How to Configure GNSS Correction on Site
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A GNSS receiver can show a strong satellite signal and still deliver unusable survey data if its correction source, coordinate reference system or site calibration is wrong. Knowing how to configure GNSS correction properly is therefore less about finding a menu option and more about building a reliable chain from satellites to the coordinates required on site.
For surveyors, engineers and construction teams, that chain needs to be checked before setting out starts. A missed datum setting can shift results by metres. An unstable mobile-data connection can interrupt RTK fixes. A correction age that is quietly increasing can leave a team working with reduced confidence when time is tight.
Start with the correction method that suits the job
GNSS correction reduces the errors caused by satellite orbit variation, atmospheric delay and timing. For most professional surveying and setting-out work, the aim is an RTK fixed solution that provides centimetre-level positioning in real time.
The usual choice for a mobile rover is a network RTK correction service. The receiver connects to a network of permanent reference stations using its internal SIM, a controller SIM or a mobile hotspot. It receives corrections through the internet, commonly using the NTRIP protocol. This is practical for work spread across multiple locations, provided there is dependable mobile coverage.
A local base station and radio link can be a better fit where mobile signal is poor, where the site is remote, or where a project needs an independent local control arrangement. The base broadcasts corrections directly to the rover, so there is no reliance on a mobile network. However, the base must be positioned carefully, configured correctly and protected from disturbance throughout the work.
The right method depends on the job. A network service is often efficient for topographical surveys and short-term setting out across the UK. A base and rover configuration may offer more control on a long-running infrastructure site or in an area with unreliable data coverage. In either case, correction quality is only one part of accuracy. The coordinate system and site control must also match the project requirements.
Before you configure GNSS correction
Have the necessary information available before opening the receiver settings. This prevents field teams from guessing at a mountpoint or coordinate system while a machine, subcontractor or survey crew is waiting.
You will normally need:
- Active correction-service credentials, including server address, port, username and password
- The required NTRIP mountpoint, supplied by the correction provider
- A working SIM or data connection, with the correct APN where applicable
- The project coordinate reference system, transformation and height model
- Any site control coordinates, localisation details or calibration file
How to configure GNSS correction: the field workflow
The exact labels vary between Leica, GeoMax and other professional GNSS systems, but the workflow is broadly the same. Start by connecting the controller to the receiver through Bluetooth, Wi-Fi or the manufacturer’s preferred connection method. Confirm that the receiver is charging, its antenna has a clear view of the sky and its SIM is recognised if you are using internal mobile data.
Set up the internet connection
Open the receiver or field software connection settings and select the internet source. This may be the receiver’s internal modem, the controller’s mobile data connection or a Wi-Fi hotspot. If the SIM has not been preconfigured, enter the network APN supplied by the mobile provider.
Do not assume that a displayed signal icon means the rover has internet access. Test the connection within the software, then check that the device is receiving a usable data signal at the actual working area. A receiver may work at the site office but struggle in a cutting, near dense structures or at the edge of network coverage.
Create the NTRIP correction profile
Select NTRIP as the correction method, then enter the caster or server address, port and login details provided by your correction network. Save the profile with a clear name, particularly if your organisation uses more than one service or works across different regions.
The next choice is the mountpoint. This tells the receiver which correction stream to use. Networks may provide options for VRS, nearest-reference-station or MAC correction streams, as well as different data formats. For modern equipment, RTCM 3 is a common choice, but use the stream recommended by the provider and supported by your receiver.
A VRS mountpoint is often a sensible option for rover work because the network models corrections for an estimated position near the receiver. Some services require an approximate position before they can return the most suitable correction stream. Leave the rover stationary in open sky while the connection establishes and avoid moving immediately after connecting.
Once connected, check the correction status rather than relying on the connection message alone. You want to see a current correction stream, a low correction age and, after initialisation, an RTK fixed position. A float solution may be adequate for reconnaissance, but it is not the same as a verified fixed solution for survey control or precise setting out.
Configure the coordinate system before collecting data
This is the point where otherwise good GNSS work can go wrong. The correction network provides position information in a global or European reference frame, commonly related to ETRS89. Your drawings, control and deliverables may instead be on a national grid, a project grid or a local engineering coordinate system.
For much work in Great Britain, the required output will be British National Grid with a suitable transformation from ETRS89 to OSGB36, and an appropriate geoid model for orthometric heights. The exact transformation and geoid depend on the software, project specification and the client’s control framework. Select the approved settings rather than a similarly named default option.
Do not treat horizontal coordinates and heights as one decision. A point can appear correct in eastings and northings while the level is wrong because ellipsoidal heights have been used instead of orthometric heights. Where finished levels, drainage or machine control are involved, check the vertical reference against known control before work begins.
If the project uses a site grid, load the approved localisation or calibration. Where no file exists, establish it from well-distributed control points and retain a record of the residuals. A two-point fit can make the display look right, but it provides limited evidence that the site is properly aligned. More control across the working area gives a much stronger check, especially on large or elongated sites.
Verify against independent control
A fixed RTK status is not a final quality check. Occupy at least one known point after configuration and compare the measured position with its published or project coordinate. Where practical, check a second point elsewhere on site.
Look at the difference in eastings, northings and height separately. A consistent horizontal offset often indicates the wrong coordinate system, transformation or calibration. A height difference may point to the wrong geoid, an incorrect antenna height, or control based on a different vertical datum. A result that changes each time you occupy the point may indicate multipath, poor sky visibility, unstable corrections or an issue with the control itself.
Record the test result, correction source, mountpoint, coordinate system and antenna-height method in the site notes. This gives the next operator a clear configuration record and makes later checks much easier if a discrepancy is reported.
Configuring a local base and radio corrections
With a base and rover arrangement, configure the rover’s radio channel, protocol and network ID to match the base. Set the base over a known control point whenever possible, enter or measure the antenna height correctly, and confirm whether coordinates are being entered in the project grid or a global reference frame.
If the base is set on an assumed coordinate, all rover positions will be relative to that assumption. This can be useful for local earthworks or volume checks, but it should never be confused with positions tied to the national grid or verified project control. If the base is moved, bumped or restarted with different coordinates, recheck the entire setup.
Radio range is affected by terrain, plant, buildings and antenna position. Place the base antenna where it has a clear view of the rover work area and avoid mounting it close to large metal surfaces or active radio equipment. For critical work, test the working extent rather than trusting a quoted range.
Diagnose common GNSS correction problems
When the receiver will not achieve a fixed solution, begin with the simplest checks. Confirm that the subscription is active and the username, password and mountpoint are correct. Then check mobile data, correction age, satellite availability and whether the receiver has a reasonably clear view of the sky.
If corrections are arriving but the solution remains float, allow time for initialisation in a static position. Move away from trees, scaffold, vehicles and reflective building façades that can create multipath. A long baseline to a single local base can also reduce reliability, whereas a network solution may perform better over wider areas.
If the rover fixes but points are in the wrong place, do not attempt to correct the problem by applying an arbitrary shift. Stop, review the coordinate system, transformation, geoid and localisation, then compare against independent control. An apparently small workaround can create a larger issue once data reaches design, machine control or as-built records.
A well-configured GNSS rover should feel routine in use, but that routine is earned through repeatable checks. Survey Tech can support teams with equipment selection, setup advice, training and servicing, so the receiver, correction method and project workflow work together from the first occupation of control to the final deliverable.
The most useful habit is simple: treat every new site, subscription and project grid as a fresh verification exercise. A few measured minutes at the start of the shift can protect a full day of accurate work.