <i>format</i>:</dt><dd>
Output format, defaults to GeoTIFF (GTiff).
</dd>
<dt> <b>-co</b> <i>NAME=VALUE</i>:</dt><dd>
Creation option for output file.  Multiple options can be specified.
</dd>
<dt> <b>-ot</b> <i>datatype</i>:</dt><dd>
Force the output image bands to have a specific type. Use type names (ie. Byte, Int16,...)
</dd>
<dt> <b>-ps</b> <i>pixelsize_x pixelsize_y</i>:</dt><dd> Pixel size to be used for the
output file.  If not specified, 256 x 256 is the default
</dd>
<dt> <b>-levels</b> <i>numberOfLevels</i>:</dt><dd>
Number of pyramids levels to build.
</dd>
<dt> <b>-v</b>:</dt><dd>
Generate verbose output of tile operations as they are done.
</dd>
<dt> <b>-pyramidOnly</b>:</dt><dd>
No retiling, build only the pyramids
</dd>
<dt> <b>-r</b> <i>algorithm</i>:</dt><dd>
Resampling algorithm, default is near
</dd>
<dt> <b>-s_srs</b> <i>srs_def</i>:</dt><dd>
Source spatial reference to use. The coordinate systems  that  can  be
passed  are  anything  supported by the OGRSpatialReference.SetFro‐mUserInput()  call,
which  includes  EPSG  PCS  and   GCSes   (ie.EPSG:4296),  PROJ.4  declarations (as above),
or the name of a .prf file containing well known text.
If  no  srs_def  is  given,  the srs_def  of the source tiles is used (if there is any).
The srs_def will be propageted to created tiles (if possible) and  to  the  optional
shape file(s)
</dd>
<dt> <b>-tileIndex</b> <i>tileIndexName</i>:</dt><dd>
The name of shape file containing the result tile(s) index
</dd>
<dt> <b>-tileIndexField</b> <i>tileIndexFieldName</i>:</dt><dd>
The name of the attribute containing the tile name
</dd>
<dt> <b>-csv</b> <i>csvFileName</i>:</dt><dd>
The name of the csv file containing the tile(s) georeferencing information.
The file contains 5 columns: tilename,minx,maxx,miny,maxy
</dd>
<dt> <b>-csvDelim</b> <i>column delimiter</i>:</dt><dd>
The column delimter used in the csv file, default value is a semicolon ";"
</dd>
</dl>

NOTE: gdal_merge.py is a Python script, and will only work if GDAL was built
with Python support.

\if man
\section retile_author AUTHORS
Christian Mueller <christian.mueller@nvoe.at>
\endif
*/

*******************************************************************************
/*! \page gdal_grid gdal_grid

creates regular grid from the scattered data

\section gdal_grid_synopsis SYNOPSIS

\verbatim
Usage: gdal_grid [--help-general] [--formats]
    [-ot {Byte/Int16/UInt16/UInt32/Int32/Float32/Float64/
          CInt16/CInt32/CFloat32/CFloat64}]
    [-of format] [-co "NAME=VALUE"]
    [-zfield field_name]
    [-a_srs srs_def] [-spat xmin ymin xmax ymax]
    [-l layername]* [-where expression] [-sql select_statement]
    [-txe xmin xmax] [-tye ymin ymax] [-outsize xsize ysize]
    [-a algorithm[:parameter1=value1]*] [-q]
    <src_datasource> <dst_filename>
\endverbatim

\section gdal_grid_description DESCRIPTION

This program creates regular grid (raster) from the scattered data read from
the OGR datasource. Input data will be interpolated to fill grid nodes with
values, you can choose from various interpolation methods. 

