Shapefile drop-in should select geometries; use centroid-based selection

[EricaMaurer]

Shapefile drop-in current provides only a boundary for visual comparison. It should also select geometries, using a centroid-based selection.

We still need to decide how this will work with concave geometries — centroids may either be those on the surface of the feature/polygons or based on the bbox. Once we clarify the exact selection strategy, we can move forward.

Shapefile drop-in currently produces erroneous selection-- missing geographies within shapefile drop-in & extra selected areas beyond shapefile boundaries.

User should be able to see selected areas that have a centroid within their shapefile boundary

[allthesignals]

Can I have some sample Shapefiles for testing purposes?

[hannahkates]

Will most likely use centroid method, but we'll explore other options. We'll also research Carto's methodology.

[andycochran]

Using centroids seems brittle to me, as a centroid often isn't within its polygon. I'd suggest we try programmatically changing the shapefile by putting a negative buffer on its polygons and making the selection using these shrunken polygons. This would prevent a polygon with a boundary that lies on a tract boundary from selecting the adjacent tract.

[allthesignals]

I think the way this feature works now makes this irrelevant, closing for now unless we should reopen

[EricaMaurer]

This may be something we want to revisit since we have heard from users that they'd like the application to select the geographies within their shapefile. This obviously doesn't work if they upload a shapefile that covers the entire city, but would work if it's a specific study area. Will keep it open for now.

[allthesignals]

Okay thanks @EricaMaurer I'll adjust the issue title and description so that it remains the place where we talk about shapefile-upload-as-selector.