OmniSTAR Differential Correction Service
OmniSTAR provides space-based GNSS correction services that can improve the accuracy of a GNSS receiver for precise positioning applications. Currently, there are four levels of OmniSTAR service:
- OminSTAR VBS offering sub-meter positioning
- OmniSTAR XP delivering better than 20 centimeter accuracy
- OmniSTAR HP delivering greater than 10 centimeter accuracy
- OmniSTAR G2 service combines GPS plus GLONASS based corrections to provide decimeter level positioning
OmniSTAR is a wide-area differential GPS service, using satellite broadcast techniques. For the sub-meter service, data from many widely-spaced Reference Stations is used in a proprietary multi-site solution over most land areas worldwide. The high-accuracy HP solution uses more sophisticated data from these reference sites and XP uses satellite orbit and clock correction data which is independent of reference site location.
Trimble acquired certain assets related to the OmniSTAR Global Navigation Satellite System (GNSS) signal corrections business from Fugro N.V. in 2011.
OmniSTAR-HP service is the most accurate solution available. It is a L1/L2 solution requiring a dual frequency receiver. Data from OmniSTARs network of reference sites is utilized together with atmospheric corrections. Carrier phase measurement is used to maximize accuracy. OmniSTAR HP will usually have a 2-sigma (95%) horizontal error of about 6 centimeters and a 99% horizontal error of less than 10 centimeters. It is particularly useful for Agricultural Machine guidance and many surveying tasks. It operates in real time and without the need for local Base Stations or telemetry links. OmniSTAR HP is a true advance in the use of GPS for on-the-go precise positioning.
OmniSTAR-XP is a worldwide dual frequency high accuracy solution. It is a L1/L2 solution requiring a dual requency receiver. Orbit and Clock correction data is used together with atmospheric corrections derived from the dual frequency data. By utilizing carrier phase measurement, very high accuracy can be achieved. OmniSTAR XP service provides short term accuracy of 1-2 inches and long term repeatability of better than 10 centimeters, 95%CEP. It is especially suited for Agricultural automatic steering systems. While it is slightly less accurate than OmniSTAR HP, it is available worldwide and its accuracy is a significant improvement over regional Differential Systems such as WAAS.
OmniSTAR-VBS is the foundational "sub-meter" level of service. It is an L1 only, code phase pseudo-range solution. Pseudo-range correction data from OmniSTARs regional reference sites is broadcast via satellite link to the user receiver. These data are used, together with atmospheric modeling and knowledge of the receivers location, to generate an internal RTCM SC104 correction specific to that location. This correction is then applied to the real time solution. A typical 24-hour sample of OmniSTAR VBS will show a 2-sigma (95%) of significantly less than 1 meter horizontal position error and the 3-sigma (99%) horizontal error will be close to 1 meter.
OmniSTAR-G2 represents the most recent advancement in OmniSTAR subscription service offerings. It is a worldwide dual frequency high-accuracy solution which uses Orbit and Clock correction data. OmniSTAR G2 includes GLONASS satellites and GLONASS correction data in the solution. The addition of GLONASS to the solution significantly increases the number of satellites available which is useful when faced with conditions that limit satellite visibility, such as terrain, vegetation or buildings. OmniSTAR G2 service provides short-term accuracy of 1-2 inches and long term repeatability of better than 10 centimerers, 95%CEP. It is especially suited for operations in areas where trees or buildings may block the view of the sky and in areas affected by scintillation during times of high sunspot activity.