The drone will seek out and determine the approximate location of different available WiFi networks by using a combination of RSSI and SSID. Upon determination of the location (approximate) of the network AP, the coordinates will be logged and stored in NVM through the use of an on-board COTS GPS module. After a certain number of networks have been discovered (I haven't decided the threshold yet) the drone will return to base where the coordinates can be downloaded and plotted in a maps application.
Note: Obviously, this description is very high level. More details to come (i.e. HW, physical dimensions, etc.) in the near future.