LiDAR Point Density: How Repetition Rate Sets It
Point density is measurements per square metre. It comes from three things: how fast the laser fires, how fast the platform moves, and how far away the surface is.
The arithmetic
A single-point sensor at 1 kHz produces 1,000 range measurements per second. Mount it on a vehicle doing 10 m/s with a 0.5 mrad beam: the beam footprint at 200 m is about 10 cm, and the platform moves 1 cm per millisecond. Point spacing along the track is then set by speed divided by rate, and across the track by the scanner.
Double the rate and you halve the spacing, but only in the direction the beam travels. Density also falls with range squared, because the footprint grows in both directions.
Where the rate comes from
The ER10 runs 5 kHz at 10 µJ; the ER40 runs 1 kHz at 40 µJ; the ER70 runs 500 Hz at 70 µJ. Higher rate costs energy per pulse, because the gain medium has less time to recover.
So the question isn't "how many hertz can I get". It's how much energy per pulse your link budget needs, and therefore how much rate is left.
What actually limits density
Three practical limits, in order: energy per pulse at the working range, timing precision in the receiver, and the stability of the platform.
A dense point cloud from loose pointing accuracy is just noise with a nice resolution. If the gimbal moves more than the beam spacing between shots, the extra points don't add information.
Rule of thumb
Work out the energy you need at the target first. Take the highest rate that still delivers it. Then check that the platform's angular stability supports the spacing you just bought.
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