Glenn
Posts: 2
Joined: Mon Apr 13, 2009 4:29 pm
Location: United Kingdom

Lambert coords to GPS?

Mon Apr 13, 2009 4:40 pm

Hi all, sorry if this has been asked previously - I have had a quick look but could not find anything close. I have purchased CoordTrans as (hopefully) the Holy Grail to something I have been struggling with for over 20 years, finding cave entrances in the French Alps.

I have the Lambert coords but using CoordTrans does not appear to give accurate translations for GPS. Using Grotte de la Luire (a show cave) as an example, the published coords are 844.4 x 3292.53, using Memory Map, the GPS (WGS84) coords are 31N 691973 x 4973756. Using CoordTrans 844.4 x 3292.53 (NTF France III - as that places it in roughly the correct place on the little map - nothing else does!) this gives a translation of 691425 x 4975507. What an I doing wrong?

Many thanks for any help.

Glenn

Glenn
Posts: 2
Joined: Mon Apr 13, 2009 4:29 pm
Location: United Kingdom

RE: Lambert coords to GPS?

Fri Jul 03, 2009 6:45 pm

Does the complete lack of a response mean that I can not convirt from Lambert to WGS84?

Cheers,

Glenn

Bilko83
Posts: 1
Joined: Tue Aug 04, 2009 11:31 pm
Location: USA

RE: Lambert coords to GPS?

Tue Aug 04, 2009 11:38 pm

Glenn,

I am only another user, but as I understand it the conversion list for the software is listed here:

http://franson.com/coordtrans/guide.asp?section=SupportedCountries&platform=winxp

Among that list you will find this entry under France:
France EuroLambert

I am no expert when it comes to Lambert projections, so I do not know if the listed grid matches your "Lambert". I just wanted to point this out. I do not see any other Lambert schemes listed for France on that page. I would suggest seeing if doing a conversion to another datum and then a performing second conversion to WGS84 solves your problem. This would at least be a check on whether the software has a bug going directly from Lambert to WGS84. If you do find a bug, I suggest posting here and e-mailing the developer.

Also, you might check here for some conversion formulas, not sure if it might help:

http://info.ogp.org.uk/geodesy/

Good luck.

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