topic Re: find closest xy on a polyline from a point in ArcGIS API for Python Questions

find closest xy on a polyline from a point

StuartMoore — Wed, 08 Jan 2025 14:14:50 GMT

so this sounds simple and if i use Near in Pro it is but i want to create a AGOL python notebook to run once a day to loop over any point features created that day and get the closest XY to a feature service of polylines (50k features)

i tried following the example here Part 3 - Spatial operations on geometries | ArcGIS API for Python

but even if i just manually populate the geomenty json for both the point and the polyline it returns None

Re: find closest xy on a polyline from a point

DavidPike — Wed, 08 Jan 2025 19:25:54 GMT

Are you using a standard Notebook? I think you'd require an Advanced Notebook type to then be able to import the required ArcPy module.

access_res.type is probably returning none

Re: find closest xy on a polyline from a point

StuartMoore — Thu, 09 Jan 2025 09:39:49 GMT

thanks @DavidPike that was the issue

it looks like its returning the distance now but it looks like its in radians?

Re: find closest xy on a polyline from a point

StuartMoore — Thu, 09 Jan 2025 11:17:09 GMT

it also looks like its only getting the closest vertex rather than the closest point on the line unfortunately

Re: find closest xy on a polyline from a point

DavidPike — Thu, 09 Jan 2025 11:29:33 GMT

Are you able to share the full code and possibly the mapped polyline and point inputs and point result? Values look like a spatial reference issue, possibly. I don't think there's any angles calculated so likely not radians.

I found the Python API Geometry Class docs to be a bit confusing as they suggested a result being a tuple of xy coords and the distance.

Then I found this https://community.esri.com/t5/arcgis-api-for-python-questions/need-query-point-and-distance-clarification/td-p/1514270

which describes the actual result object (straight from the arcpy function). 😐

Re: find closest xy on a polyline from a point

StuartMoore — Thu, 09 Jan 2025 14:03:36 GMT

this is the code:

for xbsg in bsgPoints: print(xbsg.attributes["objectid"]) print(xbsg) access_point = Point(xbsg.geometry) access_res = access_polyline.query_point_and_distance(access_point) if (access_res): print(access_res) print("--++--") print(access_res[0].JSON) print("----")

this is the code's closest point

but i was expecting this as the closest point:

and this is the distances returned:

i also found that post and it suggests that the distance is the second item so

0.001106969364200805

Re: find closest xy on a polyline from a point

DavidPike — Thu, 09 Jan 2025 14:29:30 GMT

From the geometry methods doc and the doc screenshot in that thread, the 2nd value appears to be the distance from the line start along the line. I think it's the 3rd value you're looking for. Without knowing more about your data etc. I'm not sure what may be happening with the results.

I'd print out the JSON of the inputs also and maybe something with the SRID/WKID might show up.

https://desktop.arcgis.com/en/arcmap/latest/analyze/arcpy-classes/geometry.htm

Re: find closest xy on a polyline from a point

StuartMoore — Thu, 09 Jan 2025 14:36:36 GMT

this is the geometry of one of the polylines

{"geometry": {"paths": [[[-1.04626706475298, 52.5312679471987], ........ [-1.0447855316579, 52.5304270718345]]], "spatialReference": {"wkid": 4326, "latestWkid": 4326}}

this is the geometry for one of the points

{"geometry": {"x": -1.0453711186340822, "y": 52.53063399067387, "spatialReference": {"wkid": 4326, "latestWkid": 4326}}

thanks for the help

Stu

Re: find closest xy on a polyline from a point

DavidPike — Thu, 09 Jan 2025 14:41:49 GMT

OK that's WGS84 and the lengths I guess are decimal degrees. Unless there's another Geodesic Method available I think you'd really need to project the coordinates into a planimetric coordinate system to get a meaningful output.

Re: find closest xy on a polyline from a point

Clubdebambos — Thu, 09 Jan 2025 15:43:14 GMT

You can get the information for the output tuple from the ArcPy Polyline documentation.

Re: find closest xy on a polyline from a point

StuartMoore — Fri, 10 Jan 2025 09:22:24 GMT

thanks @DavidPike i changed the spatial reference when querying my layers and it works, even gives me the correct distance