[steve86]

A laptop, GPS and a mag-mount 2.4 GHz antenna is a fun way to engage in some "wardriving" to find all the "open" APs in the area.

I don't know if you really do that because a handheld yagi is much more useful than a magnetic mount omni antenna for that purpose. Obviously, you know that in principle from your HAM experience.

[Myrddin]

The mag-mount omni builds an RSSI profile for each AP. Samples are taken and matched with the current lat/lon from the GPS. The RSSI contour gives a decent approximation of the location of the AP. Ham radio APRS does better than that. It purposely broadcasts the GPS lat/lon of the transmitter.

I put a GPS receiver, 802.11b Ethernet converter and Kyocera M200 (1xRTT) on each of my research rail cars. The PC104 (linux) computer sets up a PPP link to VerizonWireless. As the cars move around the country, they send a GPS lat/lon/timestamp/battery voltage to my web server in Mclean, VA. That allows me to track the cars and create a coverage profile for VerizonWireless. The cars employ OLSR mesh networking so telemetry to/from the locomotive can traverse the train even when line of sight is lost around a curve. The link state up update 5 times per second. As a proactive mesh network it provides minimal latency for time critical controls. Connectivity to devices on the car is accomplished with a CAN network at 125 KHz.