Dynamically displaying polygon symbology by number of intersecting points as point layer updates using ArcGIS Pro

Question

I have a set of polygons (municipal boundaries) and a point layer. I'd like to (eventually) create a WebApp to show the number of points inside each municipality, but that point layer is going to be constantly updated (most likely each week).

I know a one time fix is a spatial join with number of intersection points as an attribute, but I was wondering if there was any method to query this sort of function to change as the point layer changes.

I want the symbology to update even if I add filters to the map. I could Python script it but that would only be for each write, where I want it to be truly dynamic.

Processes are planned to be done in ArcGIS Pro, but final product will be in ArcGIS Online

Answer 1

Visualising the point count in a Polygon dynamically in ArcGIS Online is not possible. According to the ArcGIS Arcade: Visualisation page, the Arcade expressions only allow access to the $feature and $view.scale attributes - in other words you cannot access the " Geometry Intersection" between the polygon and points using this methodology.

ArcGIS Arcade Documentation

That being said, you can use Arcade to access this interaction using a custom pop-up using this Arcade Expression:

var points = FeatureSetByName($map, 'Point_layer')
var countp = Count(Intersects(points,$feature))
return countp

So you will most likely need to pre-process this intersection in the publising of the polygon layer. Are you responsible / the owner of the polygon layer? You could set up a script using arcpy to run a "Summarise" or Intersect and Spatial Join before the layer is published. Then re-publish / update the feature layer when you need it updated.