What principle does National Differential GPS (NDGPS) utilize for accuracy?

National Differential GPS (NDGPS) improves the accuracy of GPS signals by utilizing ground-based DGPS locations. This system involves a network of reference stations that compare the GPS signals they receive against known locations. By doing this, they can calculate the errors associated with the GPS signals. These errors are then broadcast to nearby GPS receivers, which can apply the corrections to their own positional data, leading to significantly enhanced accuracy on the ground.

The concept relies heavily on terrestrial infrastructure to correct satellite positioning inaccuracies caused by atmospheric conditions, multipath effects, or satellite ephemeris errors. Overall, ground-based reference stations play a crucial role in ensuring that the corrections provided are timely and precise, which ultimately enhances the positioning capabilities of standard GPS systems.