Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

When I project longitude -60, latitude 0 to mercator, I get the expected answer:

> echo "-60 0" | cs2cs +proj=lonlat +to +proj=merc
-6679169.45     0.00 0.00 

However, when I project it to oblique mercator with very similar parameters, I get a very different result:

> echo "-60 0" | cs2cs +proj=lonlat +to +proj=omerc +k=1.0 +lat_0=0 +alpha=0.0001 +lonc=0.00001
-8416502.68     -4.68 0.00

Shouldn't the results be approximately equal?

I couldn't use exactly 0 for parameters, since omerc won't initialize there.

I sense I'm doing omerc wrong: what's the right way?

EDIT: I am aware that omerc might have a minor bug for alpha<0: but this shouldn't affect what I'm doing.

share|improve this question

Your Answer


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

Browse other questions tagged or ask your own question.