The Evolution of Sensing

The Evolution of Sensing

Object tracking has evolved over the last few decades.

PIR sensors have been around for a long time. PIR Sensors are good at detecting movement. They don't track objects, just detect there has been some movement in a particular area.

Ultrasound was the first technology to become readily available for makers to use in terms of object tracking. While ultrasound can detect objects, it is rather underwhelming. Limited range, lack of resolution, and only being able to detect one thing at at time*. Ultrasound lacks the robustness and features to be used beyond basic projects.

LiDAR was the next technology for tracking objects to come along. LiDAR essentially replaces sound with light and while it has a much greater range than ultrasound, it still suffers from limitations - the key one being low resolution when it comes to working out the lateral position of objects.

The ability of LiDAR to know a position was improved by placing a sensor on a motor and spinning it around (Scanning LiDAR). While this provides good resolutions, it still takes a considerable computational processing and additional tools such as octomap to properly detect objects.

mmRadar technology is now becoming available for the first time. mmRadar sensors are small, fast and are ideally suited to tracking objects.

Here is a summary of the capabilities of each type of sensor, used for object tracking:


PIR Sensor



Scanning Lidar


Works in a dark environment

Yes Yes Yes Yes Yes

Works in a very bright environment

Yes Yes No No Yes

Sees through transparent objects

No No Yes Yes Yes

Sees through solid objects

No No No No Yes

Can detect transparent objects

No Yes No No Yes

Sees through dust/smoke/steam

No No No No Yes

Stable readings across temperatures

Yes No Yes Yes Yes

Detects objects more than 10m away

No No Yes Yes Yes

Measure speed accurately

No No No No Yes

Good for detecting small object

No No No Yes Yes

Fast data capture

No No Yes Yes Yes

Can be used to create high resolution images

No No No Yes No

Can be used to create low resolution images

No No No Yes Yes

Can track multiple objects at once

No No No Yes Yes

No moving parts

Yes Yes Yes No Yes

* There are a range of sensors, from different manufacturers each with slightly different capabilities. The summary here is a generalization.

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