WiFi access point location estimation
If I read your question correctly it's a relatively simple problem but a hard solution in the real world. 

Triangulation is your best bet at easily determining the location of the access point in theory, move to three points take the signal strength reading and bobs your uncle your access point is one the ceiling where you left it. 

But this has one critical flaw, your phone/measuring device needs an accurate frame of reference. If your indoors GPS has gone. So unless you whip out your tape measure and use some software to determine each of the three Triangulation spots accurately in 3d space it's a waste of your time. Even if you did have GPS I wouldn't call it accurate for the kind of distances that you require.