topic Re: What is the proper way to reproject a geometry object using arcpy? in Python Questions

What is the proper way to reproject a geometry object using arcpy?

EricEagle — Fri, 10 Dec 2021 23:25:04 GMT

I am working with a geometry object projected in EPSG 6455 but would like to add its extent to a feature class that is in EPSG 4326.

arcpy.Project_management() wants a feature class as input and output.

Here's what I've got so far (please note that using ZLAS is in no way an endorsement of ZLAS as a proprietary format)

### ZLAS testing ###
zlas = "C:/Data/USGS_LPC_IL_4County_Cook_2017_LAS_15008550_LAS_2019.zlas"

des = arcpy.Describe(zlas)

print(des.dataType)
print(des.spatialReference.factoryCode)
print(des.extent)

polys = []

las_extent = [
            [
                [des.extent.YMin, des.extent.XMin],
                [des.extent.YMax, des.extent.XMin],
                [des.extent.YMax, des.extent.XMax],
                [des.extent.YMin, des.extent.XMax]
            ]
        ]
for coord_ring in las_extent:
    poly = arcpy.Polygon(arcpy.Array([arcpy.Point(*coords) for coords in coord_ring]), arcpy.SpatialReference(6455))
    polys.append(poly)

How would I coerce "poly" from 6455 to 4326 without incurring the IO expense of writing feature classes?

The background, if useful: I am plowing through a directory structure with thousands and thousands of point clouds. The intent is to gather their extents, add them to a global feature class, and then serve that feature class up as a service identifying where all of our holdings are, allowing users to browse our holdings geographically rather than trying to hunt through a directory tree. Because many of the files are projected differently (some requiring transformation - default transformation being fine as this isn't high precision) I want to harmonize them all into a single GCS feature class.

Re: What is the proper way to reproject a geometry object using arcpy?

DanPatterson — Wed, 10 Jun 2020 17:31:14 GMT

Like this example in

Polygon—ArcPy classes | Documentation

projectAs (spatial_reference, {transformation_name})

Parameter	Explanation	Data Type
spatial_reference	The new spatial reference. This can be a SpatialReference object or the coordinate system name.	SpatialReference
transformation_name	The geotransformation name.	String

Re: What is the proper way to reproject a geometry object using arcpy?

EricEagle — Wed, 10 Jun 2020 17:43:46 GMT

Thanks Dan... Sometimes one just needs a pointer to the right doc. I tell ya, if the Esri UC was happening this year I'd hunt you down and buy you an adult beverage of your choice. Really appreciate all the help.

Re: What is the proper way to reproject a geometry object using arcpy?

DanPatterson — Wed, 10 Jun 2020 18:19:46 GMT

I will be online