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Re: MAP_PROJ_INIT [message #78190 is a reply to message #53364]

Sat, 29 October 2011 09:48

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

alx writes:

> My problem is actually the following: when applying the
> map_proj_forward function to real data,- that is to say when computing
> plane coordinates from given GPS longitudes and latitudes, a very
> standard operation from GPS data -, I find results wrong by a few
> hundred meters...
> For instance:
> IDL> lon0 = 2.1937863d0 & lat0 = 47.3808737d0
> IDL> map = map_proj_init(101, ELLIPSOID=24, ZONE=31)
> IDL> print, map_proj_forward(lon0, lat0)
> 439142.34 5247587.0
> Actual easting and northing (as calculated by using other tools) are
> 439144 and 5247806 instead.
> I then suspect somme error in map_proj_init, or maybe I am not using
> it correctly.
> I was wondering if other people had same experience.

Well, this is *exactly* the problem I was having this
week, and the "other tool" was ENVI. Maybe we are going
to have to look into this some more. What "other tools"
are you using?

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		map_proj_init By: marit on Sat, 07 April 2007 15:09
		Re: MAP_PROJ_INIT By: David Fanning on Sat, 29 October 2011 11:41
		Re: MAP_PROJ_INIT By: lecacheux.alain on Sat, 29 October 2011 11:10
		Re: MAP_PROJ_INIT By: lecacheux.alain on Sat, 29 October 2011 10:14
		Re: MAP_PROJ_INIT By: David Fanning on Sat, 29 October 2011 09:48
		Re: MAP_PROJ_INIT By: lecacheux.alain on Sat, 29 October 2011 08:27
		Re: MAP_PROJ_INIT By: David Fanning on Sat, 29 October 2011 07:18

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