<dl>

<dt> <b>-ot</b> <i>type</i>:</dt><dd> For the output bands to be of the
indicated data type.</dd>

<dt> <b>-of</b> <i>format</i>:</dt><dd> Select the output format.  The default
is GeoTIFF (GTiff).  Use the short format name.</dd>

<dt> <b>-txe</b> <em>xmin xmax</em>:</dt><dd> Set georeferenced
X extents of output file to be created.</dd>

<dt> <b>-tye</b> <em>ymin ymax</em>:</dt><dd> Set georeferenced
Y extents of output file to be created.</dd>

<dt> <b>-outsize</b> <i>xsize ysize</i>:</dt><dd> Set the size of the
output file in pixels and lines.</dd>

<dt> <b>-a_srs</b> <i>srs_def</i>:</dt><dd> Override the projection for the
output file.  The <i>srs_def</i> may be any of the usual GDAL/OGR forms,
complete WKT, PROJ.4, EPSG:n or a file containing the WKT. </dd>

<dt> <b>-zfield</b> <i>field_name</i>:</dt><dd> Identifies an attribute field
on the features to be used to get a Z value from. This value overrides Z value
read from feature geometry record (naturally, if you have a Z value in
geometry, otherwise you have no choice and should specify a field name
containing Z value).</dd>

<dt> <b>-a</b> <i>[algorithm[:parameter1=value1][:parameter2=value2]...]</i>:
</dt><dd> Set the interpolation algorithm or data metric name and (optionally)
its parameters. See \ref gdal_grid_algorithms and \ref gdal_grid_metrics
sections for further discussion of available options.</dd>

<dt> <b>-spat</b> <i>xmin ymin xmax ymax</i>:</dt><dd> Adds a spatial filter
to select only features contained within the bounding box described by
(xmin, ymin) - (xmax, ymax).</dd>

<dt> <b>-clipsrc</b><em> [xmin ymin xmax ymax]|WKT|datasource|spat_extent</em>:
</dt><dd> Adds a spatial filter to select only features contained within the
specified bounding box (expressed in source SRS), WKT geometry (POLYGON or
MULTIPOLYGON), from a datasource or to the spatial extent of the <b>-spat</b>
option if you use the <em>spat_extent</em> keyword. When specifying a
datasource, you will generally want to use it in combination of the
<b>-clipsrclayer</b>, <b>-clipsrcwhere</b> or <b>-clipsrcsql</b>
options.</dd>

<dt> <b>-clipsrcsql</b> <em>sql_statement</em>:</dt><dd>Select desired
geometries using an SQL query instead.</dd>

<dt> <b>-clipsrclayer</b> <em>layername</em>:</dt><dd>Select the named layer
from the source clip datasource.</dd>

<dt> <b>-clipsrcwhere</b> <em>expression</em>:</dt><dd>Restrict desired
geometries based on attribute query.</dd>

<dt> <b>-l</b> <em>layername</em>: </dt><dd> Indicates the layer(s) from the
datasource that will be used for input features.  May be specified multiple
times, but at least one layer name or a <b>-sql</b> option must be
specified.</dd>

<dt> <b>-where</b> <em>expression</em>: </dt><dd> 
An optional SQL WHERE style query expression to be applied to select features 
to process from the input layer(s). </dd>

<dt> <b>-sql</b> <em>select_statement</em>: </dt><dd> 
An SQL statement to be evaluated against the datasource to produce a
virtual layer of features to be processed.</dd>

<dt> <b>-co</b> <i>"NAME=VALUE"</i>:</dt><dd> Passes a creation option to the
output format driver.  Multiple <b>-co</b> options may be listed.  See format 
specific documentation for legal creation options for each format.</dd>

<dt> <b>-q</b>:</dt><dd> Suppress progress monitor and other non-error
output.</dd>

<dt> <em>src_datasource</em>: </dt><dd> 
Any OGR supported readable datasource.</dd>

<dt> <em>dst_filename</em>: </dt><dd> 
The GDAL supported output file.</dd>

</dl>

\section gdal_grid_algorithms INTERPOLATION ALGORITHMS

There are number of interpolation algorithms to choose from.

