Putting your GPS on the Net

The Goal

The goal of this project was to create a cheap, simple GPS tracking system using cheap hardware and free/and or home grown software. In a nutshell, a PC grabs the coordinates off a locally attached GPS device, uploads them with the use a Verizon EVDO wireless card to a web server that stores the coordinates in a MySQL database. Then, anyone on the Net can go to a web page (http://unstable.aset.psu.edu/cjh/gps/ in this case) and see where I am at in the world. The web page utilizes the Google Maps API and AJAX to track updates in real time. Such a device could be placed in a car, Faculty shuttle or loop bus. An entire setup with dedicated PC costs around $700. If you choose not to go with a dedicated PC, it would just cost the price of a GPS receiver and a cell card.

The Box

Originally, I used my Macbook Pro to read the coordinates off the GPS receiver. This works great if you don't want to buy a dedicated piece of hardware. After successfully prototyping the system with my laptop, I decided to buy one of those mini-PCs that are designed for use in cars. These mini-PC's continue to get faster, cheaper and less power hungry all the time. When wired properly, the box will turn on with your ignition and turn off when your car is turned off. I settled on the SolidLogic 3677 Mini-ITX Car System case which houses a mini-ITX main board manufactured by Via Technologies. The EIPA MII 12000 motherboard was chosen because it includes both a CardBus slot (for the cell card) and a CompactFlash slot (for the OS). The box runs Linux (Debian as the distribution).

The GPS

Any GPS that uses the NMEA protocol should be sufficient. There are three GPSes that I tested successfully. They are Garmin Etrex Legend, Garmin Mobile 10 and the Delorme Earthmate LT-20. To see if the GPS you have is supported by GPSD, check out the matrix here. More on GPSD later.

The Cellular Card

All you really need is an IP connection to upload the coordinates. Any cell card, reliable municipal wifi (though this will severely limit your range) or cell phone data connection would work perfectly fine. We purchased a Verizon PC5200 card, because the mini-ITX box only has a CardBus slot (it doesn't have an expresscard/34 like the Macbook Pro). An unlimited data plan from Verizon runs about $70/month.

The Mapping

The Google maps API is very well written and very easy to use. You have to sign up for a google maps API key before you can start using it on your web site. You can obtain one here. Including a good map into web page only requires a few lines of HTML and javascript.

The Software

Information from the GPS is recieved via some open source software called gpsd. I wrote some C code that you can get here. Some C code grabs the info from gpsd and uploads the coordinates via a simple HTTP GET request. The OS that runs on the mini-PC is linux (Debian, in this case but anything will do). The machine boots up, connects to the internet via pppd, and starts uploading coordinates once it aquires enough satellites. It will reconnect to the network if it loses its connection. It's works very well. So far, I have logged almost 100,000 coordinates in the database.

Source Code

There is some code you need to download:

1. gpsd
2. C code to retrieve GPS coordinates (compile with "cc -lgps qgps.c -o qgps")
3. PHP code to install on web server
4. SQL to create database and tables used to store GPS data