How to convert SRTM to ellipsoidal elevation?
SRTM data is distributed with referenced to the EGM96 geoid model (and hence have orthometric elevations) The GDAL command needed to convert the dataset is gdalwarp. We need to supply it with a source spatial reference system (s_srs) and a target spatial reference system (t_srs) values.
What is the difference between orthometric and ellipsoidal elevation?
Orthometric (or geoid) elevation measures height of a point from mean-sea-level (MSL). Ground based surveys will produce orthometric elevations Ellipsoidal elevation measures height of a point from a reference ellipsoid (such as WGS84).
What is the height above the reference ellipsoid?
The GPS uses height (h) above the reference ellipsoid that approximates the earth’s surface. The traditional, orthometric height (H) is the height above an imaginary surface called the geoid, which is determined by the earth’s gravity and approximated by MSL.
Which is digital elevation model has ellipsoidal elevation?
Cartosat-1 Digital Elevation Model (CartoDEM) is a National DEM developed by the Indian Space Research Organization (ISRO). It is derived from the Cartosat-1 stereo payload launched in May 2005. The Cartosat DEM is referenced to the WGS84 ellipsoid model (and hence have ellipsoidal elevation).
How to convert a Geoid vertical datum to an ellipsoid?
Convert from (EGM96) geoid vertical datum to (WGS84) ellipsoid vertical datum: You will need the gtx file containing vertical datum shifts from here: http://download.osgeo.org/proj/vdatum/egm96_15/
How to convert ellipsoidal elevation to orthometric elevation?
The GDAL command needed to convert the dataset is gdalwarp. We need to supply it with a source spatial reference system (s_srs) and a target spatial reference system (t_srs) values. A previous version of this article used EPSG codes to specify a compound CRS, such as EPSG:4326+5773.
How to convert EGM96 vertical CRS to GDAL?
In the example above, when we did the transformation to EGM96 vertical CRS, it used the parameters supplied in the egm96_15.gtx file. Many such grid files are included when you download and install GDAL. But there are other grids which are very large and are not included by default.