We are trying to use proj4 to project a local coordinate system to EPSG4326. We believe we have most of the string created correctly in QGIS and as follows;

+proj=ortho +datum=WGS84 +lat_0=40.52741251 +lon_0=-117.12455304 +x_0=372979.646 +y_0=103881.838 +units=us-ft no_defs

We are missing azimuth and scale. I believe we can use +k or _k_0 for scale but cannot determine how azimuth is defined. Are these incorporated into such a projection in proj4? We have also run the ESRI equivalent prj through GDAL srsinfo with the following output:

PROJ.4 : ERROR 6: No translation for LOCAL to PROJ.4 format is known.

Local system params in ESRI.prj;

Projection: Local
Scale_Factor:   1.00024937
Azimuth:    -0.31500000

The Proj.4 definition of the orthographic projection does not use scale or azimuth values: http://geotiff.maptools.org/proj_list/orthographic.html

If you need a rotated local coordinate system, you better use an oblique mercator projection.

See my answer to this topic for an example: Using customized Coordinate System in ArcGIS Desktop?

See also:




In the last source, you can read that the ESRI Local projection suffers heavy distortion away from the center, so changing the projection to omerc is not a bad idea.


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