Introduction
Standard RTK uses one base station. But what if you're halfway between two bases? Which corrections do you use? VRS solves this by creating a virtual base station exactly where you need it.
What Is VRS?
Virtual Reference Station is a technique used in network RTK. Instead of sending corrections from a single physical base station, the network creates a virtual base station at your approximate location.
From your rover's perspective, it's getting corrections from a base station right next to you, even though that base station doesn't physically exist.
Why VRS?
The problem with single-base RTK:
- Accuracy degrades with distance from base
- Different errors dominate at different distances
- No single base is optimal for all rovers
The VRS solution:
- Network of permanent stations (CORS)
- Central processor models errors across the whole area
- Creates customized corrections for each rover's location
- Every rover gets "local" accuracy
How VRS Works
- Rover sends its approximate position to the network (NMEA GGA string)
- Network processor analyzes data from all nearby physical stations
- Processor models ionospheric delay, tropospheric delay, orbit errors at rover location
- Processor generates synthetic correction data for a "virtual" base station at the rover's location
- Rover receives VRS corrections, applies them as if from a local base
- Rover achieves centimeter accuracy
VRS vs. Single-Base RTK
| Aspect | Single-Base RTK | VRS Network RTK |
|---|---|---|
| Baseline length | 10–30 km max | Up to 70 km from nearest physical base |
| Accuracy | Degrades with distance | Consistent across network |
| Setup | Need your own base | Just connect to network |
| Reliability | Single point of failure | Redundant network |
VRS Accuracy
| Distance from Nearest Physical Base | Typical Accuracy |
|---|---|
| <20 km | 1–2 cm |
| 20–40 km | 2–3 cm |
| 40–70 km | 3–5 cm |
| >70 km | Degrades rapidly |
Advantages and Disadvantages
Advantages
- No base station setup required
- Consistent accuracy across area
- Works immediately upon connection
- Redundant and reliable
- Ideal for large areas
Disadvantages
- Requires cellular coverage
- Subscription cost
- Latency depends on cellular network
- Not available everywhere
Vital Points
- VRS creates a virtual base station at your location
- Uses network of physical CORS stations to model errors
- Consistent accuracy across entire network
- No base station setup required, just connect
- Ideal for surveying, construction, agriculture
- Requires cellular coverage and subscription