nga's support for positioning and navigationweb.stanford.edu/group/scpnt/pnt/pnt07...clocks to...

Know the Earth…Show the Way

NATIONAL GEOSPATIAL-INTELLIGENCE AGENCY

NGA’s Support for Positioningand Navigation

PNT Symposium6 November 2007

Barbara Wiley

Approved for Public Release NGA Case # 08-053


Know the Earth…Show the Way2

What is NGA and What Do We Do?National Geospatial-Intelligence Agency (NGA) is aNational Intelligence and Combat Support Agency

Definition:

“The exploitation and analysis ofimagery and geospatial

information to describe, assess,and visually depict physicalfeatures and geographically

referenced activities on the Earth.GEOINT consists of imagery,

imagery intelligence, andgeospatial information.”

GEOINT

ImageryIntelligenceImagery Geospatial

Information

Production Facility in Country XMain Vehicle Production

Administration Building

Production Building

Storage Buildings

Post-Flood July 200x

Mission:

Provide Timely, Relevant, andAccurate GEOINT in support of

National Security




Layers in the National System of Geospatial-Intelligence (NSG) define Positioning and Navigation

Know the Earth, Show the Way

Maps

Charts

Reference Frame (WGS 84)

Precise Positioning

Safety of Navigation

Digital Terrain Elevation Data

Digital Point PositioningDatabase




EQUATOR

Z

YX

0,0,0

PrimeMeridian

World Geodetic System 1984

●Reference Frame

●Datum Transformations

●Earth Gravity Models

●Global Vertical Datum

●World Magnetic Model

●Elevations

●Map/Charts

Ensure Scientific Integrity

Ensure Interoperability with other global systems




NGA’s GPS Mission

• 30+ years of satellite tracking• Precise orbits needed to produce precise

positions• From the Master Positioning, Navigation and

Timing Plan:– NGA is responsible for:

• Services to support DoD navigation systems• Maintenance of GPS fixed site operations• Generation and distribution of GPS precise ephemerides




GPS Operations and NGA– NGA GPS observations

• Directly improve GPS Broadcast Accuracy• Directly improve GPS Integrity Monitoring

– NGA GPS Precise Ephemeris• DoD Standard• Quality control for GPS operations

– Earth Orientation (from USNO)• Geodetic tie for GPS Earth-fixed to Inertial

Frame




GPS Monitor Station Network• GPS Wing designs and acquires the GPS space systems• USAF operates and maintains the GPS constellation• NGA provides trusted data and analysis to USAF on GPS

satellites referenced to WGS 84




NGA is the authoritative source for precise GPS ephemeris

NGA Precise Ephemeris for GPS is DoD Truth- Precise determination of where the satellites were- Precise GPS clock solutions- Used for precise positioning and system analysis




Future GPS Products

– Estimation and Prediction of Orbits andClocks to High Accuracy (EPOCHA)

• Near Real-Time, automated network distribution oforbital states to multiple customers

• Initially every 15 minutes• Goal is every 30 seconds• IOC is Summer 2009




INS

NavigationSolution

Internal toWeaponSystem 1

12

3

3

GPS

External toWeaponSystem 2

Gravity Data

Internal toWeaponSystem 3

Inertial Navigation SystemsGPS + INS + gravity = A more robust system




Inertial Navigation SystemsGPS + INS + gravity = A more robust system




Safety of Navigation





Know the Earth…Show the Way

nga's support for positioning and navigationweb.stanford.edu/group/scpnt/pnt/pnt07...clocks to...

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