Proposals for The Future of NDGPS Rick Foote National Geodetic Survey, NOAA & National Coordination Office for Space-Based Positioning, Navigation, and Timing January 31, 2013

Positioning, Navigation, and Timing web site at

What is NDGPS? NAVCEN operates the Coast Guard Maritime Differential GPS (DGPS) Service and the developing Nationwide DGPS Service, consisting of one control center and 86 remote broadcast sites. The Service broadcasts correction signals on radiobeacon frequencies to improve the accuracy and integrity to GPS-derived positions. Typically, the positional error of a DGPS position is 1 to 3 meters. Source:

Current State of NDGPS

DOT – Plan for discussions spring through fall of 2013 Proposal from 2012 Federal Radionavigation Plan (Draft): Nationwide Differential GPS Section 5.2.4; pg “The Department of Homeland Security, in coordination with the Department of Transportation, is analyzing the future of the NDGPS beyond Fiscal Year (FY) Future decisions might include: decommissioning NDGPS as currently configured, maintaining NDGPS as currently configured, or developing alternate uses for the infrastructure. Contributing factors to these proposals are: 1) U.S. Coast Guard change in policy to allow aids to navigation (ATON) to be set with a GPS receiver using Receiver Autonomous Integrity Monitoring (RAIM); 2) lack of availability of consumer grade NDGPS receivers at retail outlets; 3) no carriage requirement on any vessel within U.S. territorial waters; 4) the U.S. Government turning off SA; 5) continuing GPS modernization and, 6) the Federal Railroad Administration determines that neither NDGPS, nor High Accuracy NDGPS, are required for successful implementation of Positive Train Control.

Recent Meeting highlights December 13: PNT Executive Steering Group 1.Similar ESG discussion five years ago recommended keeping NDGPS as-is 2.Due to budget cycles, change could not take place before FY 2016, and any change would be phased in over three years 3.Plan is not for decommissioning, but for discussions of the future of NDGPS 4.The National PNT Architecture guidance is to transition or divest unnecessarily redundant augmentation systems 5.Upcoming Federal Register Notice will lead to public hearings in 2013 to discuss the impact of the possible alternatives 6.NOAA could have some operational impact associated with decommissioning of NDGPS 7.DOI suggested that phasing out NDGPS should not be start until GPS signals are modernized 8.National, state, and local agencies should compile list of NDGPS users

Recent Meeting highlights January 23: DOT Pos/Nav Working Group 1.Presentation by USCG Office of Navigation Systems – CDR Harry Wilson and DOT – Research and Innovative Technology Administration (RITA) 2.ESG action item – “In cooperation with USCG and other Federal agencies, DOT Extended Pos/Nav WG shall assess potential NDGPS closure impacts” 3.Canada is also studying decommissioning of their sites 4.NDGPS will not work without GPS! 5.One site (Omaha) has already been approved for decommissioning in March, and 19 “caretaker” sites will not be constructed – no budget support 6.Oversight by Space-Based PNT EXCOM/ESG

Member agencies for PNT Executive Committee

HA-NDGPS The High Accuracy NDGPS (HA-NDGPS) research program goal is to develop an inexpensive technique to achieve navigation to better than 10 cm accuracy using existing infrastructure to the maximum extent possible. If added to the NDGPS, this upgrade is expected to provide 2 to 15 cm accuracy and a time-to-alarm of 1 s throughout the United States. This high- accuracy signal will enable a wide range of new applications that are not currently possible with today’s NDGPS signal. DOT is developing requirements supporting both high accuracy and integrity functions. While these are being developed, research is continuing. Source: 2012 FRP, Section (Draft)

NDGPS Costs From the Federal Highway Administration Report from NDGPS Assessment Final Report: The annual costs to maintain the NDGPS network in its current level of build-out is approximately $5 million (FY08 dollars, source USCG). (per Tim Smith – NPS, Jan 31, 2013 AM meeting - $15 million per year) The projected cost to complete deployment of the NDGPS network to 99% single coverage is approximately $6.0 million. A projected $3.45 million is needed for recapitalization to replace outdated equipment. The projected cost to complete deployment of the NDGPS network to Full Operational Capability is approximately $19 million. At full deployment, the estimated annual operating cost is $5.4 million (FY08 dollars, source USCG). The projected cost to decommission the NDGPS network is $30 million. (per Tim Smith – NPS, Jan 31, 2013 AM meeting - $18 million. Each site costs $100, ,000 to decommission) Source: Federal Highway Administration NDGPS Assessment Final Report:

Alternatives to NDGPS - WAAS For real-time applications, the primary alternatives to NDGPS are the Federal Aviation Administration’s Wide Area Augmentation System (WAAS) and commercial augmentation systems. In areas of clear sky coverage, these systems can provide equivalent performance to NDGPS. Many users are unaware of the differences in services. WAAS is used by many recreational users for simple navigation, whereas NDGPS users typically have requirements for accurate navigation and positioning in all environments including wilderness areas, areas with topographical influences, and areas of heavy terrain or foliage which present problems for line-of-sight augmentation systems. Source: Federal Highway Administration NDGPS Assessment Final Report:

Alternatives to NDGPS - RTK For many current NDGPS users and their applications, if 1-2 meter horizontal accuracy is required or if an integrity warning is required, the only viable alternative is more expensive equipment and specialized techniques such as high-accuracy survey equipment or Real-Time Kinematic (RTK) processes. Real-Time Kinematic equipment is times more expensive than an NDGPS receiver, and requires advanced training, longer setup time and may require post-processing of position data. Source: Federal Highway Administration NDGPS Assessment Final Report:

DOT Pos/Nav input needed What are your documented PNT requirements? Identify how NDGPS is used to meet these requirements How does possible decommissioning impact your program? Are there alternate systems you could use if NDGPS is scrapped? Please reply to by Feb. 28, 2013 to allow review before next Executive Steering Group meeting in March

Some NOAA usage of NDGPS Question: How are you currently using NDGPS? NOAA's Earth System Research Laboratory acquires NDGPS dual frequency carrier phase observations and meteorological observations from NOAA GPS Surface Observing System (GSOS) packages installed at virtually all NDGPS sites from NGS in near real time. We process these observations every 30-minutes to estimate the total zenith tropospheric signal delay, use these estimates to retrieve integrated total atmospheric water vapor, and provide this information to NOAA weather models, weather forecasters, and researchers in the U.S. and internationally. Question: How does possible decommissioning impact your program? NDGP GPS observations are highly reliable since the sites are maintained by the U.S. Coast Guard as Operational Commissioned systems. Often times, they are the only source of surface and upper-atmospheric moisture information available to NOAA leading up to and immediately following major disasters such as hurricanes including H. SANDY in 2012 and H. KATRINA in Question: Are there alternate systems you could use if NDGPS is scrapped? Yes, but data availability will be less reliable Other responses received from Office of Coast Survey – Hydrographic Services, and NGS Remote Sensing Division

Questions?