Hi Glenn; Not sure if I am allowed to distribute it, as Jeff didn't mention whether or not it was proprietary, etc. When I do this for small terrains in the stereographic or oblique stereographic alternative projection in proj4, I am pretty much right on, at least to the sub-second level in lat or long. The X, Y at the southwest corner, at least at the resolution of the pick, is around 0, 111120. The terrain is a 2x2 degree terrain, and the origin is one degree up on the west edge. The problem comes with larger terrains, I can be more than a minute off in latitude and longitude, and when I say large, I mean terrains that can be as big as 12 degrees by 12 degrees. Thanks, Lenny
________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Glenn Waldron Sent: Tuesday, December 16, 2008 1:55 PM To: OpenSceneGraph Users Subject: Re: [osg-users] Looking for some Terrex Terrapage Archive help Can I see the spreadsheet? What are the coordinates at the southwest corner of your terrain? Glenn Waldron : Pelican Mapping : http://pelicanmapping.com : +1.703.652.4791 On Tue, Dec 16, 2008 at 1:41 PM, Smith, Leonard C <[email protected]> wrote: Hi Glenn; Thanks for the ideas. I had quite a lengthy support discussion with a gentleman from Terrex, and he informed me that they were using the proj4 library in the projection, that it was on the WGS84 ellipsoid, and more, including that the projection is WGS84 flat earth, and sent me a spreadsheet with a whole slew of information. The projInfo.txt file looks like this: csm=Projected originlat=25.000000000000000 originlon=42.000000000000000 zunits=1.000000000000000 selectorId=60000 dcType=NONE dcSelectorId=0 txpOffsetX=0.000000 txpOffsetY=0.000000 txpOffsetZ=0.000000 And here is one of his replies, which didn't nail down the question of "what is the projection". I got a "looks like the projection is", not a "the projection is": Lenny, The answer is Yes to your question: Just to touch base again, it looks like the projection we are talking about (from what I can gather looking at the projections) is an orthographic projection at the origin that the user specifies. Is that correct? Sorry for the delay. Jeff Again, thanks for your help, Lenny ________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Glenn Waldron Sent: Tuesday, December 16, 2008 1:04 PM To: OpenSceneGraph Users Subject: Re: [osg-users] Looking for some Terrex Terrapage Archive help Leonard, It's highly unlikely that a Terrapage model would be in an orthographic or stereographic projection. I'm pretty sure Terrex can only support localized projections like UTM and state plane. If you are trying to guess what CS the terrain is in, take a lat/long you know is on the terrain and figure out which UTM zone it's in. That's the first thing I would try. Also, if you have a projInfo.txt file, that might lend a clue. Glenn Waldron : Pelican Mapping : http://pelicanmapping.com : +1.703.652.4791 On Tue, Dec 16, 2008 at 9:08 AM, Smith, Leonard C <[email protected]> wrote: Hello All; I have been attempting over the last few months to invert the LVCS projection in a Terrex Terrapage archive (.txp) file to retrieve an accurate latitude, longitude, and altitude given the X, Y, and Z coordinates in the file. I have tried the proj4 library, with a stereographic projection, and an orthographic projection, to no avail. I have had some success with smaller areas, for instance 2 degrees in latitude and 2 degrees in longitude, but with larger areas, the pj_inv function fails to give me accurate results. Does anyone have any information as to just what projection parameters the LVCS projection is, such as "+proj=stere +R=", or the like? For an example, if I have a latitude of 31 North and a longitude of 49 East, I have tried the following two projections, and both fail to give me accurate results: "+proj=ortho +lat_0=31N +lon_0=49E" "+proj=stere +lat_0=31N +lon_0=49E" Thanks for any help, Leonard Smith _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.or g _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.or g
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