Orbit and Clock States
The precise real-time GNSS orbit and clock states are the core products of the Global Differential GPS (GDGPS) System, from which many other by-products and services are derived. We ensure that these are the most accurate real-time representation of the GNSS satellites state by employing the large real-time tracking network with nearly 250 global sites, and highly sophisticated and complete GNSS modeling and orbit determination software.
Below is a summary of the key attributes of these product. These typically apply to medium Earth altitude satellites. Geosynchronous, and inclined geosynchronous satellites (in the BeiDou and QZSS Systems) fare somewhat worse.
Product Specifications
| Attribute | Performance |
|---|---|
| Accuracy Orbits Clocks URE |
< 20 cm 3D RMS < 20 cm RMS (after de-biasing) < 10 cm RMS |
| Latency | 1 minute |
| Format | SP3c, RTGx (pos_goa, TDP), GDGPS streams |
| Frequency Orbits Clocks |
1 minute 1 Hz |
| Access mode | sFTP |
Quality Assessment
The GDGPS orbits are typically accurate to better than 20 cm 3D RMS, and the clocks are accurate to better than 20 cm RMS. Figure 1 below is updated daily to provide an independent assessment of the quality of the GPS orbit solution by comparing it with the JPL precise daily solutions, which are accurate to a few centimeters.
Figure 2 below shows the accuracy of the GPS clock solution for the past 14 days by comparing with JPL precise clock solution which is also accurate to a few centimeters. This figure is also updated daily.
Figure 3 below shows the User Range Error (URE), which is the effective combined accuracy of the orbit and clock solutions, for the past 14 days by comparing with the JPL GPS precise orbit and clock solutions. This figure is also updated daily.
The orbit and clock products are provided as ASCII files in various formats, including the industry standard SP3c, and internal RTGx formats. The files are available through secure FTP from our redundant servers. The files are available either as 1 minute 'chunks', or as 24-48 hour files, containing the real time solutions over the last 24 to 48 hours. The orbit and clock states are provided every 1 minute. For lower latency (seconds) and higher frequency (1 Hz) products see the Orbit and Clock Corrections product.
We'll be happy to customize this product for your needs.