What a drone altimeter actually needs from a rangefinder
A laser altimeter on a UAV is a different measurement problem from a handheld rangefinder. The target is the ground, not a building; the ground moves; the sensor is bolted to something that vibrates, tilts and is trying to land. Three numbers decide whether a module works in that job: the minimum range (the last metre before touchdown), the update rate the flight controller can consume, and the range figure at the reflectance of real terrain rather than a white wall.
This page lists the ERDILRF modules used for altitude and terrain sensing, with their published prices and the conditions behind each range figure. Every number below is copied from that model’s own record.
Module shortlist for UAV altitude and terrain sensing
| Model | Published range | Price | Why it fits an airframe |
|---|---|---|---|
| LRF50VB | 0.05–50 m at 90% reflectivity; 0.05–20 m at 10% | $140 | Short-range terrain following and precision landing; the 0.05 m floor matters for the last metre |
| LRF200H | 0.05–200 m at 90% reflectivity; 0.05–70 m at 10% | $250 | Industrial DToF head, 9–36 V DC supply, centimetre output |
| LRF300H | 0.05–300 m at 90% reflectivity; 0.05–100 m at 10% | $280 | Same family, more headroom for takeoff and climb |
| LRF600H | 0.05–600 m at 90% reflectivity; 0.05–200 m at 10% | $350 | Higher-altitude mapping passes and long approach paths |
| LRF1500H | 0.05–1,500 m at 90% reflectivity; 0.05–300 m at 10% | $400 | The UAV variant in the H series: altitude at distance, still with a 0.05 m floor |
| SPD1200N3 | 3–1,000 m | $94.5 | Single-photon ranging at the lowest price point; 3 m minimum range rules it out for landing |
| LRF3000A1 | Long range on a building target in clear weather, visibility ≥ 4 km | $200 | Long standoff terrain reference, not a landing sensor |
The pattern is worth stating plainly: the two columns of numbers for each H-series model are the same sensor under two conditions. On a wet runway or dark asphalt the second column is the one that applies, not the first. If your terrain is grass, water or snow, plan against the low-reflectance figure.
Interface and integration path
Most ERDILRF modules present a UART interface with a documented frame and checksum; the H series runs from 9–36 V DC, which is a different supply arrangement from the 3.3–5 V modules. Before wiring anything to a flight controller, confirm three things in the model’s own document: the logic level, the frame format, and the power-up behaviour of the enable pin.
- PX4 rangefinder integration: three routes — the driver route, the distance-sensor route and the serial-protocol route, and when each one applies.
- Connect a UART laser rangefinder to Pixhawk / ArduPilot — wiring and parameter side.
- Enable pins: polarity and wake time — the pin that silently costs a second of flight time.
- Rangefinder update rate for moving platforms — what the loop can actually keep up with.
- Open drivers — Python, Arduino and ROS 2 packages with the protocol documents.
What the datasheet will not tell you
Three failure modes dominate UAV altimeter complaints, and none of them appear as a specification:
- Beam divergence over a sloped surface. A cone that is a few centimetres wide at 10 m becomes metres wide at several hundred metres. On a slope, the return comes from the nearest part of the footprint, not the point under the aircraft. See beam divergence and spot size.
- The blind zone near the ground. Every module has a minimum range. Landing guidance has to hand over to another sensor — barometer, ultrasonic or a vision system — below it.
- Optical contamination. Dust, prop wash and lens fog are a mechanical problem that shows up as a ranging problem. See protective window acceptance.
Choosing between 905 nm and 1535 nm for a UAV
905 nm silicon receivers are cheaper, and the 905 nm line starts at $80. 1535 nm is eye-safe at much higher pulse energy and reaches multi-kilometre distances in a smaller aperture, but the modules start at $300. For altimetry below a few hundred metres, the 905 nm line covers the requirement at a lower unit cost; for standoff terrain reference at kilometres, the 1535 nm line is the one that reaches. The comparison is worked through in 905 nm vs 1535 nm for UAV gimbals and payloads.
Next step
Send the airframe, the altitude band you need to measure, the terrain type and the flight controller to tommy@erdimail.com, or use the sample request form. We will answer with a specific model and the conditions behind its range figure, within one business day (Chengdu, UTC+8).
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.