If you’ve been following the news on self-driving cars, you may have noticed that many of the autonomous vehicle makers are using LIDAR (Light Imaging Detection And Ranging) for on-board object detection. For many autonomous automobile applications, LIDAR is a better choice than the other commonly used object-detection technology, RADAR (Radio Detection And Ranging). But when it comes to high-quality, affordable object detection that needs to stand up to rough environments, RADAR is a wise choice. Here’s why:
LIDAR sensors find objects by emitting high-frequency laser light pulses and then measuring the time (in nanoseconds) it takes for some of those pulses to strike on the object, bounce back and strike the sensor. As the object moves, a processor inside the LIDAR sensor saves information about each returned pulse and can generate an accurate 3D image of the object, where it is relative to your equipment, which direction it is moving in, and how fast it is going. A LIDAR image can be so accurate that it cannot only detect pedestrians 100 yards away but tell which direction they are facing. LIDAR has even been used to track the growth of leaves and branches to measure overall forest growth.
LIDAR has been in the news so often as media coverage of driverless cars grows, so many people mistakenly think it is a new technology. The U.S. military and NASA invented LIDAR in the 1970s, although it wasn’t “on anyone’s radar” until the 1990s, when it was (and still is) used as a geographic-mapping tool. In short, LIDAR is an extremely accurate tool for detecting the form and location of an object. It is capable of creating highly detailed images, recreating details of less than an inch on an object that is more than 100 yards away. The downside is that it is an expensive technology.
If LIDAR is the pretty pony in the pasture, RADAR is the workhorse. Invented in 1940, RADAR does not return as accurate an object image as LIDAR, but it can do it in the rain, snow, sleet, hail, fog, mud, and dust. It is also more accurate than LIDAR at night and in cloudy conditions. RADAR works similarly to LIDAR, but it emits radio waves instead of laser beams. Because laser light waves are shorter than radio waves, LIDAR can generate a more detailed image of the object. It can also detect much smaller objects than RADAR, although radio waves are more than capable of detecting humans. Both radio and light waves travel at the same speed (186,000 miles per second), so both systems refresh object-location data at the same speed.
RADAR systems cost considerably less than LIDAR systems, which typically require expensive components such as high-speed electronics, CCD receivers, optics, and motors as well as the lasers themselves. Both systems will benefit from being supported by on-board cameras, mirrors, and blind-spot detection sensors.
The point of this post is not to say that one of these object-detection technologies is better than the other. If your equipment typically operates in harsh environments such as construction sites or mines, RADAR would make more sense. Adding RADAR as a side turn assist or rear blind spot monitoring system in addition to a LIDAR system only adds another level of safety for both operators, other drivers, and vulnerable road users.