Trackaroo Trackmaster

Three factors can affect the performance of your internal device/phone GPS:

1. Device Manufacturer Quality
   The accuracy of the internal device GPS can vary by manufacturer. For the most part, many of the latest phones have good GPS units that will be fine for most track days. A web search will usually turn up any serious GPS problems with your device.
2. Mounting
   Try not to mount your device so that the GPS signal is obstructed. This will degrade your GPS performance. You want to stay away from metal and be careful of stowing your device inside anything metal. The best mounting is to have the device with a clear view of the sky. This is usually near the windshield on cars.
3. Course Layout
   You may see insufficient data resolution with fast, tight course layouts like you find with karting or autocross. Most device GPS units have 1 Hz update rates (once a second). Trackmaster interpolates data, so it can do a pretty good job of compensating for the lack of resolution. External bluetooth GPS units can provide higher 5 Hz (5 times a second) and 10 Hz (10 times a second) update rates for better resolution.

If you find that your device GPS isn't performing, then go with an external bluetooth GPS. These units are inexpensive. They are very accurate, provide higher data resolution, and also provide flexible mounting solutions. Since you are not using the device GPS, you can store your device somewhere safe and place the external bluetooth GPS in the precarious mounting location instead.

Jeff