RTK Survey (Real Time Kinematic): Centimetre Fixes

What is an RTK survey?

RTK, or Real Time Kinematic, is a satellite-based positioning method in which a rover receiver applies carrier-phase corrections from a base station or network as it moves. It solves the whole number of signal wavelengths to each satellite. When that ambiguity is resolved the solution is called fixed and reaches roughly 1–2 cm horizontally; before that it is float, with decimetre-level error.

How does an RTK survey work on site?

The base sits on a control point and the rover visits every feature; the controller shows fixed or float before each shot is stored. Corrections travel by UHF radio from our own reference station, or over mobile data from a network. In India, Survey of India's national network of ground-based reference stations supplies network RTK corrections; read CORS Network in India for how that service works. The satellites themselves are covered in GNSS Explained for Surveyors.

• Accuracy falls slowly with distance from the base, so single-base RTK is kept within about 10–15 km.
• Trees, tall buildings and metal roofs block or reflect GPS signals, so the rover may stay float.
• Good practice re-observes a known point at the start and end of each session.

RTK, static and network RTK compared

Many route jobs pair RTK control with a scan for buried services; if yours does, check the cost in our calculator.

An example from a plot survey

On a five-acre plot near Ballabgarh, a base on a static-observed control pillar lets the rover pick 60 boundary and detail points in a morning. Two corners under a mango grove stay float. Those are completed from the fixed points by total station instead, a common split described in total station survey rates and scope. Every point is stored with its fix status, so the drawing never mixes float and fixed values without saying so.

What goes wrong most often on an RTK job?

Set-up errors, not satellite errors, spoil most RTK surveys. The rover can only be as right as the base it trusts and the numbers typed into the controller.

• Wrong base coordinates. A pillar value typed in the wrong zone or datum shifts every point by the same amount, and the survey still looks internally perfect.
• Antenna height slips. Entering a slant height as vertical, or 1.80 m for 1.08 m, moves every reduced level by the difference.
• Accepting float as fixed. A controller set to store automatically can record decimetre points without anyone noticing.
• Working beside reflectors. Metal sheds, glass façades and water tanks bounce signals and bias the fix by centimetres.

A worked check that catches a bad base

A second known point, observed before the real work, exposes most set-up errors in minutes. Say the base occupies pillar CP-1 and the rover then visits pillar CP-2, whose coordinates came from the same static survey. If CP-2 comes back 0.012 m east and 0.009 m north of its published value, the set-up is sound. If it comes back 1.000 m south, the base northing was mistyped by a metre, and correcting it before the first boundary point saves a morning of rework. The same check at the end of the session shows that nothing moved while the crew worked.

What a Mezux RTK point list contains

Every point carries its coordinates and the evidence of how good they are. Our CSV and Excel files list point ID, easting, northing, reduced level and feature code. Each row also gives fix status, the receiver's horizontal and vertical precision estimates, and whether corrections came from our base or from a network. The report adds the start and end check-point results, datum, zone and geoid model. Corrections themselves travel in RTCM 10403 (version 3) messages, often over NTRIP, and ISO 17123-8 describes a field procedure for testing GNSS RTK equipment that suits periodic instrument checks.

Is RTK the same as DGPS?

Not strictly. Classic DGPS (differential global positioning system) corrects code measurements and gives results of about a metre or better; RTK uses the carrier phase and gives centimetres. In Indian contracts, though, a "DGPS survey" means a base-and-rover carrier-phase survey, RTK or static, which is how modern DGPS works on Indian sites. For the method and figures behind ours, ask a survey engineer for your project.

Frequently asked questions

What does a float solution mean?

The rover has corrections but has not resolved the carrier ambiguities. Positions are good to decimetres, not centimetres, and should not be used for boundaries.

Does RTK work under trees?

Poorly. Canopy blocks and scatters signals before they reach the GPS receiver. Points under trees are better completed by total station from nearby fixed points.

Who can do an RTK or DGPS survey for my plot?

We use our own base and rover sets; see who to call for DGPS survey for scope and timing.

How long does the rover stay on each point?

A few seconds once fixed for detail, longer for control. For boundary corners we often take two separate occupations a few minutes apart and compare them.

What is a check shot?

An observation on a point of known value, made to prove the set-up. It is done at the start, at intervals and at the end of each session.

Can RTK be used to set out a building?

Yes, for grid lines and corners in open ground. Close to tall structures, setting out is finished by total station from RTK control.

Is RTK affected by weather?

Heavy cloud and rain have little effect on the signals. Ionospheric activity, which varies through the day and the solar cycle, matters more and can slow fixing.

Written by Saniya Parveen · Technically reviewed by Rahul Rai · Updated 8 November 2026