TO:         All Dealers
FROM:   Furuno
RE:          USCG Navigation Center:
                Facts Regarding DGPS vs WAAS                           

  May 22,2001                   14.01


The U.S. Coast Guard Navigation Center recently posted an informative WAAS vs. DGPS Question and Answer Report on their newly re-designed website.  This Q&A report provides many interesting facts regarding WAAS and provided unbiased facts about how WAAS and DGPS have been optimized for different purposes.

 The USCG Navigation Center website is an invaluable source of information for anyone involved in the Marine Electronics Industry.  Here is the URL link to the site:

 The WAAS vs. DGPS Q&A Report is titled “WAAS, DGPS and the Mariner’s Toolkit”.  The report is currently located on the site’s home page. In the future, it will be found under the May 2001 News on the USCG Navcenter website.

 Here are some basic facts extracted from the report: 

  • DGPS is more accurate than WAAS when used in coastal waters (<100NM from a DGPS Tx Site).
  • WAAS is NOT fully operational and is currently operating in an indefinite testing phase.  This testing phase could last at least several years during which unannounced interruptions and accuracy anomalies occur at any time.
  • WAAS ENABLED GPS RECEIVERS MUST NEVER BE USED by any Safety Of Life At Sea (SOLAS) Regulated Vessel for harbor entrance and approach phases of navigation.
  • DGPS is fully operational and meets all standards for SOLAS vessels.
  • DGPS should be used in any navigational situation on any vessel equipped with a Differential GPS Receiver.
  • WAAS is not optimized for maritime and “Surface of the Earth” installations.  It is a “Line-of-Site system designed primarily for aviation purposes.
  • The WAAS Signal can be easily blocked in any maritime installation, and CANNOT be received in certain northern latitudes because of “Ground Clutter” interference.  DGPS cannot be blocked and has no limitation with respect to this issue.
  • WAAS is NOT an international standard and can only be received in the North America Aviation Coverage Area.  DGPS is an international standard and can be utilized by mariners in at least 40 countries throughout the world.
  • DGPS coverage is growing in the US.  The USCG DGPS System has long term funding and will never be replaced by WAAS.



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