[Proj] apply plane rotation after transverse Mercator projection

Garret Duffy garret.duffy at nuigalway.ie
Thu Oct 13 04:09:23 EST 2011

Yes, I've tried the omerc projection with +rot_conv and +no_uoff but the
issue is the alpha azimuth parameter is actually the angle of the rotated
cylinder about the ellipsoid (I think the limits are +/- 90?  Can anyone
confirm??) and this angle bears little or no relation to the azimuth of the
projected y-axis relative to true north.  I tried making a bunch of
projections with different alpha angles and +rot_conv and +no_uoff but is
was very hard to precisely control the rotation of the linear features I was
interested in measuring.

I think this thread involving Mikael and Frank discusses it well


It appears that the gamma parameter should actuate an XY_PLANE_ROTATION...

So this leads to two question and one request:

Q1) does omerc take the gamma parameter now? I am running v. 4.5

Q2) what are the limits of alpha?

R3) Would it be possible to design a new CRS similar to tmerc but taking a
gamma parameter?

Thanks everyone for your advice.

"Mikael Rittri" <Mikael.Rittri at carmenta.com> wrote in message
news:11AC4CEB-F5B7-45A1-BE18-730A3FABD1C2 at carmenta.com...
The Rosenmund projection is called +proj=somerc (Swiss Oblique Mercator),
but I don't see why that should be better than the RSO (+proj=omerc) for
this purpose.

I don't think there is any built-in support in Proj.4 to do an arbitrary
rotation of the projected plane.
However, if you just need to rotate 90, 180 or 270 degrees, then you could
perhaps use the +axis parameter.

Best regards,

Mikael Rittri

Den 12 okt 2011 kl. 15:53 skrev "Clifford J Mugnier" <cjmce at lsu.edu>:

I don't know if PROJ4 has it, but the Rosenmund projection as used in
Switzerland sounds like what you want.

Clifford J. Mugnier, C.P., C.M.S.
Chief of Geodesy,
Center for GeoInformatics
Department of Civil Engineering
Patrick F. Taylor Hall 3531
Baton Rouge, LA  70803
Voice and Facsimile:  (225) 578-8536 [Academic]
Voice and Facsimile:  (225) 578-4578 [Research]
Cell: (225) 328-8975 [Academic & Research]
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Fellow Emeritus of the ASPRS
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From: proj-bounces at lists.maptools.org on behalf of Duffy, Garret
Sent: Wed 12-Oct-11 06:13
To: proj at lists.maptools.org
Subject: [Proj] apply plane rotation after transverse Mercator projection

I would like to design a projection that is similar to a TM projection
except append the parameter "XY_Plane_Rotation", i.e. rotate the XY axes.
Is this possible to do in PROJ4?  I note the tmerc doesn't have an alpha
parameter or similar.  I already tried using RSO but it's overkill for what
I want to do, all I want to do is apply a simple cartesian rotation to the
projected XY axes.
Another thing I tried was editing a PRJ file for a TM projected data and
then appending "PARAMETER["XY_Plane_Rotation",XX]" to the file but that
doesn't seem to work.
Do I have to define a custom PROJCS that is based on tmerc but allows for
the XY_Plane_Rotation parameter?
Any suggestions gratefully would be (very) gratefully received as I have
been trying to do this supposedly simple thing all week.
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