What a survey instrument needs from a ranging module
A total station or a handheld GIS device ranges to a prism or a surface and then combines that distance with two angles. The module’s job is to deliver a distance whose error is known and repeatable — not merely small. A ±1 m module that is consistently ±1 m can be calibrated against a known baseline. A module that scatters between 0.2 m and 3 m cannot, no matter what the datasheet says.
That is the first thing to test on any candidate module: repeatability on a fixed target, in the conditions you will work in, at the distances you care about. The accuracy specifications article explains why ±m and ±% describe different things.
Modules used in field measurement and mapping
| Model | Published range | Price | Role |
|---|---|---|---|
| LR2000E2 | 4–2,000 m | $120 | Entry 2 km line for handheld or tripod instruments |
| LRF3000A1 | ≥ 3,000 m at 70% reflectivity on a building target, visibility ≥ 4 km | $200 | 3 km at a low unit cost; the workhorse long-range 905 nm part |
| LRF1500H | 0.05–1,500 m at 90%; 0.05–300 m at 10% | $400 | Industrial head, 9–36 V DC, centimetre output |
| LRF0305C | ≥ 4,000 m at 60% reflectivity; building target ≥ 3,000 m at 30% | $300 | Eye-safe 1535 nm, long range in a small aperture |
| LRF0815C | ≥ 8,000 m to a 2.3 × 2.3 m target at 30% reflectance, visibility ≥ 10 km | $900 | Multi-kilometre eye-safe long range |
| LRF1830C | ≥ 18,000 m to a 3 × 3 m object, line of sight, visibility ≥ 26 km | $3,500 | Exceptional standoff; the conditions matter as much as the number |
The three errors nobody puts on the datasheet
- Beam-footprint averaging. On a slope or a wall corner the return comes from the nearest illuminated patch, not the centre of the beam. The reading is a distance to something, but not necessarily to the point the crosshair is on. See beam divergence and spot size.
- Mixed returns. When a beam covers both a wall and the foliage in front of it, some modules report the first return, some the last, some the strongest. The choice must be known and documented. Mixed returns.
- Request/response pairing. In continuous mode, frames arrive asynchronously. If the host matches a distance to the wrong timestamp, the error appears as a jump that only shows up when the instrument is moving. Timestamps and request matching.
905 nm or 1535 nm for field work
905 nm costs less per metre of range and the modules start at $80. 1535 nm puts much more pulse energy through a small aperture while remaining eye-safe, which is why the multi-kilometre models are all in that family — and why they start at $300 and climb to $3,500. For a handheld working to 1–2 km, 905 nm covers the job. For standoff work in the kilometres, the 1535 nm line exists precisely for that.
Next step
Send the working distance, the target type, the accuracy you can tolerate and the instrument’s power budget to tommy@erdimail.com. See also choosing range and accuracy for gimbal payloads.
Where two source documents for a model conflict, the model page states the conflict rather than choosing one value, and the current datasheet governs the order.