Tell me more ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.
up vote 3 down vote favorite
1

I have QGIS with proj 4.8.0 installed. I'd like to add Winkel Tripel projection which seems to be defined as

+proj=wintri

But that definition string does not work. Is this a bug in my proj version, or what's the correct definition string?

share|improve this question
Works for me: echo "34 -34" | proj "+proj=wintri" – Paul Ramsey Nov 22 '12 at 4:17
1  
Yes, that echos something. But if I define a custom CRS with this string, nothing gets reprojected in QGIS. Guess I'd need some more parameters? – underdark♦ Nov 22 '12 at 6:42
No, the fact that it's re-projecting on the command-line seems to indicate it works. Is it possible that QGIS has a proj library bundled different from the one you think you have? Or that QGIS actually checks the projection strings itself before passing them on to proj? (And hasn't heard of Winkel yet?) – Paul Ramsey Nov 22 '12 at 14:40
2  
@Paul Ramsey: It seems that even though the Winkel Tripel projection is defined in the proj library and can be called from the command line, it can't be used as a custom CRS in QGIS because there's no inverse transformation in the proj library (see lists.maptools.org/pipermail/proj/2012-May/006302.html). And it seems that the inverse transformation isn't trivial (and will always be an approximation...). – Jake Nov 23 '12 at 16:17
2  
I think you should write that into an answer, as it is... the answer. The command-line tools also refuse to do an inverse projection. – Paul Ramsey Nov 23 '12 at 17:39

Know someone who can answer? Share a link to this question via email, Google+, Twitter, or Facebook.

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.