LiDAR : Light Detection And Ranging Sensor — Chapter 1
Deep dive into 3D lidar , history and its application together.
My first encounter with LiDAR was when I started working on a project for Autonomous Navigation. Being an Electronics Engineer, I am always fascinated about sensor and its application.
A year back I stared working on LiDAR. This will be a series of blogs about LiDAR to share my knowledge that I have gained over a period of time.
Unmanned system , we can call it as Autonomous system such as Robots and Self-driving cars , operate without human interface. Autonomous system requires to do the following : Sense the environment , present state of system variable , location :Determine what action to take next and make a plan , consider safety criteria , avoid situation that create a risk to human safety , or the autonomous system itself.For sensing the environment , Multiple sensors are used and while choosing the sensor their feature play main role.
What is “LiDAR “ ?
LIDAR stands for ‘Light Imaging Detection and Ranging’. Just as sonar uses sound waves and radar uses radio waves to create a map of the environment, LiDAR uses Light.
When was “Lidar” invented ?
LiDAR, was first used in the 1960's when laser scanners were mounted to aeroplanes .This got more popular during the 1980's after the introduction of GPS for calculating accurate geospatial measurements. Now that Application of LiDAR spread across many fields.
How does it work?
Working principle of LiDAR is same as RADAR.Lidar technology measures the distance between itself and a target. Light(LASER) is emitted from the LiDAR and travels to a target. It will reflect off of its surface and comes back to its source. As the speed of light is a constant value, the LiDAR is able to calculate the distance to the target.
Knowing the position and orientation of the sensor, the XYZ coordinate of the reflective surface can be calculated, represented by a point. By repeating the same process many times, creates a map of all point that LiDAR received. This map is called as Point cloud.
Does Lidar have categories?
Yes, Lidar categories is distinguish between the Dimension same as RADAR , 1D , 2D and 3D. “D” correspond to Dimensions.
- 1D lidar consist of still laser beam that calculate the distance between an obstacle and the scanner on one axe so one dimension.
- 2D LiDAR consist of one laser beam which has a spin(rotating) mechanism, which collect horizontal distance to the targets to get data on X and Y axes.
- For a 3D LiDAR, the idea is the same, but several laser beams are vertically stacked and are shot to get data on X, Y and Z axes. Each laser beam will have an angle delta with the other beams.
1D and 2D lidar mainly used in Robots technology , But 3D lidar used in advanced robotic system to emulate humans.
Features of LiDAR :
Top features of lidar is as follows:
Field of view : Lidar has 360° FoV. Having wide FoV is important for Autonomous system to navigating safely in environment.
Range : Range is feature which will define how far the objects can be detected.More the range of Sensor , autonomous system will detect the object and take the required action within safety time.At highway speeds , a minimum of 100meters allows the vehicle the time it needs to react to changing road conditions and surroundings.
Resolution : Resolution plays main role to identifying object ; more the resolution , more the information we can get like size , shape and location of objects. High resolution LiDAR is critical for object detection and collision avoidance at all speeds.
Vertical Field of view : Its is another best feature lidar has which helps in real life driving needs. Rather than considering only one plane of object , we need to have information about tall objects , road signs and driving different slops of roads.
Channel size : More the number of channel , better the object created. Below figure show the person detection using Velodyne lidar of puck 32 and puck 16 model, (32 and 16 are the channel of respective lidar) from10 meter distance.
LiDAR has many advantages over other sensor is as follows:
- Lidar data can be collected real time with high accuracy (Generally at 10/20 HZ rate)
- Lidar data can be easily fused with many sensors like camera , GPS. Sensor fusion helps to overcome the lidar cons.
- Lidar technology works well even in dark places to detect objects.
I am Electronics Engineer .I found Sensor fusion and Data science field fascinating.I am currently working as AI engineer.I hope to contribute to this growing Data Science Society. You can connect with me on LinkedIn.
