GPS Unit

A global positioning system was the best solution for determining the location of the balloon and ground team not only because of convenience, but also because the size of a hand held unit is extremely small.  The GPS unit we decided to use for both the balloon and chase vehicle is the handheld Magellan SporTrak Pro.  The SporTrak Pro was chosen because it not only uses the 12 GPS satellites it also takes advantage of the U.S. Wide Area Augmentation System (WAAS), which makes it accurate to within 3 meters.  The SporTrak can also output NMEA sentences through a standard RS-232 serial cable, which allows the SporTrak to communicate with the amateur radio equipment.  The Magellan only requires two AA batteries for power, which will last for 12 hours, so building a power supply was not a concern.  Finally, we determined that stripping the plastic casing off would not be advantageous in the long run.  We determined that the added stability and protection received from leaving the casing on was worth the added weight.