Oscium's WiPry-Pro can visualize wireless activity using what we call Real Time View. Beacon frames appear as either a parabolic or rectangular outline. This makes it easy to see adjacent or co-channel overlap. It is generally accepted that co-channel overlap is better than adjacent overlap. Co-channel overlap is when different AP's are on the exact same channel.
An example is provided below:
The SSID labelled "Free WiFi" has adjacent overlap with the following SSIDs: Test and Guest. No co-channel overlap is pictured because none of the AP's are on the exact same channel.