nav[aria-label="Primary Navigation"] { padding: 0; & ul { list-style: none; width: 100%; display: flex; flex-direction: row; justify-content: start; align-items: start; gap: 30px; padding: 0; & li { margin: 0; } & ul li { list-style: none; } } }

determine area of polygon in "EPSG:3857"

artzaifman

I downloaded the US states shapefile from census.gov and imported "Texas" as follows:

geom = geometry.Geometry.from_shapely( us_states_.geometry[11], spatial_reference={"wkid": 3857} ) geom.area

956858520477.5554

geom = geomeUsing arcpy method "get_area" gave different answer:

geom.get_area("GEODESIC", units="SQUAREMETERS")

692662873864.4374

Main question is following: is it possible to have "geom.area" return value = "geom.get_area" return value?

Thank you!

Find more posts tagged with

Accepted answers

JoshuaBixby

Absolutely, that is if you want to rely on using Geometry.area . WKID 3857, like all conformal projections, is focused on maintaining direction and shape. Area and distance measurements can be very off, as you are seeing with TX. I think an old standby would be Albers Equal Area Conic USA (102003), but some of the new whole-earth projections from Esri work well like Equal Earth Americas (8858).

All comments

artzaifman

To close out this issue, sr=8858 works fantastically and here's the sq. meters of TX from "area" property:

692653163631.7217 (vs. 956858520477.5554 using sr=3857).

artzaifman

Great answer and thank you.

JoshuaBixby

artzaifman

Does it boil down to finding the best projection (with least distortion) when using "area" property as opposed to "get_area()" method in arcpy?

artzaifman

Only reason is "arcpy" is Windows and my development environment is Mac. I'm running "parallels" so that I can access both simultaneously.

JoshuaBixby

You seem to be getting the answer you are interested in using Geometry.get_area, so why not just use that?

artzaifman

Thanks Joshua. Is there additional information available that would explain how to convert from spatial reference unit area to measurement type?

JoshuaBixby

Short answer, no. When looking at the arcgis.geometry.Geometry — arcgis 1.8.0 documentation:

propertyarea
The area of a polygon feature. None for all other feature types. The area is in the units of the spatial reference.

get_area(method, units=None)
Returns the area of the feature using a measurement type.

You are downloading the geometry data into WKID 3857, so that is the spatial reference that Geometry.area will report its value in.

artzaifman

Reformatted errors in previous post:

I downloaded the US states shapefile from census.gov and imported "Texas" as follows:

geom = geometry.Geometry.from_shapely( us_states_.geometry[11], spatial_reference={"wkid": 3857} ) geom.area

956858520477.5554

Using arcpy method "get_area" gave different answer:

geom.get_area("GEODESIC", units="SQUAREMETERS")

692662873864.4374  # This is correct!

Main question is following: is it possible to have "geom.area" return value = "geom.get_area" return value?

Thank you!

Join the Conversation

Signed in members can post, follow updates, and more. New here? Register a free account.

Quick Links

Community Help
Find useful guides, FAQs, and documents to help you navigate and make the most of Esri Community.