\subsection gdal_grid_algorithms_invdist invdist

Inverse distance to a power. This is default algorithm. It has following
parameters:

<dl>
<dt><i>power</i>:</dt> <dd>Weighting power (default 2.0).</dd>
<dt><i>smoothing</i>:</dt> <dd>Smoothing parameter (default 0.0).</dd>
<dt><i>radius1</i>:</dt> <dd>The first radius (X axis if rotation angle is 0)
of search ellipse. Set this parameter to zero to use whole point array.
Default is 0.0.</dd>
<dt><i>radius2</i>:</dt> <dd>The second radius (Y axis if rotation angle is 0)
of search ellipse. Set this parameter to zero to use whole point array.
Default is 0.0.</dd>
<dt><i>angle</i>:</dt> <dd>Angle of search ellipse rotation in degrees
(counter clockwise, default 0.0).</dd>
<dt><i>max_points</i>:</dt> <dd>Maximum number of data points to use. Do not
search for more points than this number. This is only used if search ellipse
is set (both radiuses are non-zero). Zero means that all found points should
be used. Default is 0.</dd>
<dt><i>min_points</i>:</dt> <dd>Minimum number of data points to use. If less
amount of points found the grid node considered empty and will be filled with
NODATA marker. This is only used if search ellipse is set (both radiuses are
non-zero). Default is 0.</dd>
<dt><i>nodata</i>:</dt> <dd>NODATA marker to fill empty points (default
0.0).</dd>
</dl>

\subsection gdal_grid_algorithms_average average

Moving average algorithm. It has following parameters:

<dl>
<dt><i>radius1</i>:</dt> <dd>The first radius (X axis if rotation angle is 0)
of search ellipse. Set this parameter to zero to use whole point array.
Default is 0.0.</dd>
<dt><i>radius2</i>:</dt> <dd>The second radius (Y axis if rotation angle is 0)
of search ellipse. Set this parameter to zero to use whole point array.
Default is 0.0.</dd>
<dt><i>angle</i>:</dt> <dd>Angle of search ellipse rotation in degrees
(counter clockwise, default 0.0).</dd>
<dt><i>min_points</i>:</dt> <dd>Minimum number of data points to use. If less
amount of points found the grid node considered empty and will be filled with
NODATA marker. Default is 0.</dd>
<dt><i>nodata</i>:</dt> <dd>NODATA marker to fill empty points (default
0.0).</dd>
</dl>

Note, that it is essential to set search ellipse for moving average method. It
is a window that will be averaged when computing grid nodes values.

\subsection gdal_grid_algorithms_nearest nearest

Nearest neighbor algorithm. It has following parameters:

<dl>
<dt><i>radius1</i>:</dt> <dd>The first radius (X axis if rotation angle is 0)
of search ellipse. Set this parameter to zero to use whole point array.
Default is 0.0.</dd>
<dt><i>radius2</i>:</dt> <dd>The second radius (Y axis if rotation angle is 0)
of search ellipse. Set this parameter to zero to use whole point array.
Default is 0.0.</dd>
<dt><i>angle</i>:</dt> <dd>Angle of search ellipse rotation in degrees
(counter clockwise, default 0.0).</dd>
<dt><i>nodata</i>:</dt> <dd>NODATA marker to fill empty points (default
0.0).</dd>
</dl>

\section gdal_grid_metrics DATA METRICS

Besides the interpolation functionality \ref gdal_grid can be used to compute
some data metrics using the specified window and output grid geometry. These
metrics are:

<dl>

<dt><i>minimum</i>:</dt> <dd>Minimum value found in grid node search
ellipse.</dd>

<dt><i>maximum</i>:</dt> <dd>Maximum value found in grid node search
ellipse.</dd>

<dt><i>range</i>:</dt> <dd>A difference between the minimum and maximum values
found in grid node search ellipse.</dd>

<dt><i>count</i>:</dt> <dd> A number of data points found in grid node search
ellipse.</dd>

