A. Ninety-five percent of the time, GPS accuracy is often within or 9 to 10 feet. In worst- case conditions, however, accuracy can degrade to 25 to 26 feet. To ensure the most accuracy, your GPS antenna should have a clear, unblocked view of the sky. Blockage can limit satellite-signal reception, which diminishes accuracy. Check your GPS's status screen. It is a good indicator of satellite reception, signal strength and positional accuracy. The more satellites, the more precise your position fix. Create benchmarks, such as your position in your slip, at known navigation aids and familiar landmarks, to confirm your GPS is experiencing normal accuracy. Also, keep your GPS software and cartography up to date. Installing an external antenna, rather than relying on an internal one, is one of the easiest means to increase GPS accuracy.