Shayne, Correct, for each height value in your DTED grid, you have to sample the EGM96 geoid at that point and add the two together. That will give you HAE. I don't know of any tools off the cuff, sorry. osgEarth has vertical datum support so you could probably write a tool using that.
Glenn Waldron / @glennwaldron / osgEarth On Thu, Sep 12, 2013 at 2:19 PM, Tueller, Shayne R Civ USAF AFMC 519 SMXS/MXDEC <[email protected]> wrote: > Glenn, > > VPB does reference to the WGS84 for the --geocentric option. > > So to do the conversion, do you have to remove the contribution of the > geoid > (gravitational equipotential surface) from the raw DTED first before > pumping > it into VPB? Is there an application that does this? > > Thanks, > -Shayne > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Glenn > Waldron > Sent: Thursday, September 12, 2013 12:04 PM > To: OpenSceneGraph Users > Subject: Re: [osg-users] [vpb] osgdem and HAE/MSL > > Nick, Shayne, > > I have not looked at VPB in a while, but I believe it expects height values > to be referenced to the WGS84 ellipsoid. If that's the case you'll need to > convert it first to HAE. > > By the way: DTED heights are referenced to the EGM96 geoid (not to the > WGS84 > ellipsoid). So they need conversion in order to be properly displayed. GDAL > (up until recently?) does not convey this information so there's no way for > the application to know. You just have to know :) > > > Glenn Waldron / @glennwaldron > > > On Thu, Sep 12, 2013 at 1:45 PM, Tueller, Shayne R Civ USAF AFMC 519 > SMXS/MXDEC <[email protected]> wrote: > > > Nick, > > Osgdem will work with the input elevation. It will build the > database based > on the input source. For example if you're using DTED and the > geocentric > option, it will place the point at the specified elevation (in > meters) above > the ellipsoid. The point is represented in the Cartesian ECEF > geocentric > space (e.g. x,y,z). > > The default ellipsoid used is WGS84. You can specify the polar and > equatorial radii in osgdem to fit to another ellipsoid. Just make > sure you > specify those radii in your EllipsoidModel class on the rendering > side so > that things match up. The EllipsoidModel class also defaults to > WGS84... > > HTH > > -Shayne > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of > Nick Modly > Sent: Sunday, August 25, 2013 11:46 PM > To: [email protected] > Subject: [osg-users] [vpb] osgdem and HAE/MSL > > Hi, > > When providing elevation data to osgdem. is it expected to be in > HAE > (height > above ellipoid), or MSL (mean sea level), or can it tell from the > input? For > example, I am providing elevation data in the AIG/Arc/Info Binary > Grid > format (.adf). The data represents the elevation of the area in > meters MSL. > However, when I osgpick a point and convert it to Lat-Lon-Alt MSL, > the > altitude is off by about 30m (the difference between HAE and MSL at > this > location). > > This are the options I ran osgdem with > $ osgdem --geocentric -o output.ive -l 8 -d ./path-to-dted/ -t > image.tif > > Is it possible to specify a vertical datum or coordinate system, > such as > EGM96? > > > Thank you! > > Cheers, > Nick > > ------------------ > Read this topic online here: > http://forum.openscenegraph.org/viewtopic.php?p=55984#55984 > > > > > > _______________________________________________ > osg-users mailing list > [email protected] > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > _______________________________________________ > osg-users mailing list > [email protected] > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > >
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