<dt><i>average_distance</i>:</dt> <dd>An average distance between the grid
node (center of the search ellipse) and all of the data points found in grid
node search ellipse.</dd>

<dt><i>average_distance_pts</i>:</dt> <dd>An average distance between the data
points found in grid node search ellipse. The distance between each pair of
points within ellipse is calculated and average of all distances is set as a
grid node value.</dd>

</dl>

All the metrics have the same set of options:

<dl>

<dt><i>radius1</i>:</dt> <dd>The first radius (X axis if rotation angle is 0)
of search ellipse. Set this parameter to zero to use whole point array.
Default is 0.0.</dd>
<dt><i>radius2</i>:</dt> <dd>The second radius (Y axis if rotation angle is 0)
of search ellipse. Set this parameter to zero to use whole point array.
Default is 0.0.</dd>
<dt><i>angle</i>:</dt> <dd>Angle of search ellipse rotation in degrees
(counter clockwise, default 0.0).</dd>
<dt><i>min_points</i>:</dt> <dd>Minimum number of data points to use. If less
amount of points found the grid node considered empty and will be filled with
NODATA marker. This is only used if search ellipse is set (both radiuses are
non-zero). Default is 0.</dd>
<dt><i>nodata</i>:</dt> <dd>NODATA marker to fill empty points (default
0.0).</dd>

</dl>

\section gdal_grid_csv READING COMMA SEPARATED VALUES

Often you have a text file with a list of comma separated XYZ values to work
with (so called CSV file). You can easily use that kind of data source in \ref
gdal_grid. All you need is create a virtual dataset header (VRT) for you CSV
file and use it as input datasource for \ref gdal_grid. You can find details
on VRT format at <a href="ogr/drv_vrt.html">Virtual Format</a> description
page.

Here is a small example. Let we have a CSV file called <i>dem.csv</i>
containing

\verbatim
Easting,Northing,Elevation
86943.4,891957,139.13
87124.3,892075,135.01
86962.4,892321,182.04
87077.6,891995,135.01
...
\endverbatim

For above data we will create <i>dem.vrt</i> header with the following
content:

\verbatim
<OGRVRTDataSource>
    <OGRVRTLayer name="dem">
        <SrcDataSource>dem.csv</SrcDataSource> 
	<GeometryType>wkbPoint</GeometryType> 
	<GeometryField encoding="PointFromColumns" x="Easting" y="Northing" z="Elevation"/> 
    </OGRVRTLayer>
</OGRVRTDataSource>
\endverbatim

This description specifies so called 2.5D geometry with three coordinates X, Y
and Z. Z value will be used for interpolation. Now you can use <i>dem.vrt</i>
with all OGR programs (start with \ref ogrinfo to test that everything works
fine). The datasource will contain single layer called <i>"dem"</i> filled
with point features constructed from values in CSV file. Using this technique
you can handle CSV files with more than three columns, switch columns, etc.

If your CSV file does not contain column headers then it can be handled in the
following way:

\verbatim
<GeometryField encoding="PointFromColumns" x="field_1" y="field_2" z="field_3"/>
\endverbatim

<a href="ogr/drv_csv.html">Comma Separated Value</a> description page contains
details on CSV format supported by GDAL/OGR.

\section gdal_grid_example EXAMPLE

The following would create raster TIFF file from VRT datasource described in
\ref gdal_grid_csv section using the inverse distance to a power method.
Values to interpolate will be read from Z value of geometry record.

\verbatim
gdal_grid -a invdist:power=2.0:smoothing=1.0 -txe 85000 89000 -tye 894000 890000 -outsize 400 400 -of GTiff -ot Float64 -l dem dem.vrt dem.tiff
\endverbatim

The next command does the same thing as the previos one, but reads values to
interpolate from the attribute field specified with <b>-zfield</b> option
instead of geometry record. So in this case X and Y coordinates are being
taken from geometry and Z is being taken from the <i>"Elevation"</i> field.

