[Openstreetmap-dev] WGS84/UTM/Lambda... Projection library

Immanuel Scholz immanuel.scholz at gmx.de
Mon Sep 19 22:30:11 BST 2005


> A little while back, I ported a crufty but decent (1980's) C projection
> library from the Defense Mapping agency. It does the UTM projections
> with all of the various popular ellipsoids.

Cool, just the stuff I was looking for.
At least for the UTM part. Well, other projection systems can wait until
I really see maps for them and until I am convinced, that the precision
difference is more than the monitor resolution here ;-)

> The port is in Ruby, so if you would consider using a real language ;)
> <troll, troll, troll> you could just call it:
> http://www.openstreetmap.org/websvn/filedetails.php?repname=OpenStreetMap&path=%2Futils%2Ftiger_import%2Ftiger%2Futm.rb

Phe! Don't think some missing semicolon and brackets or some wrong
clauses can scare me off. ;-)


Well, two things: First, although both algorithm claim to do the same,
yours and the JEEP one provide slightly different projections, off by
about 1° of rotation. :-?  Well, we'll see whose algo maps better on
some background images ;)

Second, a minor thing to consider in line 196, which is:

      phi1 = phi1_rad * RAD_TO_DEG

What is phi1 for? It is never used again.. (Which my precious Java (!)
development environment instantly detected and made me remove the
resource consumpting line by one click. <rant><rant> hehe.. ;)

Ciao, Imi

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