Vertical Datum and Landsat

Data.  This should be done over an ethernet connection.


The two USGS DEMs provide ground truth, for the "true" characteristics of the terrain.  We are also looking at the vertical datums.  Most of these come in 1 degrees tiles, and they have been modifited slightly for you (mainly so the file names indicate the data set).  The rest of the DEMs are free with global coverage; there are higher resolution commercial alternatives.

DEM--Description Spacing Source Producer Characteristics
NED/3DEP 1/3" Best available USGS Name of the file is the NW corner; others are the SW corner.  These still say NED, and the metadata says the name change was cosmetic only.
NED/3DEP 1" Best available USGS Name of the file is the NW corner; others are the SW corner.  Just better spatial resolution compared to 1/3".
SRTM 1" Radar NASA Does not cover high latitudes.
ALOS World 3D, AW3D30 1" Stereo pan imagery JAXA  
NASDADEM 1" Radar NASA Two beta versions, with and without hole filling;  Reprocessing of SRTM. 
ASTER GDEM 1" Stereo NIR imagery NASA / JAXA Goes closer to the poles than SRTM.
MERIT 3" Radar + stereo pan Univ. Tokyo Combines ASTER and SRTM.  This has 5 degree tiles. 
Tandem_X 3" Radar DLR Derived from much higer resolution data, only available commercially or by application for research. 

Load project There is a project file in the GLOBAL-DEMS folder which will all open the DEM all in one step.

You can deal with 5 degree square DEM.

Compare the global DEMs, using the NED/3DEP as ground truth.

Open DEM to open a geoid file, which will be in C:\mapdata\geology\geology_grids\egm2008.tif. (or open it from the Geology menu).   This shows  + values where the geoid is above the ellipsoid, and - values where the geoid is below the ellipsoid.  You can use this to do a vertical datum shift, but the geoid grid does not have to be open.

New image for the Landsat image.  Open all bands as a group by picking the TIF file for any one of them.

Landsat scene displays. 

Include the following 3D views with the Landsat draped over the DEM.  These will work best on a large map

  1. Anaglyph (ask instructor for glasses)
  2.   OpenGL 3D view.  If the icon is not available, set the DEM to use with the image on Modify menu
  3. Perspective views

Last revision 10/20/2018