Differential GNSS (DGNSS)

DGNSS improves navigation accuracy by calibrating correlated range errors using measurements from a reference station at a pre-surveyed location. However, tracking errors, multipath effects, and NLOS reception errors remain uncorrected since they are uncorrelated between locations.

How DGNSS Works

A reference station transmits correction data via a data link to a nearby rover (within 5–10 km).
Key steps:
1. Baseline computation: Differences in observations between the reference and rover are used to calculate the vector between them.
2. Rover position: Adding the baseline vector to the reference station's known coordinates gives the rover's position.

Local and Regional DGNSS

Local Area DGNSS (LADGNSS)

Corrections from a single reference station are transmitted to users (rovers) within the station's range.
User computes relative clock offsets and corrects errors for the selected satellites.

Regional Area DGNSS (RADGNSS)

Enhances LADGNSS by using corrections from multiple reference stations.
Increases accuracy for wider regional coverage.

Wide Area DGNSS (WADGNSS)

Provides meter-level accuracy over large areas (e.g., continents or countries).
Uses satellite broadcasts for corrections instead of terrestrial or network-based transmissions.
Corrections process:
- Reference stations send pseudo-range and ionosphere delay measurements to a Master Control Station (MCS).
- The MCS computes corrections for satellite ephemeris, clock parameters, and ionosphere data, then broadcasts them via satellites.

Relative GNSS (RGNSS)

Focuses on accurate positioning relative to a reference station rather than absolute accuracy relative to Earth.
Computes the baseline vector by differencing pseudo-range measurements from the reference and rover.