Multiple Returns; Evaluation Rules; Figure 5. Sensor Emitting A Single Beam (For Example) With Multiple Returns - quanergy M8 User Manual

Multiple Returns

The M8 sensor includes the multiple returns feature that produces an enriched point cloud,
which is particularly important for 3D mapping. This feature is possible because each
emitted laser pulse can reflect off multiple objects (Figure 5) and return to the LiDAR
sensor as one or more return pulses. The M8 sensor measures and evaluates the distances
and intensities of as many return pulses as there are, follows rules for which particular
return values to report, then reports the distances and intensities of up to three of those
return values.

Evaluation Rules

The distance and intensity of each return pulse is evaluated to determine which is:
• Maximum: Has the highest intensity/amplitude.
• Second Strongest: Has the second highest intensity/amplitude.
• Last: Has the highest range, that is, the longest time-of-flight from the sensor.
The evaluation rules for assigning these labels are as follows:
• If no return pulses are detected, each of the three return values is 0.
• If one or more return pulses are detected:
– Return 0: The first return value equals Maximum.
– Return 1: The second return value equals Second Strongest. (But if there was only one
return pulse, the return value equals Maximum.)
– Return 2: The third return value equals Last, which may be equal to Second Strongest
or Maximum.
To select a specific return (0, 1, 2, or All 3), refer to "Return Data Select" on page 48.

Figure 5. Sensor Emitting a Single Beam (for example) with Multiple Returns

M8 Sensor User Guide, QPN 96-00001 Rev K Page 20