[Proj] Rectified Skew Orthomorphic projection, again...

Frank Warmerdam warmerdam at pobox.com
Wed Dec 16 00:55:47 EST 2009

Carl Godkin wrote:
> Hi,
> Almost 6 years ago I asked a question on this list (actually, a predecessor 
> list) about the rectified skew orthomorphic projection as used in Malaysia.
> http://lists.maptools.org/pipermail/proj/2004-January/001025.html
> I offered a patch which ended up as Bugzilla 461 to provide an 
> alternative to
> "omerc" called "rso" since the former was almost but not quite correct 
> for three
> batches of test points I had.
> At the time Frank said he'd wait for Gerald to weigh in on the situation
> which he did (as you could see from the email thread).  Gerald succeeded
> to producing the correct results by adding another parameter (which he 
> called 
> "gamma_c") to "omerc."
> I had meanwhile patched our copy of PROJ 4.4.7 (as I explained in the 
> Bugzilla entry) so I was happy.
> Here's where I made my mistake:
> When we updated PROJ versions, I assumed that Gerald's change was
> in the PROJ code.  I didn't realized that Gerald had apparently only made
> the change to support "gamma_c" (thus obviating my patch) to his libproj
> version, and not to PROJ.  (Until today when I started noticing the
> message about "gamma_c" not being used, I was unaware of this!)
> What should I do?  For now, I've just re-applied my old patch to a more
> recent version of PROJ and I'm getting the correct results again.  I
> guess the right thing to do would be to patch the "omerc" code as
> Gerald did, but I don't know how to do that and his code doesn't seem
> to be available anywhere any longer.


If you file a ticket, I'll try to port the gamma_c parameter from
libproj.4 and see if I can update the epsg to proj.4 translation to
capture this parameter.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

More information about the Proj mailing list