EPSG 9835 is an conversion method which needs some parameters defined: https://pyproj4.github.io/pyproj/stable/api/crs/coordinate_operation.html#lambertcylindricalequalareaconversion
You can use that conversion to build a projected CRS: https://pyproj4.github.io/pyproj/stable/build_crs.html#projected-crs That being said, you might also be interested in geodesic area if you have geographic coordinates: https://pyproj4.github.io/pyproj/stable/examples.html#geodesic-area And you can use this to get the Geod class for EPSG:4326: https://pyproj4.github.io/pyproj/stable/api/crs/crs.html#pyproj.crs.CRS.get_geod Hopefully this helps, Alan On Fri, Sep 18, 2020, 9:31 PM Mikhail Kruk <mes...@gmail.com> wrote: > Yes, you are correct, that was one of my first attempts and was wrong > because I don't really understand these projection systems. > I now have a better one which sort of works and produces areas in meters > by setting first system to > sr.SetWellKnownGeogCS("EPSG:4326") > Now I am struggling with selecting the projection coordinate system. Some > suggested that I use cylindrical projection EPSG:9835 which should > preserve the area anywhere on the planet but when I try > sr_proj.ImportFromEPSG(9835) > I get error: > PROJ: proj_create_from_database: crs not found > > > On Fri, Sep 18, 2020 at 9:50 PM Michael Patrick <geodes...@gmail.com> > wrote: > >> ... but basically I came to the conclusion that when people talk about an >>> area of something on Earth they really mean the area of a projection (am i >>> right about that?) and so i need to specify a projection before getting a >>> meaningful area. So i ended up with this code: >>> >>> wkt = "POLYGON ((lon1 lat1, lon2 lat2, lon3 lat3))" >>> poly = ogr.CreateGeometryFromWkt(wkt) >>> sr = osr.SpatialReference() >>> sr.SetWellKnownGeogCS("NAD83") >>> sr.SetProjCS("SRS_PT_TRANSVERSE_MERCATOR") >>> poly.AssignSpatialReference(sr) >>> poly.GetArea() <https://lists.osgeo.org/mailman/listinfo/gdal-dev> >>> >>> I might be dense, but it seems you are assigning sr as a specific >> transverse mercator, i.e. UTM zone 18N, or a custom one centered on the >> centroid of your polygon. i.e. you don't have sufficient arguments. >> >> >> >> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon> >> Virus-free. >> www.avast.com >> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link> >> <#m_-5507655572585127822_m_8065453534991225343_m_-2581199688950320765_m_6579958654730313444_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> >> _______________________________________________ >> gdal-dev mailing list >> gdal-dev@lists.osgeo.org >> https://lists.osgeo.org/mailman/listinfo/gdal-dev > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/gdal-dev
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