Detailed Justification for the Nationwide Differential Global Positioning System (NDGPS) Program

Detailed Justification for the Nationwide Differential Global Positioning System (NDGPS) Program

What Do I Need To Know Before Reading This Justification?

The Nationwide Differential Global Positioning System (NDGPS) Program provides national, real-time accurate dynamic positioning and navigation information at one-to-three meters for surface transportation users.  NDGPS receives substantial routine use by highway, transit and rail sectors in operations, maintenance, planning, construction, quality assurance and asset management. Multiple other Federal agencies, state and local governments and private sector users in many economic sectors meet mission requirements in precision agriculture, surveying and mapping, GIS, environmental and natural resource management, and severe weather forecasting using the NDGPS service.

  • The funding requested in the FY 2012 President's Budget aims to address system technical, cost and performance threats caused by deferred maintenance, by:
    • Establishing a robust operations and maintenance (O&M) floor for reliable system availability to users; and
    • Initiating a recapitalization of system equipment to bring the DOT sites up to current Coast Guard operational standards. The FY 2012 funding request provides 100 percent of routine O&M needs and 50 percent of recapitalization costs.
  • NDGPS is funded through DOT to support surface transportation users. However, it is recognized that multiple Federal agencies/sub-agencies, state and local governments, and private sector users in many economic sectors leverage DOT's investment in NDGPS to meet their requirements.
  • Although NDGPS is funded through RITA, NDGPS is an operational nationwide positioning and navigation utility, not a research and technology program. It provides an infrastructure to support limited DOT R&D projects.

What Is The Request And What Will We Get For The Funds?

FY 2012 Nationwide Differential Global Positioning System (NDGPS)
Budget Request

Program Activity FY 2010 Actual FY 2012 Request Change FY 2010-2012
Nationwide DGPS 4,600 7,600 3,000
Total $4,600 $ 7,600 $ 3,000

The request is to enable:

  • NDGPS to maintain system availability at the 29 inland segment sites at 98.5% or better;
  • Reduced risk of failure by bringing inland segment stations up to Coast Guard standards.
Key Actions Key Outputs Key Outcomes
  • Exercise robust O&M protocols
  • Reduce maintenance backlog
  • Initiate equipment recapitalization effort
  • Maintain system availability at ≥ 98.5%
  • Reduce programmatic risk (technical, cost, performance)
  • Eliminate outdated equipment
  • Technology providers and users can make investments based on improved system reliability/reduced risks
  • Enables ability to troubleshoot issues remotely; outyear O&M cost growth reduced

What Is This Program?

Strategic Goals: The Nationwide Differential Global Positioning System (NDGPS) supports the safety and environmental sustainability strategic goals.

Purpose/Beneficiaries: Provides a national service that delivers real-time, accurate dynamic positioning and navigation information at one-to-three meters (and often submeter) for civil transportation applications. NDGPS accomplishes this goal through local broadcast of accurate GPS position corrections ( The Coast Guard operates NDGPS as a nationwide DGPS utility coordinated with the Maritime DGPS and inland waterways sites ( DOT provides NDGPS for surface transportation applications and there is significant public and private sector reliance on NDGPS for precision agriculture, environmental management, natural resource management, surveying and mapping, severe weather forecasting and other applications.

Partners: U.S. Coast Guard and other federal, state and local agencies.

Description: NDGPS provides support infrastructure for several DOT research projects, and opportunities for future cross-modal surface transportation safety, security, efficiency and emergency response services.

Why Is This Particular Program Necessary?

NDGPS augments GPS by providing increased accuracy and integrity for transportation applications. ( The NDGPS service provides reliable GPS to meet the growing requirements of surface transportation users.

In addition to providing a real-time broadcast of corrections, NDGPS provides a robust operational backbone to the DOC's CORS application ( for post-processing survey applications and Web-enabled location solutions, the National Weather Service's Forecast Systems Laboratory for short-term severe weather and precipitation forecasts, space weather forecasts, and for plate tectonic monitoring.

The equipment recapitalization will bring the inland NDGPS segment to the Coast Guard operational standard, enabling remote troubleshooting and reducing outyear O&M cost growth. Coast Guard completed maritime DGPS recapitalization in 2009, and has realized significant operational efficiencies. Inland NDGPS equipment beyond serviceable life is being maintained at high risk of failure and at increased expense by purchasing/stocking/rebuilding expensive parts.

NDGPS availability and accuracy is leveraged by multiple other Federal agencies to meet their requirements in surveying and mapping, precision agriculture, environmental and natural resources management; historical resources management; and emergency response. A new use in FY 2011 was integration of the NDGPS in the Department of Homeland Security's (DHS) GPS Interference Detection and Monitoring (IDM) system for identifying GPS interference and service interruptions.

Without this funding, hundreds of thousands of users across multiple economic sectors would be unable to receive the accurate positioning information on which they depend daily for routine operations, and the growing location-based services market would be negatively impacted, as documented in NDGPS Assessment: Final Report.

How Do You Know The Program Works?

Effective: DOT's NDGPS Assessment: Final Report documents hundreds of thousands of routine NDGPS users across multiple sectors, and a minimum system return on investment (ROI) for the Federal-Aid Highway Program of 40:1. ROI for other Federal agencies, state and local governments and private sector could not be calculated, but includes a significantly larger user base.

Research: Ongoing feedback received from the user community through the Civil GPS Service Interface Committee (CGSIC;, the worldwide forum for effective interaction between all civil GPS users, supports the continued need for the NDGPS service, and to the expectation of expanded future uses in transportation and other economic sectors, especially if accuracy can be improved.

Research: Recognizing the cross-sector interest in a robust, higher-accuracy augmentation, the U.S. Department of Agriculture is conducting a study suggesting expanded NDGPS applications, Evaluating the Potential for New Civil User Services That Could Be Provided From DGPS Sites.

Efficient: New receiver manufacturers are producing commercial DGPS-based products for the market, demonstrating both market/user demand and a recognition of system reliability, and increasing cross-sector interest in a higher-accuracy augmentation.

Why Do We Want/Need To Fund The Program At The Requested Level?

Funding options: The requested level of funding is needed to support robust O&M to maintain system reliability and availability commitments to the Federal, state and local transportation user communities; and to reduce program technical and cost risk by continuing to replace aged equipment that is at risk of failure.

History/Outyear Needs: FY 2010 $4.6M; FY 2012 $7.6M.