\verbatim
gdal_grid -zfield "Elevation" -a invdist:power=2.0:smoothing=1.0 -txe 85000 89000 -tye 894000 890000 -outsize 400 400 -of GTiff -ot Float64 -l dem dem.vrt dem.tiff
\endverbatim

\if man
\section gdal_grid_author AUTHORS
Andrey Kiselev <dron@ak4719.spb.edu>
\endif
*/


*******************************************************************************
/*! \page gdaldem gdaldem

Tools to analyze and visualize DEMs. (since GDAL 1.7.0)

\section gdaldem_synopsis SYNOPSIS

\htmlonly
Usage:
\endhtmlonly

\verbatim

- To generate a shaded relief map from any GDAL-supported elevation raster :
    gdaldem hillshade input_dem output_hillshade
                [-z ZFactor (default=1)] [-s scale* (default=1)]"
                [-az Azimuth (default=315)] [-alt Altitude (default=45)]
                [-b Band (default=1)] [-of format] [-co "NAME=VALUE"]* [-q]

- To generate a slope map from any GDAL-supported elevation raster :
    gdaldem slope input_dem output_slope_map"
                [-p use percent slope (default=degrees)] [-s scale* (default=1)]
                [-b Band (default=1)] [-of format] [-co "NAME=VALUE"]* [-q]

- To generate an aspect map from any GDAL-supported elevation raster
  Outputs a 32-bit float raster with pixel values from 0-360 indicating azimuth :
    gdaldem aspect input_dem output_aspect_map"
                [-trigonometric] [-zero_for_flat]
                [-b Band (default=1)] [-of format] [-co "NAME=VALUE"]* [-q]

- To generate a color relief map from any GDAL-supported elevation raster
    gdaldem color-relief input_dem color_text_file output_color_relief_map
                [-alpha] [-exact_color_entry | -nearest_color_entry]
                [-b Band (default=1)] [-of format] [-co "NAME=VALUE"]* [-q]
    where color_text_file contains lines of the format "elevation_value red green blue"
    
- To generate a Terrain Ruggedness Index (TRI) map from any GDAL-supported elevation raster:
    gdaldem TRI input_dem output_TRI_map
                [-b Band (default=1)] [-of format] [-q]
            
- To generate a Topographic Position Index (TPI) map from any GDAL-supported elevation raster:
    gdaldem TPI input_dem output_TPI_map
                [-b Band (default=1)] [-of format] [-q]
            
- To generate a roughness map from any GDAL-supported elevation raster:
    gdaldem roughness input_dem output_roughness_map
                [-b Band (default=1)] [-of format] [-q]

Notes :
  Scale is the ratio of vertical units to horizontal
   for Feet:Latlong use scale=370400, for Meters:LatLong use scale=111120)

\endverbatim
\if man
\section gdaldem_description DESCRIPTION
\endif

This utility has 7 different modes :
<dl>
<dt>\ref gdaldem_hillshade</dt><dd>to generate a shaded relief map from any GDAL-supported elevation raster</dd>
<dt>\ref gdaldem_slope</dt><dd>to generate a slope map from any GDAL-supported elevation raster</dd>
<dt>\ref gdaldem_aspect</dt><dd>to generate an aspect map from any GDAL-supported elevation raster</dd>
<dt>\ref gdaldem_color_relief</dt><dd>to generate a color relief map from any GDAL-supported elevation raster</dd>
<dt>\ref gdaldem_TRI</dt><dd>to generate a map of Terrain Ruggedness Index from any GDAL-supported elevation raster</dd>
<dt>\ref gdaldem_TPI</dt><dd>to generate a map of Topographic Position Index from any GDAL-supported elevation raster</dd>
<dt>\ref gdaldem_roughness</dt><dd>to generate a map of roughness from any GDAL-supported elevation raster</dd>
</dl>

