If your rover keeps dropping to RTK float, or your maps are consistently shifted by a few centimetres, the problem is often the base station, not the rover. Here is a checklist for setting up a base that your rovers can trust.
Disclosure: I work at Eview GNSS, which makes Septentrio-based receivers, including base stations.
1. Decide: your own base or a network service?
- Network RTK (NTRIP): no hardware to install, but it needs mobile data at the rover, often a subscription, and its accuracy depends on the distance to the nearest reference station.
- Your own base: you control the coordinates and the uptime, and it works over a UHF radio where there's no mobile coverage. You pay for that with one more box to install and look after.
A rule of thumb: RTK error grows by roughly 1 ppm of the baseline, so keep rovers within about 10–20 km of the base for consistent centimetre results.
2. Pick the site
- A clear view of the sky down to about 10–15° elevation, all the way round.
- Away from reflectors: metal roofs, walls, vehicles, fences and water tanks cause multipath, and a base with multipath passes that error to every rover.
- A rigid mount: a concrete pillar or a pole bolted to a structure, not a tripod that settles. If the base moves, every rover position moves with it.
- Power and a cable route you can protect. Fit lightning protection on long outdoor antenna cables.
3. Choose the antenna
The base antenna matters more than the rover antenna. Use a multi-band survey-grade antenna, ideally a choke ring or a model with good multipath rejection. Write down the exact antenna model and its height above the mark: you'll need both for the correction messages and for any post-processing.
4. Get good base coordinates
Your rovers inherit the base's coordinates, errors included.
- Survey-in / averaging: quick, but only as accurate as a standalone fix (metre level). Fine for relative work, where everything is measured against the same base. Not fine if you need to match maps or field boundaries from another day or another system.
- Known point: set the base on a surveyed mark and enter its coordinates.
- Post-processed: log several hours of raw data, process it with a PPP service or against a nearby reference network, then enter the result. This gives centimetre-level absolute coordinates.
Pick a datum (for example the national realisation of ITRF) and use it everywhere: base, rovers and GIS.
5. Configure the corrections
Most receivers output RTCM v3. A typical modern message set:
| Message | Purpose |
|---|---|
| 1005 or 1006 | Base antenna reference point (1006 adds antenna height) |
| 1033 | Receiver and antenna descriptors |
| MSM4 or MSM7 (1074/1084/1094/1124 or 1077/1087/1097/1127) | GPS, GLONASS, Galileo and BeiDou observations |
| 1230 | GLONASS code-phase biases |
MSM4 is smaller and usually enough for RTK. Use MSM7 if bandwidth allows or your rover benefits from the full observations. Send 1 Hz observations and the reference-point message every few seconds.
6. Choose the link
- UHF radio: works anywhere, a few km on open ground (more with a high antenna or a repeater), and no mobile data needed.
- NTRIP: the base pushes RTCM to a caster over the internet, and rovers pull it over mobile data. Range is limited only by the baseline rule above.
- Wi-Fi or Ethernet: useful for a fixed site such as a yard, depot or test field.
Whichever you choose, watch the latency and the dropouts, not just the range. A late or patchy correction stream is a common cause of float.
7. Log raw data at the base
Log raw observations (and export RINEX) at the same time as streaming RTCM. If the radio link drops during a mapping flight or a field run, you can still post-process (PPK) the rover against the base log. This costs a memory card and saves a re-flight.
8. Verify before you trust it
- Put a rover on a known point (or the same point on different days) and compare.
- Check the rover's fix rate and time to fix across your working area, not just next to the base.
- Re-check the base coordinates after any move, storm or change to the mount.
Quick troubleshooting
| Symptom | Likely base-side cause |
|---|---|
| Rover stays in float near the base | Multipath at the base, an obstructed sky, or missing constellations in the message set |
| Everything shifted by the same few cm or m | Wrong or averaged base coordinates, or a datum mismatch |
| Fix comes and goes | Radio or NTRIP dropouts, or high latency |
| Height offset | Antenna height or antenna model entered wrongly |
If you are building this into a robot, drone or farm fleet, we've written more on correction formats and integration (NTRIP, RTCM, RINEX), and the HB62 base station receiver is our own rugged base option.
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