You're correct that Meraki needs at least three access points to triangulate client location. You will get more reliable location data within the area defined by your set of access points (technically, within the two-dimensional convex hull defined by your access points). Outside of that area, Meraki tries to determine a location, but the results aren't as good as you'll see inside the area. If you want really good location data, you should think about every possible position on your property. At each point, consider four directional quadrants. You want an access point in 3 out of those 4 quadrants within a range of about 3m to 25m (not the exact numbers, just from memory). You won't get a perfect layout, but this is a way to approximate the quality of your plan from a location accuracy perspective.
... View more