Le 31/05/2023 à 01:24, Javier Jimenez Shaw a écrit :
Thanks Even for the quick response.
Can I create a CRS as WKT with the ob_tran?
in a PROJ-specific way, yes:
$ bin/projinfo "+proj=ob_tran +o_proj=moll +o_lon_p=40 +o_lat_p=50
+lon_0=60 +type=crs"
PROJ.4 string:
+proj=ob_tran +o_proj=moll +o_lon_p=40 +o_lat_p=50 +lon_0=60 +type=crs
WKT2:2019 string:
PROJCRS["unknown",
BASEGEOGCRS["unknown",
DATUM["World Geodetic System 1984",
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1]],
ID["EPSG",6326]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8901]]],
CONVERSION["unknown",
METHOD["PROJ ob_tran o_proj=moll"],
PARAMETER["o_lon_p",40,
ANGLEUNIT["degree",0.0174532925199433,
ID["EPSG",9122]]],
PARAMETER["o_lat_p",50,
ANGLEUNIT["degree",0.0174532925199433,
ID["EPSG",9122]]],
PARAMETER["lon_0",60,
ANGLEUNIT["degree",0.0174532925199433,
ID["EPSG",9122]]]],
CS[Cartesian,2],
AXIS["(E)",east,
ORDER[1],
LENGTHUNIT["metre",1,
ID["EPSG",9001]]],
AXIS["(N)",north,
ORDER[2],
LENGTHUNIT["metre",1,
ID["EPSG",9001]]],
REMARK["PROJ CRS string: +proj=ob_tran +o_proj=moll +o_lon_p=40
+o_lat_p=50 +lon_0=60"]]
On Wed, 31 May 2023, 00:43 Even Rouault, <[email protected]>
wrote:
Javier,
I suspect you might be able to apply the azimuth by using the
infamous +proj=ob_tran. The tricky part will be to find on which
parameter(s) of ob_tran (o_lat_p, o_lon_p, lon_0) to map it.
Possibly relevant, there's at least 2 different code
implementations attempting at reproducing the Spilhaus from Esri,
which include a azimuth parameter:
- cf https://github.com/OSGeo/PROJ/issues/1851#issuecomment-943138537
- or
https://github.com/neocarto/bertin/blob/main/src/projections/spilhaus.js
+ https://github.com/d3/d3-geo/blob/main/src/rotation.js
The maths ressemble those of proj=ob_tran
Even
Le 31/05/2023 à 00:24, Javier Jimenez Shaw a écrit :
Hi
Some use cases of Esri "local" projection are arriving to my
desk. This projection works in Esri software, but not in PROJ
(obviously also not in QGIS)
One example is this WKT1_ESRI
PROJCS["Hycroft001",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Local"],PARAMETER["False_Easting",13264.924],PARAMETER["False_Northing",46473.418],PARAMETER["Scale_Factor",1.00025],PARAMETER["Azimuth",15.786],PARAMETER["Longitude_Of_Center",-116.7048269],PARAMETER["Latitude_Of_Center",42.88212865],UNIT["Foot_US",0.3048006096012192]]
Looking at their documentation, it seems to be this one:
https://desktop.arcgis.com/en/arcmap/latest/map/projections/local.htm
The biggest difference I see with the Orthographic from PROJ is
the Azimut parameter. I have the impression that the azimut is
just a rotation of the axes, but it is not clear to me in the
Snyder book (page 145. If you do not have it, it is available at
https://pubs.er.usgs.gov/publication/pp1395 )
Is there are alternative in PROJ?
Does it make sense to add this transformation?
Thanks
Javier
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