Selection by Location on Raster, Using a Vector Layer

Question

I'm trying to identify raster cells by location to eventually convert them to vector polygons, and then add them to an existing vector layer. Below is a picture to illustrate the problem.

The green layer is raster and the purple is the polygon. Is it possible to add raster cells that intersect the polygon within a given distance (notice how there are portions of the raster off to the far left that would be problematic if I just converted to a polygon now and then did a union). Ultimately I want to identify areas for a given distance, then be able to convert to vector so I can union it with the existing purple polygon.

Is this possible? Everything I've searched for regarding selection of raster suggests using Zonal Stats - but that's not necessarily what I'm trying to accomplish here. Any suggestions or alternatives?

Answer 1

I'm still a little confused about your end goal (polygonize all raster cells within a certain distance of the purple polygon?), but I think the Extraction toolbox in Spatial Analyst might be what you are looking for. You can either use the purple polygon as is, or buffer it (ex. "purple polygon + 100m around it"), and then use it as the input to Extract by Mask. If you need your final raster cells to be a polygon you could polygonize the output of Extract by Mask.

Polygonizing the raster originally and then Unioning it with the purple polygon would also work (Union doesn't care if the polygons extend far beyond each other), you would just need to do something like Select by Location in order to grab only the the Union-output polygons that are overlapped by the purple polygon (and ignore the polygons in the middle of the ocean).