The following general options are available :
<dl>
<dt> <i>input_dem</i>:</dt><dd> The input DEM raster to be processed</dd>
<dt> <i>output_xxx_map</i>:</dt><dd> The output raster produced</dd>
<dt> <b>-of</b> <i>format</i>:</dt><dd> Select the output format.  The default
is GeoTIFF (GTiff).  Use the short format name.</dd>
<dt> <b>-b</b> <i>band</i>:</dt><dd> Select an input <i>band</i> to be processed. Bands are numbered from 1.</dd>
<dt> <b>-co</b> <i>"NAME=VALUE"</i>:</dt><dd> Passes a creation option to the
output format driver.  Multiple <b>-co</b> options may be listed.  See format 
specific documentation for legal creation options for each format.</dd>
<dt> <b>-q</b>:</dt><dd> Suppress progress monitor and other non-error
output.</dd>
</dl>

\section gdaldem_modes Modes

\subsection gdaldem_hillshade hillshade

This command outputs an 8-bit raster with a nice shaded relief effect.
It’s very useful for visualizing the terrain.
You can optionally specify the azimuth and altitude of the light source,
a vertical exaggeration factor and a scaling factor to account for differences between vertical and horizontal units.

The following specific options are available :
<dl>
<dt> <b>-z</b> <i>zFactor</i>:</dt><dd>vertical exaggeration used to pre-multiply the elevations</dd>
<dt> <b>-s</b> <i>scale</i>:</dt><dd>ratio of vertical units to horizontal. If the horizontal unit of the source DEM is degrees (e.g Lat/Long WGS84 projection), you can use scale=111120 if the vertical units are meters (or scale=370400 if they are in feet)</dd>
<dt> <b>-az</b> <i>azimuth</i>:</dt><dd>azimuth of the light, in degrees. 0 if it comes from the top of the raster, 90 from the east, ... The default value, 315, should rarely be changed as it is the value generally used to generate shaded maps.</dd>
<dt> <b>-alt</b> <i>altitude</i>:</dt><dd>altitude of the light, in degrees. 90 if the light comes from above the DEM, 0 if it is raking light.</dd>
</dl>

\subsection gdaldem_slope slope

This command will take a DEM raster and output a 32-bit float raster with slope values.
You have the option of specifying the type of slope value you want: degrees or percent slope.
In cases where the horizontal units differ from the vertical units, you can also supply a scaling factor.

The following specific options are available :
<dl>
<dt> <b>-p</b> :</dt><dd>if specified, the slope will be expressed as percent slope. Otherwise, it is expressed as degrees</dd>
<dt> <b>-s</b> <i>scale</i>:</dt><dd>ratio of vertical units to horizontal. If the horizontal unit of the source DEM is degrees (e.g Lat/Long WGS84 projection), you can use scale=111120 if the vertical units are meters (or scale=370400 if they are in feet)</dd>
</dl>

\subsection gdaldem_aspect aspect

This command outputs a 32-bit float raster with values between 0° and 360° representing the azimuth that slopes are facing.
The definition of the azimuth is such that : 0° means that the slope is facing the North, 90° it's facing the East, 180° it's facing the South and
270° it's facing the West (provided that the top of your input raster is north oriented). The aspect value -9999 is used as the nodata value
to indicate undefined aspect in flat areas with slope=0.

The following specifics options are available :
<dl>
<dt> <b>-trigonometric</b>:</dt><dd> return trigonometric angle instead of azimuth. Thus 0° means East, 90° North, 180° West, 270° South</dd>
<dt> <b>-zero_for_flat</b>:</dt><dd> return 0 for flat areas with slope=0, instead of -9999</dd>
</dl>

By using those 2 options, the aspect returned by gdaldem aspect should be identical to the one of GRASS r.slope.aspect. Otherwise, it's identical
to the one of Matthew Perry's aspect.cpp utility.

\subsection gdaldem_color_relief color-relief

This command outputs a 3-band (RGB) or 4-band (RGBA) raster with values are computed from the elevation
and a text-based color configuration file, containing the association between various elevation
values and the corresponding wished color. By default, the colors between the given elevation values
are blended smoothly and the result is a nice colorized DEM. The -exact_color_entry or
-nearest_color_entry options can be used to avoid that linear interpolation for values that don't match an index
of the color configuration file.

