RTK setups overview
RTK (Real-Time Kinematic) is a satellite positioning technique that improves GNSS receiver accuracy from a few meters to a few centimeters in real time.
RTK works by using two receivers:
- a stationary base station
- a moving rover
The base station is placed at a known location and continuously receives satellite signals. It then sends its satellite observations and position data to the rover. Since both receivers observe the same satellites under nearly identical conditions, the rover can compensate for atmospheric and satellite-related errors and calculate its position with centimeter-level accuracy in real time.
To learn more about RTK positioning, check out our blog article:
Learn how RTK works and how it provides centimeter-level positioning.
RTK setups
Reach receivers support several RTK setups depending on your fleet, internet availability, environmental conditions, and project requirements. Learn more about possible setups from the table below:
| Workflow | How it works | Internet required | Local base required | Best for | Third-party compatibility |
|---|---|---|---|---|---|
| LoRa | Base and rover communicate over Emlid's LoRa radio | No | Yes | Open areas without cellular coverage | Emlid receivers only |
| UHF | Base and rover communicate over UHF radio using Trimtalk 450S protocol | No | Yes | Dense vegetation or urban environments and mixed-fleet setups | UHF-compatible receivers supporting Trimtalk 450S protocol |
| Emlid Caster | Base and rover communicate over the free Emlid Caster service via the internet | Yes | Yes | Multi-rover sites with need for control over base | Any NTRIP-compatible receiver |
| RTK network (NTRIP) | Rover connects to a corrections network provider over the internet | Yes | No | Working without a local base station in urban and semi-urban areas with good cellular coverage | Not relevant |
RTK setup basics
Before starting surveying in RTK, you need to consider the following:
Satellite visibility
For RTK, both the base and rover need a clear view of the sky. Each receiver tracks satellites across multiple constellations. The more satellites visible simultaneously, the stronger and more stable the solution. Obstructions above 15 degrees of elevation, such as buildings, trees, and heavy canopy, block signals and reduce usable satellite count.
Communication link requirements
Line of sight
When using LoRa or UHF radio communication, the base and rover require a clear line of sight for a stable correction link. Buildings, terrain, vegetation, and other obstacles can reduce signal quality or interrupt communication.
Unlike radio communication, NTRIP does not require a direct line of sight between the base and rover.
Baseline length
The distance between the base and rover, known as the baseline, is limited for both radio and internet-based communication.
For radio communication, the maximum supported baseline depends on the Reach model, radio type, setup details, and surrounding environment. Refer to your Reach model datasheet for the supported range.
When you use an NTRIP service or Emlid Caster, the base sends raw GNSS data to the rover over the internet using the NTRIP protocol. In this setup, the baseline should generally not exceed 60 km. However, RTK positioning assumes that the base and rover operate under similar atmospheric conditions. As the distance between them increases, atmospheric differences can introduce errors and reduce positioning accuracy. For best results, keep the baseline between the base and rover as short as possible.
Electromagnetic interference
Local electromagnetic interference can affect both GNSS reception and radio communication. To ensure reliable operation, keep the base and rover away from strong interference sources such as power lines, radio transmitters, large motors, and communication equipment.
Coordinate system
The base station defines the coordinate system for your survey data. All rover measurements are calculated in that same coordinate system.
If the base station is defined in a different coordinate system than the one required for your project, every measured point will be shifted by the same horizontal and vertical offset. Because of this, the coordinate system configured for the project in Emlid Flow on the rover must match the coordinate system used by the local base or NTRIP service.
Coordinate system mismatches are one of the most common causes of GNSS surveying errors. Before starting work, verify that:
- the base coordinates are defined in the correct coordinate system,
- the rover project uses the correct coordinate system,
- and any localization or transformation parameters match the project requirements.
Learn more about base setup and coordinate system configuration for your project in the following guides:
Verifying these settings before going to the field is one of the easiest ways to prevent systematic positioning errors.