6
Setup reliability
6.1
Ranging on the floor to determine the threshold
Reliability of the algorithm relies on the accuracy of the setup which detects the distance between the sensor
and the floor. This can be ensured only if nothing (e.g. no obstacle or static object) blocks the front and back
FoVs. To assess if a setup is reliable, a significant number of distances can be measured with the sensor. Then, a
histogram diagram can be established to confirm that the sensor is correctly set up and that no target is within its
FoVs.
A threshold needs to be defined, which is achieved after having ranged on the flooring material over a significant
number of samples. In fact, the threshold should be chosen so that all the measured distances (when ranging
the floor) are greater than this threshold. We recommend that at installation of the application, an autocalibration
routine is launched to calculate the threshold. This is because flooring material can be different in many locations.
Figure 9. Histogram of 3500 measured distances
describes an example of such a calibration for the use case
illustrated in
Figure 8. People counting at 2345 mm distance from the floor
. The distance between the sensor and
the floor is 2345 mm, and as the minimum distance measured by the sensor is 2290 mm, the threshold is thus
less than 2290 mm.
Note:
This calibration should be performed in the worst ambient light conditions, to maximize the jitter and obtain a
threshold that is relevant to all possible ambient lighting conditions the counting setup is exposed to.
Figure 8.
People counting at 2345 mm distance from the floor
UM2600
Setup reliability
UM2600
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Rev 2
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