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Commit d788cd8b authored by Julien Michel's avatar Julien Michel
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DOC: Describing precisely the behaviour of the DEMHandler class

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......@@ -60,16 +60,51 @@ namespace otb
{
/** \class DEMHandler
*
* \brief Class for Reading a DEM data
* \brief Single access point for DEM data retrieval
*
* This class is the single configuration and access point for
* elevation handling in images projections and localisation functions.
* elevation handling in images projections and localisation
* functions. Since this class is a singleton, the New() method is
* deprecated and will be removed in future release. Please use the
* DEMHandler::Instance() method instead.
*
* Please be aware that a proper instanciation and parameter setting
* of this class is advised before any call to geometric filters or
* functionalities. Ossim internal accesses to elevation are also
* configured by this class and this will ensure consistency
* throughout the library.
*
* The class allows to configure a directory containing DEM tiles
* (DTED or SRTM supported) using the OpenDEMDirectory() method. The
* OpenGeoidFile() method allows to input a geoid file as well. Last,
* a default height above ellipsoid can be set using the
* SetDefaultHeightAboveEllipsoid() method.
*
* The class allows to retrieve either height above ellipsoid or
* height above Mean Sea Level (MSL).
*
* Here is the complete description of both methods outpout depending
* on the class configuration for the SRTM DEM (in the following, no
* SRTM means DEMDirectory not set, or no coverage for point, or
* srtm_value is no_data).
*
* It is based on ossimElevManager.
* It allows to obtain height above Ellipsoid or MSL(Mean Sea Level)
* of a geographic point.
* GetHeightAboveEllipsoid():
* - SRTM and geoid both available: srtm_value + geoid_offset
* - No SRTM but geoid available: geoid_offset
* - SRTM available, but no geoid: srtm_value
* - No SRTM and no geoid available: default height above ellipsoid
*
* GetHeightAboveMSL():
* - SRTM and geoid both available: srtm_value
* - No SRTM but geoid available: BUGGY CASE (returns NaN)
* - SRTM available, but no geoid: srtm_value
* - No SRTM and no geoid available: default height above ellipsoid
*
* It handles both DTED and SRTM formats.
* Please note that OSSIM internal calls for sensor modelling use the
* height above ellipsoid, and follow the same logic as the
* GetHeightAboveEllipsoid() method.
*
* DEM directory can either contain DTED or SRTM formats.
* \ingroup Images
*
*/
......
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