The +no_uoff flags, needed for some Oblique Mercators, have disappeared from nad/epsg
|Reported by:||mikrit||Owned by:||warmerdam|
In Proj version 4.7 and in the trunk, there are no longer any +no_uoff flags in any omerc definitions in nad/epsg.
I think they were present in Proj version 4.6.1 (see http://trac.osgeo.org/proj/ticket/37 and 38).
A +no_uoff ("no u-offset") means that the origin is at the so-called natural origin, on the central oblique line of the projection, and near the ordinary equator (on the "aposphere equator", but I've never understood what an aposphere is). This is called Hotine Oblique Mercator Variant A (new terminology, from the EPSG Guidance Note 7.2 published Nov. 2010).
If the +no_uoff is omitted, you get Hotine Oblique Mercator Variant B instead, where the origin is at the projection center.
I noticed that you implemented the +gamma parameter for omerc last year, and this means that you can remove the old +rot_conv flag, but it seems you have thrown out the baby with the bath water: you cannot remove the +no_uoff flag from those omerc instances that are supposed to be variant A.
Change History (10)
comment:8 Changed 4 years ago by warmerdam
- Milestone set to 4.8.0
- Status changed from new to assigned