# OmniSTAR differential correction service

OmniSTAR® is a wide‑area differential GPS service provider.

OmniSTAR correction signals are available worldwide, but are only supported by an OmniSTAR‑capable GNSS receiver and a subscription must be bought from OmniSTAR to receive a subscription authorization.

OmniSTAR signals provide real‑time, differentially corrected positions without the need for a radio link. You can use OmniSTAR for:

- real-time differential surveys
- fallback in an RTK survey when the ground‑based radio link is down

Subscription levels for OmniSTAR corrections include:

- OmniSTAR HP, G2 and XP – all three are displayed in Trimble Access as OmniSTAR HP
- OmniSTAR VBS – displayed in Trimble Access as OmniSTAR VBS

The OmniSTAR subscription expiry date is displayed on the OmniSTAR initialization screen or from the Instrument / Receiver settings screen.

In an OmniSTAR survey, QC1 quality control information is available, while QC2 and QC3 are not available.

To track OmniSTAR satellites, start a survey using a style that specifies OmniSTAR as the Satellite Differential service. Once you end that survey, subsequent surveys will track OmniSTAR satellites until you start a new survey with a style that does not specify OmniSTAR for the Satellite differential.

To start a survey, see To start an OmniSTAR survey.