The mag-mount antennas clipped to the back roof of my Honda Element just fine. I also picked up a Garmin GPS18 hockey-puck (the PC version with DB9 serial and 12v-in) and stuck it on the roof alongside. The antenna wires fit through the rubber gasket in the hatchback without too much fuss. For those of you who know groundplanes and antenna theory better than I: yes, I know that these are horrible positions that will cause a directional response. It's just a testing setup. :) A better antenna mounting will be found later.
The antennas survived a 70mph-plus-headwinds driving test so I wasn't too worried about them. The GPS and the soekris both had 12v cigarette lighter plugs for power which I plugged into a 4-into-1 adapter from the spare parts box. This plugged into the rear power socket of the Element (it has one in the cargo area, something I think all cars should have!) and gave it a fire-up, the laptop perched on the tailgate to watch the boot. Everything worked just fine on the car's power supply.
The box fit nicely into the seatback bunjees below the rear cargo cover. This kepts most of the electronics out of sight. So that the unit could run with the car off I stuck a Xantrex 400 battery pack in the cargo space and hooked it into the same 4-into-1 power bus. This way when the car runs its alternator charges the Xantrex and when it's off (and relay-isolated from the main car battery) the Xantrex supplies the power.
I closed up the car and took a walk around my neighborhood with the powerbook. That 8db antenna is great! Just doing a walking-around-while-pinging test and plotting it generically against a map, this is what the coverage zone approximates to:
The darker blue is where I was getting solid data. The lighter shade was where packetloss started. At some point I'm going to need to fire up kismet or some similar wardriver and do a real map around my house with the car parked in the dirveway like that.
The Soekris pulls about 15w. The GPS pulls a little less. Together the Xantrex would run them for about 12 hours before its built-in meter hit 0% (the safe limit, about 50% of the battery's capacity). Recharging was a matter of driving for about an hour or bringing the Xantrex inside to plug into the wall overnight. In the future I'll see about putting about 40-60w of solar panel on the car's bikerack. That should let it charge/run all day and run all night without any driving at all, given standard California summer sun and properly sun-mindful parking.
After ripping out NoCatAuth and putting basic network translation and a WEP key in its place, the system runs better than I thought it would! The unit is turning out to be quite handy:
Overall the system is a champ. Wherever my car goes, I have data! If it screws up the only maintenance it requires is being power-cycled -- which is pretty rare. As coverage increases and EVDO rolls out the speed of the link will improve drastically.
First things first: I wanted live GPS tracking. I've wanted to be able to do this for ar long time for no particularly good reason. It's just neat. :) GPSd to the rescue! With Pebble it's as easy as apt-get install gpsd once you're connected to the net. GPSd's purpose in life is toe listen to a serial-port, NMEA-based GPS (such as the Garmin 18 I bought) and re-share it as a network port. Garth coded up a quick php script on one of our servers that uses the dynamic DNS name of the device to remotely grab the lat/long from the GPS. A little XML massaging and trickery via the excellent Google Maps Standalone mode makes for a very nice vehicle tracking page. The page is only online when the car is (and when I'm willing to let others randomly see my location). Here's a screen-cap of it in operation:
Google maps is pretty slick in that it can give you aerial photography instead of a map if you wish. It makes for some seriously impressive demos. : Additionally, GPSd can use netDGPS to get differential signals and provide an incredibly accurate position without having to have a pricey (and huge-antenna-equipped) DGPS receiver.
Not happy to stop there, I wanted to have a live webcam of some sort. At 1xRTT it's not terribly feasable to have streaming video but uploading a picture every few minutes wouldn't be hard at all.
The easiest way to do this was with a wireless webcam. D-Link seems to make the lowest cost one that does what I want, with the DCS-900W. I stuck it on a Panavise mount on the back window of the car and added it into the wireless network. A CRON job runs on the soekris that pulls down a .jpg from the camera every five minutes. If the retrieve is successful it then sends it to a server back at my house to go with the tracking page. This way internet visitors who pull up the image aren't hitting the actual mobile link and bogging it down. Later when we get EVDO in my area I'll try to see if I can set up an echo-and-multiplex stream system to let internet users view a live video stream instead.
The camera worked pretty well at first though the dang suction-cup mount kept falling off due to the defroster-wires making for a !flat surface. Unfortunately it fried in the sunlight, overheating and dying nastily. The better solution is going to be an external "video router" that can take inputs from any kind of camera and output over eithernet or wireless. This way I can put a hardened camera anywhere I want in the car (or even multiple cameras) and use the same programs to serve up the images.
This should be good for security situations. If you point a camera inside at the driver's position (from, say, the headliner or dashboard) you can make the video router start recording upon motion-sense. It would constantly upload the results to an offsite server along with timestamp and GPS coordinates. Even if the thief ripped the system out it would get a few good frames of him/her and store them offsite. If the equipment is hidden correctly it'll give live GPS tracking and video to help with retrieval of the car.
