- What is LIDAR?
- What is RADAR?
- Comparison of RADAR vs LIDAR
Massive world-renowned companies such as Tesla and Google equip their cars with laser detectors to let automobiles see other vehicles, pedestrians, and various obstacles on the road when driving. Unfortunately, these detection systems are expensive and there are much cheaper alternative devices for performing the same tasks - the question is whether the options are efficient enough to fully replace the more expensive tools in the custom solutions for automotive companies.
In this article, we will provide an overview of the LIDAR and RADAR remote sensing and determine the advantages of each system.
What is LIDAR?
LIDAR is also known as Light Imaging Detection and Ranging. It is a technology that detects objects on the surface, as well as their size and exact disposition.
LIDAR appeared on the market after RADAR and SONAR, and it uses laser light pulses to scan the environment, as opposed to radio or sound waves. The U.S. military and NASA invented the LIDAR technology more than 45 years ago for measuring distance in space, although its first commercial usage did not occur until 1995 for topographical needs.
Now, the LIDAR system design is quite compact and allows the industry to apply this technology for new purposes. A device that uses LIDAR technology is also often called the same; it is a scanner that can create a digital copy of any physical object and that can save more time as compared to starting from scratch with a drawing.
How does LiDAR remote sensing work?
An algorithm of LIDAR functioning is as follows:
- Laser signals are emitted
- Laser signals reach an obstacle
- Signal reflects from the obstacle
- Signal returns to the receiver
- and then A laser pulse is registered
The device emits laser pulses that move outwards in various directions until the signals reach an object, and then reflect and return to the receiver. In fact, this is the same principle SONAR uses, except SONAR emits sound waves. With LIDAR, the light is 1,000,000 times faster than the sound. An example is during a hurricane with lighting - at first, we see the lightning and only hear the sound a couple of seconds later.
Such high speed allows the device to receive data from a tremendous number of laser pulses every second. It means information is updated more frequently and, as a result, more precise data is received. An inner processor saves each reflection point of a laser and generates a 3D image of the environment. These working principles allow to create precise maps using a LIDAR installed onboard a plane, for example.
Furthermore, the same processor can calculate the distance between a detected object and a LIDAR receiver by using a simple school formula where laser pulse speed and reflection time are known, and we then calculate the distance a laser pulse travels along. This possibility found its application in the automotive industry and thrives there: all driverless cars use onboard LIDARS to scan their surroundings.
Where is LIDAR used?
At Portland State University, in the United States, they use the LIDAR system technology to check tree growth progressions in sprawling ecosystems with large surface areas. Researchers equip airplanes with these devices which give them the possibility to track the appearance of every single leaf and branch.
Using LIDAR, NASA calculated stratospheric temperature by measuring the density of atmosphere elements. In addition, the film industry also uses this technology to recreate rare or exclusive environments that are otherwise prohibited, to use for commercial and visual purposes.
The invention of this technology has had a tremendous impact on the development of the automotive industry. Self-driving and driverless cars use LIDAR to scan surroundings and plan a car’s behavior, in order to avoid collisions with obstacles.
It is easy to create fake echoes that will make the device detect existing objects further or closer than they really are using two transmitters with the same signal wavelength, which an original LIDAR has. Only one transceiver and two pulse generators can create multiple copies of LIDAR signals and send them to the receiver, which makes the device see non-existent objects.
What is RADAR?
RADAR is also known as Radio Detection and Ranging and is used to detect objects at a distance, define their speed and disposition. We are all familiar with this device as police use it in most areas to detect and regulate speeding vehicles on roads.
RADAR system technology was invented in 1940, right before World War II; however, development actually started in 1886 when one German physicist realized that radio waves could reflect from solid objects. The following describes the RADAR working principle.
How does RADAR work?
The sound echo allows us to define how far away something is using sound wave reflection from solid objects. The time it takes for sound to travel forward and backward is determined by the distance of the sound source and the surface that reflects the sound waves. At the same time, the Doppler shift of the echo allows us to define the speed of a moving object by measuring the pitch of the echo.
This principle is based on the RADAR system, with the only difference being that RADAR uses radio waves instead of sound. Radio waves can travel much further than sound and are undetectable to human sensory organs. So, the main difference between LIDAR and RADAR is that they use different signals to detect objects, though the working principle is quite the same.
Moreover, radio and light waves have the same speed - the speed of light. So, when it comes to the question of how fast data gets updated in each system (LIDAR vs RADAR systems), we have a fair draw.
How is RADAR used?
The most widespread RADAR usage is for military purposes. Airplanes, which are equipped with RADAR, can precisely measure altitude and detect other air transport devices in the vicinity. Marine RADAR systems are used in a similar way to measure the distance between other ships to prevent collisions.
This technology is also used for short-term weather forecasting to monitor wind and precipitation. Ground-penetrating RADAR is used in geology to determine the composition of Earth’s crust. Lastly, police use radar guns to monitor traffic speeds, though LIDAR has recently become more widespread in this area, due to its preciseness.
Using a radio wave receiver and a transmitter with the same wavelength an initial radar has allows to create radio noise that will make the device count the speed of a moving object as zero. That is why, when it comes to RADAR vs LIDAR self-driving car systems, both devices are deceivable and have the same security level.
Comparison of RADAR vs LIDAR
Advantages of LIDAR over RADAR
Advantages of RADAR over LIDAR
|Short wavelength lets us detect small objects. A LIDAR can build an exact 3D monochromatic image of an object. Disadvantages of LIDAR Usage Limited usage in nighttime/cloudy weather. Operating altitude is only 500-2000m. Quite an expensive technology.||RADAR can easily operate in cloudy weather conditions, and at night. Longer operating distance. Disadvantages of RADAR Usage Shorter wavelength does not allow the detection of small objects. RADAR cannot provide the user with the precise image of an object because of the longer wavelength.|
If we are to compare these two technologies separately without any background, it will be a waste of time. They have similar working principles, but each uses different kinds of waves and wave sources. RADAR uses an antenna to emit radio signals, but a LIDAR device has specialized optics and lasers for receiving and transmission.
RADARs are obviously more convenient when the detection distance is more important than the actual look of an object. For example, in the air, something large that is flying is likely an airplane, and it is important to detect it as soon as possible to avoid a collision.
On the other hand, when we are on the road, it is highly important to recognize whether an object is a pedestrian, car, or wall. This recognition will allow the system to predict the movement with onboard software and also does not focus on objects further than 500m ahead.
These qualities make a device with a light-based working principle a winner when it comes to LIDAR vs RADAR autonomous driving.