U.S. Coast Guard discontinues Differential GPS broadcast

The following is excerpted from a bulletin posted June 29 by the U.S. Coast Guard. The complete bulletin is available online.

On June 30, 2020 the Coast Guard switched off the last Differential Global Positioning System (DGPS) signals after more than 25 years of service.

With the improved accuracy and integrity of un-augmented GPS over the last several years, and with the introduction of the U.S. operated satellite-based augmentation system known as Wide Area Augmentation System (WAAS), the maritime community no longer has a mission requirement for DGPS. GPS now provides sufficient positional accuracy to meet international navigation requirements for harbor approaches and to position Federal Aids to Navigation (ATON).

The Global Positioning System is a U.S. government owned utility that is now ubiquitous, and provides users with free, highly accurate positioning, navigation, and timing (PNT) services. GPS technology can be found in cell phones and watches, shipping containers, and ATMs. It is essential for all forms of navigation, farming, surveying and construction, banking and the financial markets, and the power grid. In its earlier iterations the information GPS provided was not accurate enough for some applications, including the Coast Guard's positioning of marine aids to navigation. To solve this problem, in the late 1980s and early 1990s, the Coast Guard established the Maritime Differential GPS System to augment the existing GPS signal with accuracy corrections and integrity monitoring by broadcasting over Medium Frequency from terrestrial broadcast sites. The correction brought GPS position accuracy from several meters to less than one meter.