Make "Terrain inspector" tool less granular

This is a great tool, but it's kind of hard to use. Maybe other people use it for other things, but I mainly use it for figuring out how deep I need to dig and how far away/how many levels of retaining walls I'll need. At the edges of a deposit it tends to be sparse, meaning you can easily miss little bits of material since you have to go over 16 bits for every single mining designation.
I think it would be significantly more usable if it aggregated all the material for each square in the designation grid instead, so you have 1/16th as many points to check and can more easily find the edges & depths of deposits.
Also, I'm not 100% sure it's even working correctly as it is, since on rare occasions I've seen visual indications of coal or iron ore, but the terrain inspector doesn't show anything. I've also had times when I dig something out, check that I got all the resource I wanted, and fill it back in, only for the inspector to show bits of the resource I had just supposedly cleared.