What a total station does
A total station measures three things to fix any point in 3D: a horizontal angle, a vertical angle, and a slope distance to a target. From these it computes coordinates. It is, in effect, an electronic theodolite fused with an EDM (Electronic Distance Meter) and an onboard computer.
The distance is measured by the EDM, which sends an infrared or laser beam to a prism (or, in reflectorless mode, to a surface) and measures the time or phase of the return. The angles come from precision electronic encoders. Combine angle + angle + distance and you have a point — repeated thousands of times, that is a topographic survey, a setting-out job, or an as-built.
The three families: manual, robotic, scanning
| Type | Operation | Crew | Best for |
|---|---|---|---|
| Manual | Operator aims at every point | Two people | Budget, occasional use |
| Robotic | Motorised, auto-tracks the prism | One person | Productivity, stakeout |
| Scanning | Captures dense point clouds | One person | Detail, BIM, complex sites |
Manual total station
The classic two-person setup: one operates the instrument, one holds the prism pole. Reliable and affordable, ideal for occasional or budget-constrained work.
Robotic total station
A motorised instrument that locks onto and automatically follows the prism, controlled remotely from the pole. One surveyor does the work of two — the single biggest productivity gain in modern field surveying, and the reason robotic models dominate stakeout.
Scanning total station
Combines conventional measurement with high-speed scanning that captures thousands of points per second, producing a point cloud alongside discrete measurements. The output is a point cloud alongside discrete measurements, bridging classic surveying and reality capture.
Reading accuracy specs: angle and distance
Every total station is rated by two numbers. Misreading them is how people overpay or under-spec.
Angular accuracy (in arcseconds)
Quoted in seconds of arc (″). Smaller is better, and the practical impact grows with distance:
| Angular spec | Error at 100 m | Typical use |
|---|---|---|
| 1″ | ~0.5 mm | Monitoring, precise control |
| 2″ | ~1 mm | Engineering, general control |
| 5″ | ~2.4 mm | Topographic, construction |
| 7″ | ~3.4 mm | General construction |
Distance accuracy (EDM)
Written as a constant plus a parts-per-million term, e.g. (2 mm + 2 ppm). The constant is fixed; the ppm part grows with distance — 2 ppm adds 2 mm per kilometre. At normal survey ranges the constant dominates, so a 1–2 mm instrument is excellent. Reflectorless ranging is convenient for inaccessible points but is slightly less accurate and depends on the surface.
Total station vs GNSS: which and when
These are complementary tools, not rivals. The best field crews carry both and switch by situation.
| Total Station | GNSS | |
|---|---|---|
| Needs sky view | No — works indoors, under cover | Yes — needs satellites |
| Needs line of sight | Yes — to the target | No |
| Relative accuracy | Excellent (mm) | cm-level (RTK) |
| Speed over open ground | Slower | Very fast |
| Tunnels / indoors / forest | Works well | Struggles or fails |
Use GNSS to cover open ground fast and to establish control; use the total station for millimetre detail, indoor and underground work, and anywhere the sky is blocked. The classic workflow ties the total station setup to GNSS-measured control points, getting the speed of GNSS and the local precision of the total station. Both ultimately depend on a correct coordinate system — see the Coordinate Systems guide and the EPSG Explorer.
Setting up correctly: the fundamentals
- Level over the point. Centre the instrument precisely over the station mark with the optical or laser plummet, then level it with the electronic bubble. Errors here propagate into every measurement.
- Establish orientation. Measure to a known backsight so the instrument knows its bearing. Garbage orientation means garbage coordinates, even with a perfect instrument.
- Enter the correct instrument and target heights. A mistyped prism height is one of the most common — and invisible — sources of error.
- Measure in two faces for control. Observing on both telescope faces and meaning the readings cancels several systematic errors.
- Check into a known point. Always verify against an independent control point before trusting the setup.
Atmospheric conditions matter too: temperature and pressure affect the EDM, so set the ppm correction for precise long-range work. Terms used here are defined in the surveying glossary.
How to choose a total station
Buy for the work you actually do, not the spec sheet's headline number:
- Angular accuracy — 2–5″ suits most engineering and topographic work; 1″ for monitoring and precise control.
- Manual vs robotic — robotic pays for itself fast if you stake out regularly or want one-person crews.
- Reflectorless range — matters if you measure many inaccessible points (facades, cliffs).
- Scanning — worth it for detail-heavy, BIM or as-built work.
- Software and data flow — onboard apps and clean export to your CAD/field software save real hours.
Compare models and specifications across brands in the surveying instruments database and research makers in the manufacturers directory. For the GNSS side of a combined workflow, start with the GNSS Surveying guide.
Frequently Asked Questions
What is a total station used for?
A total station measures horizontal and vertical angles plus distance to fix points in 3D to the millimetre. Surveyors use it for topographic surveys, setting out (stakeout) of construction, as-built measurement, deformation monitoring and any precise work where line of sight to the target is available.
What is the difference between a manual and a robotic total station?
A manual total station needs an operator to aim at every point, so it requires a two-person crew. A robotic total station is motorised and automatically tracks the prism, letting one surveyor control it remotely from the pole — roughly doubling productivity and making it the standard for stakeout.
What does an accuracy spec like "2 mm + 2 ppm" mean?
That is the distance (EDM) accuracy: a fixed 2 mm error plus 2 parts per million of the measured distance, which adds 2 mm per kilometre. At normal survey ranges the fixed part dominates, so the instrument is accurate to a couple of millimetres.
What does angular accuracy in arcseconds mean?
Angular accuracy is quoted in seconds of arc; smaller is better. The ground error it causes grows with distance — a 5″ instrument gives about 2.4 mm of error at 100 m, while a 1″ instrument gives about 0.5 mm. Choose 1–2″ for monitoring and precise control, 5″ for general topographic work.
Should I use a total station or GNSS?
They are complementary. GNSS is faster over open ground and needs no line of sight but requires a clear sky view, while a total station gives millimetre relative accuracy and works indoors, in tunnels and under tree cover where GNSS fails. Most crews use GNSS for control and open areas and the total station for precise detail.
Why measure in two faces?
Observing a point on both faces of the telescope and averaging the readings cancels several systematic instrument errors, such as collimation and trunnion-axis errors. It is standard practice when establishing control or any time the highest angular accuracy is required.