How accurate is the Global Positioning System?
The U.S. Government is committed to providing GPS to the civilian community at the performance levels specified in the SPS Performance Standard. For example, the GPS signal in space will provide a “worst case” pseudorange accuracy of 7.8 meters at a 95% confidence level. The actual accuracy end users can expect depends on factors outside the government’s control, including atmospheric effects and receiver quality. Real-world data show that some high-quality GPS SPS receivers currently attain better than 3 meter horizontal position accuracy. Higher accuracy is available today by using GPS in combination with various augmentation systems. These enable real-time positioning to within a few centimeters, and post-processed positioning to within millimeters. The U.S. Government is committed to modernizing the GPS constellation to enable higher civilian accuracy without augmentations. The first of many next-generation GPS satellites was fielded in 2005.
