Nationwide Differential Global
Positioning System (NDGPS)
To ensure greater accuracy and improved integrity, the US
Department of Transportation is deploying the Nationwide Differential Global
Positioning System (NDGPS) service.
This service uses ground reference stations to determine the
differential between the GPS solution and the true solution. This differential is then broadcast on a low
frequency carrier for users to access, free of direct user charge.
NDGPS provides accurate dynamic navigation information to
travelers with 1- to 2- meter accuracy (and possibly better in the future).
This will enable improved collision notification systems, cooperative
vehicle-highway collision avoidance systems, and more accurate in-vehicle route
guidance systems. When used in a static
mode, NDGPS offers a .1 to 1 meter service.
Figure 1. NDGPS Navigation Service
A proposed improvement to the NDGPS service, High Accuracy
NDGPS (HA-NDGPS) offers improved performance not only in accuracy, but in
reliability.
