Understanding NDGPS or National Differential Global Positioning System

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What is NDGPS?

NDGPS stands for Nationwide Differential Global Positioning System. NDGPS, which is a radio-based navigation system, is used in tandem with global positioning systems to provide people on the road with accurate road and travel conditions. The US Department of Transport is responsible for the implementation of NDGPS.

Why is NDGPS implemented?

The main goal of implementing this technology is to reduce road congestion and to keep the roads safe. With thousands of Americans dying every year due to automobile crashes, the US Department of Transport took steps to decrease this number. A lot of fatal road accidents are single-driver accidents, which means the driver took a wrong turn or was not aware of the conditions of the road they were on. The US Department of Transport hopes to use NDGPS to reduce the number of accidents and fatalities on the road by providing drivers accurate information on their location relative to the highway infrastructure. This information includes traffic conditions and other relevant road infrastructure data.

With the information provided by the GIS (Geographic Information System) for NDGPS use, drivers can be alerted to road congestion, road accidents and other possible hot spots. This will allow drivers to maneuver around congested areas safely with great accuracy. Thanks to NDGPS, drivers can now be safer and they can also save time in traveling.


Combined with GPS, NDGPS can provide more accurate data to drivers compared to using GPS alone. The accuracy of GPS ranges from 4 meters to 20 meters. With the help of NDGPS, that accuracy range is improved to 1-3 meters. NDGPS compares its data with GPS data and then it eliminates inaccuracies to give the driver a far superior accurate location information. NDGPS owes its accuracy to the fact that it uses a low frequency process for radio broadcasts. This type of low radio frequency is the most accurate in terms of long range transmission that may involve obstructions and radio interference.

Other Applications of NDGPS

Transportation departments of states all across the US are using NDGPS to map out the infrastructure of their highways and roads. In a matter of hours, a complete road grid inventory for a state can be produced and made accessible. It is a far cry from the several days of waiting time for the same kind of road grid inventory using traditional road mapping methods. Police departments in several states use NDGPS to mark road accident locations, congested areas and other hot spots on road grids. Environmentalists use NDGPS to identify areas that need protection to preserve endangered animals or areas that are potential habitats for different kinds of animals. Emergency response units use NDGPS to accurately identify hazardous environments and dangerous terrain to aid them in rescue missions or accident prevention measures.


The next step in the evolution of NDGPS is HA-NDGPS or High Accuracy National Differential Global Positioning System. Currently under development, this system aims to improve the accuracy of NDPGS, which is 1-3 meters to 10-15 centimeters. Performance and integrity of the coverage area are also going to be improved.

You may also want to read related topics such as RINEX, SBAS and TTFF.