topic Re: Discrepancy in measured distance between two point features and distance between point geometries built from their coordinates in ArcGIS API for Python Questions

Discrepancy in measured distance between two point features and distance between point geometries built from their coordinates

Glasnoct — Tue, 23 Jul 2024 20:15:32 GMT

I can't quite figure out how to reconcile the difference in reported footage between the following two methods. e.g.

feature1.distanceTo(feature2) -> 1,810 feet

and using the point returned by .firstPoint for each of the features:

def get_dist(coord1: tuple, coord2: tuple): sr = arcpy.SpatialReference(3418) p1 = arcpy.PointGeometry(arcpy.Point(coord1[0], coord1[1]), sr) p2 = arcpy.PointGeometry(arcpy.Point(coord2[0], coord1[1]), sr) return round(p1.distanceTo(p2), 3) -> ~1,760 feet

method 1 agrees with the measure distance tool but the second is off ~60 feet. This looks like a projection issue and I'm guessing that even though I build the point geometries with the same spatial reference as the features, that the coordinates returned from .firstPoint (lacking a spatial reference) are wrong. I don't need to do it this way very often but sometimes coordinates are what I have on hand at a certain point in the code and so I'm just trying to "rebuild" the feature's location to then get the distance from.

How can I keep the position I received from the feature accurate for when I rebuild the geometry?

Re: Discrepancy in measured distance between two point features and distance between point geometries built from their coordinates

DanPatterson — Tue, 23 Jul 2024 22:43:06 GMT

what is the spatial reference of the map if you are using the distance tool?

Re: Discrepancy in measured distance between two point features and distance between point geometries built from their coordinates

Glasnoct — Wed, 24 Jul 2024 13:11:33 GMT

map and feature layers are all using 4813 NAD 1983 StatePlane Iowa South FIPS 1402 (US Feet)

Re: Discrepancy in measured distance between two point features and distance between point geometries built from their coordinates

DanPatterson — Wed, 24 Jul 2024 14:11:34 GMT

I can't see anything here

Measure—ArcGIS Pro | Documentation

that would account for that difference if you are using 2d planar distance measurements

Re: Discrepancy in measured distance between two point features and distance between point geometries built from their coordinates

Glasnoct — Wed, 24 Jul 2024 18:33:40 GMT

I'm using the geodesic option, which agrees with the original geometry method.

edit: the reconstructed point distance is now reporting a distance identical to the original geometry distance. I don't believe I changed anything between yesterday and today. Perhaps when ArcPro was restarted this morning something ironed itself out. Glad I don't have to chase down this particular issue anymore. Thanks!

Re: Discrepancy in measured distance between two point features and distance between point geometries built from their coordinates

DanPatterson — Wed, 24 Jul 2024 18:44:48 GMT

I don't know what your point coordinates are, so do a hand calculation of the distance between the two points using pythagorean method and report which one it gives,

Also in

PointGeometry—ArcGIS Pro | Documentation

gives an alternate method which explicitly allows for geodesic distance calculation, give it a try as well

angleAndDistanceTo (other, {method})