For the longest part in a multipart polyline, use the line/part's midpoint to get the ID of the closest polygon
- Explode the multipart features
- Calculate a new field that tells you whether a singlepart line is the longest part of a multipart feature
var id = $feature.ORIG_FID
var fs = $featureset
var all_line_parts = Filter(fs, "ORIG_FID = @ID")
if($feature.Shape_Length == Max(all_line_parts, "Shape_Length")) {
return 1
}
return 0
- select and delete all exploded lines where "LongestLine = 0"
- Calculate the central point coordinates
- This is not actually the midpoint. This is what the tool help says:
- "This point is the same as the centroid if the centroid is inside the feature, otherwise it is an inner label point."
- But it's probably the best you're going to get without pretty large code blocks...
- Convert to points
- export to actual point feature class
Find nearby polygon features
- Join MidPoints to the original Line FC using "OBJECTID = ORIG_FID"
- Add the polygons to that join, using "MidPoints.NEAR_FID = OBJECTID"
- Calculate the PolygonID field
- Remove all joins
Thanks Dan. Regarding your question, "Why are the roads multipart to begin with?"
Answer:
Some of the roads are multi-part due to situations like this:
The road's "Exclusive Right Turn" lane was deemed to be too short to be it's own asset. So it was merged into it's parent asset as a multipart feature:
(Here's an example photo, although not the same one from the screenshot above: https://i.stack.imgur.com/aiL7W.png)
That decision was made years ago by people other than me and is beyond my control. (It's not possible to change things at this point...there are too many existing dependencies. Splitting the multipart into two single parts would compromise any records that are related. Including an already-integrated work order management system.)
The other scenario is:
Multipart features were created by accident. The person who digitized the roads merged two lines together, but didn't realize that a multipart feature was created.
In that case, it might be possible to go back and convert the multiparts to single parts. But it would take a lot of work to review/fix any linear referencing events that are tied to the geometry/M-values of those roads.
I've submitted an idea about multiparts here: Prevent multi-part features.
Does that answer your first question?
I'll answer your second question about "Why you need to know the closest Ward polygons to each midpoint of the longest part?" in a separate comment. Cheers.