The following specifics options are available :
<dl>
<dt> <i>color_text_file</i>:</dt><dd> text-based color configuration file</dd>
<dt> <b>-alpha</b> :</dt><dd>add an alpha channel to the output raster</dd>
<dt> <b>-exact_color_entry</b> :</dt><dd>use strict matching when searching in the color configuration file.
 If none matching color entry is found, the "0,0,0,0" RGBA quadruplet will be used</dd>
<dt> <b>-nearest_color_entry</b> :</dt><dd></dd>use the RGBA quadruplet corresponding to the closest entry in the color configuration file.</dd>
</dl>

The color-relief mode is the only mode that supports VRT as output format. In that case, it will translate the color configuration file into appropriate <LUT> elements. Note that elevations specified as percentage will be translated as absolute values, which must be taken into account when the statistics of the source raster differ from the one that was used when building the VRT.

The text-based color configuration file generally contains 4 columns per line : the elevation value and the
corresponding Red, Green, Blue component (between 0 and 255).
The elevation value can be any floating point value, or the <i>nv</i> keyword for the nodata value..
The elevation can also be expressed as a percentage : 0% being the minimum value found in the raster, 100% the maximum value.

An extra column can be optionnaly added for the alpha component. If it is not specified, full opacity (255) is assumed.

Various field separators are accepted : comma, tabulation, spaces, ':'.

Common colors used by GRASS can also be specified by using their name, instead of the RGB triplet. The supported list is :
white, black, red, green, blue, yellow, magenta, cyan, aqua, grey/gray, orange, brown, purple/violet and indigo.

Note: the syntax of the color configuration file is derived from the one supported by GRASS r.colors utility.
ESRI HDR color table files (.clr) also match that syntax.
The alpha component and the support of tablulations and commma as separators are GDAL specific extensions.

For example :
\verbatim
3500   white
2500   235:220:175
50%   190 185 135
700    240 250 150
0      50  180  50
nv     0   0   0   0 
\endverbatim

\subsection gdaldem_TRI TRI

This command outputs a single-band raster with values computed from the elevation.
TRI stands for Terrain Ruggedness Index, which is defined as the mean difference between a central pixel and its surrounding cells (see Wilson et al 2007, Marine Geodesy 30:3-35).

There are no specific options.

\subsection gdaldem_TPI TPI

This command outputs a single-band raster with values computed from the elevation.
TPI stands for Topographic Position Index, which is defined as the difference between a central pixel and the mean of its surrounding cells (see Wilson et al 2007, Marine Geodesy 30:3-35).

There are no specific options.

\subsection gdaldem_roughness roughness

This command outputs a single-band raster with values computed from the elevation.
Roughness is the the largest inter-cell difference of a central pixel and its surrounding cell, as defined in Wilson et al (2007, Marine Geodesy 30:3-35).

There are no specific options.


\section gdaldem_author AUTHORS
Matthew Perry <perrygeo@gmail.com>, Even Rouault <even.rouault@mines-paris.org>, Howard Butler <hobu.inc@gmail.com>, Chris Yesson <chris.yesson@ioz.ac.uk>

Derived from code by Michael Shapiro, Olga Waupotitsch, Marjorie Larson, Jim Westervelt :
U.S. Army CERL, 1993. GRASS 4.1 Reference Manual. U.S. Army Corps of Engineers,
Construction Engineering Research Laboratories, Champaign, Illinois, 1-425. 

\section gdaldem_seealso See also

Documentation of related GRASS utilities :

http://grass.osgeo.org/grass64/manuals/html64_user/r.slope.aspect.html

http://grass.osgeo.org/grass64/manuals/html64_user/r.shaded.relief.html

http://grass.osgeo.org/grass64/manuals/html64_user/r.colors.html

*/
