RTK GNSS for Plot and Boundary Mapping

Updated 2026-11-02 · 4 min read · By the akar.earth specialist team

RTK GPS for forestry: how RTK GNSS gets centimetre positions, when you need it for plots and boundaries, and how to work under canopy in Indonesia.

RTK GNSS (Real-Time Kinematic positioning) gives centimetre-level coordinates by correcting satellite signals with a base station or correction network, compared with the several-metre errors of a phone. Carbon projects use it to fix plot centres, map boundaries and ground control for drones, so that field data lines up with satellite pixels and plots can be relocated at every verification.

Why positional accuracy matters

• Linking plots to imagery. A 10 m Sentinel-2 pixel is small. A plot centre that is 8 m off can be matched to the wrong pixel, which degrades remote sensing biomass models.
• Permanent plot relocation. Verifiers check that plots were remeasured in the same place. Lost plots increase uncertainty and invite questions about selective remeasurement.
• Boundaries and eligibility. Area drives credits. A boundary off by a few metres on a long perimeter can change area materially, and can push a parcel across a forest edge in eligibility analysis.
• EUDR and land tenure. Plot polygons overlapping forest, protected areas or neighbouring claims cause compliance and social conflicts. See EUDR polygon requirements.

How RTK works

A GNSS receiver computes position from satellite signals (GPS, GLONASS, Galileo, BeiDou). Errors come from satellite clocks and orbits, the atmosphere and multipath. RTK removes most of them by comparing the rover’s carrier-phase measurements with those of a reference station at a known point, transmitted in real time by radio or over the internet (NTRIP).

Indonesia’s geospatial agency (BIG) operates a national CORS network (InaCORS) that can supply corrections in many areas. Where mobile coverage or CORS is absent, set up your own base on a known or long-occupied point, or log raw data and post-process (PPK).

Field workflow

1. Plan points. Plot centres, plot corners if square, boundary vertices, and ground control points for drone flights.
2. Set up corrections. Test NTRIP access before travel. Otherwise bring a base and radio link.
3. Check the solution type. Only accept “fixed” solutions for centimetre claims. “Float” means decimetre-to-metre error.
4. Handle canopy. Measure in gaps, raise the antenna on a pole, extend occupation time, or establish a fixed point in the open and offset into the forest with compass and laser rangefinder.
5. Monument plots. Mark centres with durable pins or pipes and record reference trees with bearing and distance, so a team can relocate them without a receiver.
6. Record metadata. Receiver, correction source, solution type, PDOP, occupation time, operator, date.
7. Store in one coordinate system. Record the datum and projection (for example WGS 84 or the relevant UTM zone) and keep it consistent across field, GIS and registry files.

Boundaries: walk, digitise or both

For smallholder parcels, walking the boundary with RTK is accurate but slow. Many projects digitise boundaries on high-resolution imagery with the farmer, then check a sample on the ground. The right choice depends on the use: EUDR plots, carbon project areas and land-rights mapping have different tolerance for error. Capture consent and ownership at the same time; see farmer registration and consent.

Choosing equipment

You do not need survey-grade kit for every task. A practical setup for carbon and EUDR fieldwork:

• Plot centres and drone ground control: a dual-frequency RTK receiver with a correction source.
• Boundary checks and farm polygons: a lower-cost RTK or high-accuracy GNSS receiver paired with a phone app, or careful digitising on recent imagery with sample checks.
• Tree locations within plots: bearing and distance from the plot centre, which is faster and more reliable than GNSS under canopy.

Train crews to read solution status and accuracy on screen, and to record it with every point. Equipment is only as good as the protocol around it.

Common mistakes

• Accepting float solutions as RTK accuracy.
• Mixing datums, so data from one season is shifted against the next.
• Measuring plot centres under dense canopy and trusting a fix that is actually multipath.
• Not monumenting plots, so remeasurement depends on GNSS alone.
• Recording coordinates with too few decimals; the EUDR asks for at least six.

What good evidence looks like

A verifier wants a plot register with coordinates, accuracy, solution type and date; photos of plot monuments; boundary files with their source and method; and a statement of the coordinate reference system. For Verra projects, check the current Geolocation File Requirements for file format and content. Show that remeasured plots match earlier positions within a stated tolerance.

RTK is the foundation for good plot sampling design and for drone ground control. We run RTK-surveyed plot campaigns through our field data campaigns service; the dMRV hub shows how positioning ties the rest of the system together.