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--></style></head><body bgcolor=white lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>Egm96 grid shift file available from http://download.osgeo.org/proj/vdatum/egm96_15/egm96_15.gtx<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Mike<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:10.5pt;color:black'>-- <o:p></o:p></span></p><div><p class=MsoNormal><span style='font-size:10.5pt;color:black'>Michael Smith<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.5pt;color:black'>Remote Sensing/GIS Center<o:p></o:p></span></p></div><p class=MsoNormal><span style='font-size:10.5pt;color:black'>US Army Corps of Engineers</span><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:12.0pt;color:black'>From: </span></b><span style='font-size:12.0pt;color:black'>gdal-dev <gdal-dev-bounces@lists.osgeo.org> on behalf of Even Rouault <even.rouault@spatialys.com><br><b>Date: </b>Tuesday, November 21, 2017 at 6:18 AM<br><b>To: </b><gdal-dev@lists.osgeo.org><br><b>Subject: </b>Re: [gdal-dev] Vertical datum conversion for SRTM data<o:p></o:p></span></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>On mardi 21 novembre 2017 10:25:42 CET Nikos Alexandris wrote:<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> Dear list, can GDAL handle the following exercise?<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> Of interest is the Mean Sea Level, based on NASA’s SRTM. I am new in this<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> topic. Is the following equation correct?<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> SRTM(MSL) = SRTM(WGS84) - MSL(WGS84) [*]<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> Is it “correct” to recommend the https://hydrosheds.cr.usgs.gov/ data<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> set for Mean Sea Level related studies? I refer specifically to i) 5.1<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> Void-filled digital elevation model and ii) 5.2 Hydrologically conditioned<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>> elevation [**]<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-paragraph-type:empty;-qt-block-indent:0'> <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>Not completely sure this answers your questions ,but this is related.<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-paragraph-type:empty;-qt-block-indent:0'> <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>Quoting end of http://www.gdal.org/gdalwarp.html:<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-paragraph-type:empty;-qt-block-indent:0'> <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>"""<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>(GDAL >= 2.2) To transform a DEM from geoid elevations (using EGM96) to WGS84 ellipsoidal heights:<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-paragraph-type:empty;-qt-block-indent:0'> <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>gdalwarp -overwrite in_dem.tif out_dem.tif -s_srs EPSG:4326+5773 -t_srs EPSG:4979<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>"""<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-paragraph-type:empty;-qt-block-indent:0'> <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>This assumes the egm96_15.gtx grid is in the proj.4 resource directory.<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-paragraph-type:empty;-qt-block-indent:0'> <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>-- <o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>Spatialys - Geospatial professional services<o:p></o:p></p><p style='margin:0in;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0'>http://www.spatialys.com<o:p></o:p></p><p class=MsoNormal>_______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev<o:p></o:p></p></div></body></html>