How RTK positioning works

Real-Time Kinematic positioning relies on carrier-phase measurements from multiple GNSS constellations, including GPS, GLONASS, Galileo, and BeiDou. A base station or a network correction service sends real-time corrections to the rover receiver, allowing it to resolve integer ambiguities and achieve centimetre-level accuracy. The corrections compensate for ionospheric delay, tropospheric delay, satellite orbit errors, and clock offsets. When the receiver reports a Fixed solution, the horizontal accuracy is typically between one and three centimetres, depending on conditions.

Understanding the difference between a Float and a Fixed solution is essential. A Float solution means the receiver has not fully resolved the carrier-phase ambiguities and the accuracy is at the decimetre level. A Fixed solution indicates full ambiguity resolution and centimetre-level accuracy. Only points observed with a Fixed solution should be used for precise work.

Setting up a base station and rover

Base station setup procedure

Place the base station tripod over a known control point or a point whose coordinates will be determined by static observation. Level the tripod carefully using the optical plummet and the circular bubble. Measure the antenna height from the ground mark to the antenna reference point and record the measurement method, whether it is vertical, slant, or to the bottom of the antenna mount. Enter the known coordinates into the controller, select the correction broadcast format such as RTCM 3.2, and start transmitting corrections over UHF radio or via a cellular modem.

Rover configuration

Mount the rover antenna on a fixed-height pole, typically two metres. Connect to the base station radio channel or enter the NTRIP credentials including the caster address, port, mount point, username, and password. Wait for the receiver to achieve a Fixed solution before collecting data. Monitor the number of tracked satellites and the PDOP value throughout the survey. A minimum of eight satellites and a PDOP below three are recommended for reliable results.

NTRIP correction services

Network Transport of RTCM via Internet Protocol allows the rover to receive corrections through a cellular data connection instead of a dedicated radio link. This eliminates the need to set up a physical base station and extends the operational range. Several NTRIP services operate regionally and provide Virtual Reference Station or Master-Auxiliary corrections. Before subscribing to a service, verify that it covers your project area and supports the GNSS constellations tracked by your receiver. In areas with poor cellular coverage, a local base station with UHF radio remains the more reliable option.

To connect, the rover controller needs a SIM card with an active data plan or a Wi-Fi hotspot from a mobile phone. Enter the NTRIP caster hostname, port number, and authentication credentials. Select the nearest mount point or the Virtual Reference Station option if available.

Coordinate reference systems

Every RTK survey must use the correct coordinate reference system and vertical datum for the project. Common systems include UTM zones tied to WGS84, local national grids, and engineering coordinate systems defined for a specific site. Mismatched reference systems can introduce errors of tens or even hundreds of metres. Before starting fieldwork, confirm the system specified in the project documentation, enter the correct parameters into the receiver, and check at least two known control points to verify the setup. If the residuals on the check points exceed the project tolerance, do not proceed until the discrepancy is resolved.

For projects that require orthometric heights rather than ellipsoidal heights, a geoid model must be loaded into the receiver. The appropriate geoid model depends on the country and the vertical datum in use.

Accuracy expectations and limitations

Under open sky with good satellite geometry, RTK delivers horizontal accuracy of one to two centimetres and vertical accuracy of two to four centimetres. Several factors degrade performance. Multipath interference from nearby buildings or metal structures introduces noise. Partial sky obstruction reduces the number of visible satellites and weakens geometry. Long baselines between the rover and the base station increase the residual atmospheric errors that the corrections cannot fully remove.

As a practical guideline, keep the baseline under fifteen kilometres when using a single base station. Beyond that distance, network RTK with multiple reference stations provides better accuracy. For a detailed understanding of how surveying costs relate to accuracy requirements, see our guide to surveying prices in Egypt.

RTK versus static versus PPK

RTK provides instant coordinates in the field and is ideal for topographic surveys, stakeout, and volume calculations. Static observation requires post-processing but achieves sub-centimetre accuracy over long baselines, making it the standard for control networks and deformation monitoring. Post-Processed Kinematic observation records raw data that is processed later against a base file, combining the productivity of kinematic surveying with improved accuracy because the processing software can use both forward and reverse solutions.

Choose RTK when productivity matters and centimetre accuracy is sufficient. Choose static when the project demands sub-centimetre precision or the baselines exceed fifteen kilometres. Choose PPK when cellular coverage is unreliable and corrections cannot be streamed in real time, or when the project requires a post-processing quality check on all observations.

Pre-fieldwork equipment checklist

Before heading to the site, verify the following items to avoid delays and wasted time:

  • Fully charge the receiver battery, controller battery, and carry spares
  • Confirm that the NTRIP subscription is active and test the connection in the office
  • Load the correct coordinate system, geoid model, and project parameters
  • Transfer design points, control point coordinates, and reference drawings to the controller
  • Verify that the SIM card has sufficient data balance
  • Pack the range pole, bipod, tripod, measuring tape, and field book

If you are looking for GNSS equipment for purchase or rental, EL EMAN offers a range of instruments through our surveying equipment sales service. For questions about RTK surveying projects or to request a quotation, please contact us.