User:Michaelb1/Uscg navigation center

USCG Navigation Center

Technicians at the USCG's Navigation Center (NAVCEN) in Alexandria, Virginia monitor the broadcast signals from 86 remote Nationwide Differential Global Positioning System (DGPS) sites and evaluate the status of 115 Nationwide Automated Information System (NAIS) sites collecting vessel position data for critical ports throughout the United States. Other watchstanders track the reporting status of over 680 U.S. flagged vessels registered in the Long Range Identifi cation and Tracking (LRIT) program.

NAVCEN was created through the consolidation of several Coast Guard navigation programs under a single command. These programs included Long Range Aids to Navigation (LORAN), Omega Navigation system (Omega), and DGPS. As additional programs such as Nationwide Automated Identification System (NAIS), Long Range Identification and Tracking (LRIT), and Navigation Information Service (NIS) were developed and came online, they were also brought under the purview of NAVCEN.

LORAN and Omega were originally designed, tested, and implemented by the U.S. Department of Defense (DOD). Upon DOD request, the U.S. Coast Guard took over operations and maintenance for both systems. NAVCEN began as the Operational Commander for the international Omega radio-navigation program in 1971 and was originally known as the Omega Navigation System Operations Detail. Although the program originated in the United States, seventy-five percent of all Omega sites would eventually be located in foreign countries. As Omega expanded globally, so too did NAVCEN’s role. The Omega Navigation System Operations Detail later became known simply as Omega Navigation System Center (ONCEN), and it took responsibility for the day-to-day system operation of Omega in cooperation with foreign partners.

By the time ONCEN was established, the U.S. Coast Guard had already been managing the LORAN system for several years with multiple control stations throughout the United States. LORAN was established during World War II (WWII) under a secret program to provide accurate navigation capabilities at sea in any weather. Post WWII, the U.S. Coast Guard expanded and enhanced the LORAN system because of its obvious value to merchant and military users. LORAN-C would enter the scene in the 1970s and by 1974 the U.S Coast Guard operated and supported 45 stations worldwide. By the 1990s, the foreign based stations were turned over to their respective host governments, reducing the U.S. Coast Guard’s operational footprint to only North America. The operational monitoring of all LORAN stations would morph with ONCEN in the 1990s resulting in a centralized command for monitor and control of LORAN stations.

As LORAN and Omega continued to serve navigators throughout the nation and world, DOD’s Global Positioning System (GPS) services eventually became available to the public. GPS reached full operating capability in 1995, and with it came requirements for the U.S. Coast Guard to perform civil interface responsibilities and meet harbor/harbor approach positional accuracies. The U.S. Coast Guard would pave the road for high-accuracy positioning as it pioneered the DGPS technology. As the operational requirements for Omega, DGPS, and LORAN grew, the U.S. Coast Guard would centralize its control efforts in Alexandria, VA; and in 1995 the U.S. Coast Guard Navigation Center was commissioned. With the advent of more modern and accurate systems, the cost for operating Omega could no longer be justified; and in September of 1997, the Omega signals were terminated. NAVCEN would continue to monitor and operate LORAN for several years to support mariners needing precise positioning, and a backup to the GPS service. Then in January 2010, after approximately 68 years of operation, the Department of Homeland Security published a notice for discontinuation of LORAN; NAVCEN eventually terminated the signal in February 2010. Today, NAVCEN is the lead U.S. Coast Guard command for navigational systems management. Through innovation and continuous improvement, NAVCEN has become the primary source for maritime navigation and information services in and around the United States.

Located on the campus of the U.S. Coast Guard Telecommunications and Information Systems Command in Alexandria, VA, modern day NAVCEN is home to nearly 80 active duty military, civilian government employees, and contracted personnel. Its mission is to provide maritime navigation and information services that enhance the safety, security, and efficiency of U.S. waterways. These services include: providing nationwide GPS augmentation signals, tracking vessel movements for enhanced maritime domain awareness, publishing maritime advisories and related navigation information, managing the U.S. Coast Guard's electronic chart portfolio, and receiving and coordinating investigation of GPS outage reports.

At the heart of NAVCEN is the Maritime Information Operation Center (MIOC). The MIOC is staffed 24 hours a day, 7 days a week, 365 days a year to provide real-time monitoring and control of these navigation, positioning, and Marine Domain Awareness (MDA) systems:

Nationwide DGPS: NAVCEN operates and maintains the Nationwide DGPS service providing 99.7% signal availability to U.S. coastal, inland, and inland river areas. DGPS is an augmentation to GPS position which increases the positional accuracy to approximately one to three meters. Position corrections to GPS are generated and broadcast to the public, free of user fees, using a network of 86 land-based reference stations. The system also provides integrity alarms for GPS and DGPS, alerting NAVCEN watchstanders and system users to out-of-tolerance conditions within 10 seconds of detection. The Nationwide DGPS system provides DGPS coverage to the coastal areas of the lower 48 states, major inland rivers, Great Lakes, Gulf of Alaska, Hawaii and Puerto Rico, and 92% of the inland areas of the continental United States. DGPS is used for accurate placement of navigational aids throughout the U.S. coastal waterways. In addition, the system is used for efficient land surveying, improved weather forecasting, plate tectonic monitoring, precise application of fertilizers and pesticides for agriculture, and applications that enhance public safety, commerce, and scientific research. Every Nationwide DGPS site feeds data into the National Geodetic Survey Continuous Operating Reference Station (CORS) database for post-processing applications to achieve centimeter level positional accuracy.

