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Author Topic: proj4 definition not match with WKT EPSG 2056  (Read 1574 times)

Phogi

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proj4 definition not match with WKT EPSG 2056
« on: March 10, 2020, 06:07:22 AM »
Hello Alexey,

I found the EPSG: 2056 in Metashape returned different proj string to the WKT:
Proj4:

'+proj=omerc +lat_0=46.95240555555561 +lonc=7.439583333333329 +alpha=90 +gamma=90 +k_0=1 +x_0=2600000 +y_0=1200000 +ellps=bessel +units=m

WKT:
'PROJCS["CH1903+ / LV95",GEOGCS["CH1903+",DATUM["CH1903+",SPHEROID["Bessel 1841",6377397.155,299.1528128,AUTHORITY["EPSG","7004"]],TOWGS84[674.374,15.056,405.346,0,0,0,0],AUTHORITY["EPSG","6150"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9102"]],AUTHORITY["EPSG","4150"]],PROJECTION["Oblique_Mercator",AUTHORITY["EPSG","9815"]],PARAMETER["latitude_of_center",46.95240555555561],PARAMETER["longitude_of_center",7.439583333333329],PARAMETER["azimuth",90],PARAMETER["recitified_grid_angle",90],PARAMETER["scale_factor",1],PARAMETER["false_easting",2600000],PARAMETER["false_northing",1200000],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AUTHORITY["EPSG","2056"]]'

From http://epsg.io/2056 the projection in proj4 should be +proj=somerc rather than +proj=omerc. It's interesting that the conversion is correct, so I assume the conversion is not using proj4 string is it?

Thanks

Phogi

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Re: proj4 definition not match with WKT EPSG 2056
« Reply #1 on: March 18, 2020, 04:05:56 AM »
Hi Alexey,

It seems the WKT is different shown to the proj4 string returned, can you check if the projection parameters are correct?

Best,

Alexey Pasumansky

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Re: proj4 definition not match with WKT EPSG 2056
« Reply #2 on: March 18, 2020, 07:09:32 PM »
Hello Phogi,

Thank you for mentioning, we'll check the proj4 line generation in Metashape. It is generated from the current crs and is not used anyhow, so shouldn't affect the processing.
Best regards,
Alexey Pasumansky,
Agisoft LLC