Scanning Lidar vs Radar

There are several types of sensor which are used for detecting and measuring. The most common are: PIR, ultrasound, lidar, and radar. Each of these sensors has their own areas of strength and weaknesses.

Of all the sensors most similar to radar, scanning lidar would be the closest.

The purpose of this blog post to outline in detail, the differences between scanning lidar and radar and to answer the question: If I'm currently using scanning lidar, why should I consider radar? What are the benefits?

Lidar

Lidar is a technique which involves shooting very specific beams of light at an object and then measuring how long it takes for that beam of light to be reflected back to the sensor (time of flight). Scanning lidars basically put this functionality on a motor and spin it around at speed. The result is a 2D map of the surroundings. 

Radar

Radar is a detection system that uses radio waves to determine the range, angle, and velocity. It is mature mature technology which has been used from everything from forecasting the weather to monitoring vital signs of humans. Radar works by sending high frequency 'chirps' of radio waves then receiving responses which then get processed to produce 3D information about whatever is in front of it.

Radar

Pros

  • Good at detect moving objects.
  • Works in any lighting environment.
  • Works in any environmental conditions (fog, dirt, rain, etc).
  • Can see through solid objects such as walls.
  • Can see very long distances (depending on configuration).
  • Fast update rate.
  • No moving parts.
  • Can detect transparent objects.
  • High quality radar is now affordable.
  • 110 degree field of view.
  • Good at detecting objects in 2D as well as 3D.
  • Distance, speed and acceleration can be measured.

Cons

  • Poor angular resolution.
  • Poor at detecting static objects.
  • Data can often be "noisy" due to spurious reflections.

Scanning Lidar

Pros

  • Great at measuring distances accurately.
  • Good angular resolution.
  • Good at detecting static objects and building a 2d map of an environment.
  • 360 degree view.
  • Low-end scanning lidar modules are affordable.
  • Good support using 3rd party tools such as ROS and Octomap.

Cons

  • Spinning mechanical parts will eventually need maintenance / wear out.
  • In order to get the 360 degree view, mounting positions are limited.
  • The sensor can struggle in bright environments.
  • The sensors do not work well in rain, fog, or smoke.
  • Only a 2D map can be produced.
  • The sensor cannot see transparent objects.
  • The sensor has a shorter range than radar (depending on configuration).
  • The update rate is limited due to spinning mechanism.
  • The sensor is not that good at detecting moving objects.

So as you can see there are clear pros and cons of each type of sensor. If you are looking for a radar sensor for you next project, checkout the RadarIQ M1 Sensor