GPS Civilian Interface: NAVCEN functions as a liaison between civilian users and the U.S. Department of Defense on GPS operations and management. To achieve this, NAVCEN coordinates and manages the Civil GPS Service Interface Committee (CGSIC) as part of the U.S. Government’s program to respond to the needs of civilian GPS users. The CGSIC is the recognized worldwide forum for interaction between civil GPS users and the U.S. GPS authorities. CGSIC is comprised of U.S. and international members from government and industry user groups. Four subcommittees focus on specific issues: International Information; Survey, Mapping and Geo-Sciences; Timing; and U.S. States and Localities. The subcommittees meet at various locations and times depending on the needs of their members. The CGSIC meets annually in a plenary session and is open to anyone interested in civil GPS issues. Information from CGSIC members and meetings is provided to U.S. GPS authorities for consideration in policy development and service operation.

GPS Interference Detection and Mitigation (IDM): The critical infrastructure and commercial industry of the U.S. has become increasingly reliant on the Position, Navigation, and Timing (PNT) services from the Global Positioning System (GPS). NAVCEN plays an important role in the U.S. Department of Homeland Security’s GPS Interference Detection and Mitigation plan. NAVCEN accepts GPS outage reports from any user, responds to the user inquiries within 1-2 days, and facilitates interagency resolution activities.

Nationwide Automated Identification System (NAIS): NAVCEN continues to advance its e-Tracking capabilities with the ongoing installation and advancement of the Nationwide Automated Identification System. NAIS is the U.S. Coast Guard’s implementation of AIS, an international standard for ship-to-ship, ship-to-shore, and shore-to-ship communication for identification and navigational safety information. Through NAIS, ships provide information about their position, speed, course, destination, cargoes, and other data of critical interest for maritime safety and security. NAIS uses this information for port security and management. NAIS continues to grow and is expected to be capable of providing coastal transmit capability out to twenty-four nautical miles and receive capabilities from two-thousand nautical miles offshore by 2014.

Long Range Identification and Tracking (LRIT) Business Helpdesk: The LRIT system allows for worldwide tracking via INMARSAT-C of U.S. flagged vessels over 300 gross tons (SOLAS class vessels) and certain foreign-flagged vessels. The U.S. maintains one of many National Data Centers (NDCs) around the world; all of which share information via the International Data Exchange. Such tracking ability increases maritime domain awareness and enables more efficient search and rescue response. NAVCEN serves as the civil interface for LRIT to the national maritime community and operates the only LRIT helpdesk in the United States.

Navigation Information Service (NIS): The NIS is a 24x7 live watch that provides professional customer service for reliable PNT (GPS, NDGPS), eTracking (NAIS, LRIT), and eNAV information to users worldwide. Additionally, NIS gathers, processes, and disseminates information related to system outages and other problems related to navigational safety through: Broadcast Notice to Mariners (BNM), Local Notice to Mariners (LNM), and Notice Advisory to NAVSTAR Users (NANU). This information is provided to system users via web downloads, e-mail list services, and U.S. Coast Guard message traffic.

The members of the MIOC watch work to keep these navigation, positioning, and MDA systems operating efficiently. At the other end of the building from the MIOC, NAVCEN’s Systems Support division manages technical and lifecycle issues for DGPS, GPS, and NAIS. These dedicated teams provide in-depth analysis of each system to ensure system performance meets published specifications and user requirements. They work closely with program managers, maintenance personnel, and interagency partners to enforce maintenance procedures and continue system modernization and standardization efforts.

Finally, NAVCEN is home to the Electronic Navigation and Charting Branch, commonly referred to as “Charting.” Charting distributes, updates, and maintains all standard electronic chart portfolios for U.S. Coast Guard cutters. They are responsible for creating and publishing the U.S. Light List, which includes weekly Summary of Correction notices and monthly revisions to the electronic version of each volume. Additionally, Charting ensures the public distribution of weekly Local Notice to Mariners from all nine U.S. Coast Guard Districts, which provide updates to the U.S. Light Lists, Coast Pilots, and navigation safety information.

A subset of Charting oversees one of the most important systems to manage Aids-To-Navigation (ATON) in the U.S.  The Integrated Aids-to-Navigation Information System (I-ATONIS) enables the management of all information for tracking visual ATON (buoys, beacons, lighthouses, etc.). Charting uses I-ATONIS for ATON asset tracking, budget modeling, maritime information reports, asset management, work scheduling, and other programmatic oversight functions.

link to DGPS wikipedia page http://en.wikipedia.org/wiki/Differential_GPS