NASA Home Page JPL Home Page Caltech Home Page
NASA - Jet Propulstion Laboratory vertical separator + View the NASA Portal
JPL Home JPL - Earth JPL - Solar System JPL - Stars and Galaxies JPL - Technology
Global Differential GPS System
About Us
System Description
- Overview
- Network
- Software
- References
Live Performance Monitoring
Customer Portal
Orbit & Clock Corrections

The GDGPS System provides 1 Hz corrections to the GNSS spacecraft position (X, Y, Z coordinates), and clock state in the broadcast ephemerides. Differential corrections are available for the following constellations: GPS, GLONASS, BeiDou, Galileo, and QZSS. They are globally and uniformly valid - just like the broadcast ephemerides.

Adding the corrections to the broadcast ephemerides gives the precise orbit and clock state of the spacecraft, typically accurate to better than 20 cm 3D RMS. In fact, we derive the orbit and clock corrections by subtracting the broadcast ephemeris from our precise real-time orbit and clock solution product.

The corrections for the GNSS satellites are available as in a variety of streaming data formats, including a compact JPL format, and the RTCM Space State Representation (SSR) format.

The correction message includes velocities of the orbital corrections, enabling the user to propagate the corrections into the future, and be resilient to short data outages.

Look at our live performance monitor to see real-time point-positioning carried out, utilizing our correction data stream.

The following table summarizes the key attributes of this product. It applies to all medium Earth altitude GNSS satellites. Geosynchronous, and inclined geosynchronous satellites (in the BeiDou and QZSS Systems) are somehwat worse.

< 20 cm 3D RMS
< 20 cm RMS (after de-biasing and de-trending)
< 10 cm RMS
Latency 4-6 seconds
Format Proprietary binary or RTCM SSR
60 seconds
1 second
Access mode UDP (recommended) or TCP

Real-time GNSS
Products & Services
Precise, Global, Reliable
- Embedded Autonomous Ephemeris Prediction (AEP) software
- Orbit & Clock Corrections
- Orbit & Clock States
- Broadcast Ephemeris & Almanac
- Complete 50 bps Navigation Message
- Global Ionospheric (TEC) Maps
- Raw Measurements
- Predicted Orbit & Clock States
- Integrity & Performance Monitoring
- Global Virtual Reference Network
- Assisted GNSS Data
- GLONASS corrections, orbit and clocks

- Automatic Precise Positioning Service
- Consulting
link to First Gov NASA logo