Everything You Need to Know About Lidar
What is Lidar?
Lidar stands for Light Detection and Ranging and is a popular remote sensing method used to measure the exact distance from an object using light from a pulsed laser. Popularized in the 1980s after the arrival of commercially available Global Positioning Systems (GPS), lidar sensing was performed in surveying using planes to measure variable distances to the earth's surface and create accurate 3D information.
There are three main components to a LiDAR — the scanner, laser, and GPS receiver. These components together are used in surveying to determine land management, planning efforts, hazard assessment. Lidars are generally used to map the structure and shape of the Earth's surface, but modern advancements allow for everyday use, such as in Apple's
Types of Lidar
There are two types of Lidar Systems according to Geospatial World — Airborne and Terrestrial.
Airborne Lidars are attached to drones or planes which measure the exact distance to an object by bouncing a laser while Terrestrial Lidars go on vehicles or tripods to measure data points.
Moreover, Topographic lidar uses an infrared laser to map land surfaces, while bathymetric lidar uses green light to penetrate water and measure seafloor and riverbed elevations.
Lidar vs Radar
The main difference between Lidars and Radars is that Radars use radiowaves while Lidars use lasers. Lidar sensors detect light that bounces off a surface to measure distance. Radars use electromagnetic energy to measure distance.
Lidar’s versatility and accuracy allows it to be utilized in a multitude of practices such as archaeology and oceanography but it is commercially used by geoscientists and engineers for city planning, agriculture and architecture.
How LiDAR’s algorithm works:
1. Laser signals are emitted
2. Laser signals reach an obstacle
3. Signal reflects from the obstacle
4. Signal returns to the receiver
5. and then a laser pulse is registered
With LiDAR, light travels 1x106 times faster than sound, allowing a receiver to get data every second from a huge number of laser pulses. Information is updated more frequently; therefore, more precise data is received. An inner processor saves each laser reflection point and creates a 3D image of the area. At a distance of 100 meters, LIDAR systems have a resolution of a few centimetres.
LiDAR is a lightweight solution that allows 3d mapping to be accurate at a high level. It is used for laser altimetry and contour mapping. It is also used to create a digital elevation model (DEM) or a digital terrain model (DTM) for 3D mapping in Geographical Information Systems (GIS).
RADAR (Radio Detection and Ranging)
Instead of a laser, RADAR uses radio waves but operates in almost the same way as that of LiDAR.
The antenna of the RADAR instrument doubles as both a radar receiver and a transmitter. Using sound wave reflection from solid objects, the sound echo determines the distance from obstacles. The relative speed or velocity of a moving object can also be determined accurately using the Doppler shift of the echo which is done by measuring the pitch of the echo. Upon interaction with objects, radio waves have less absorption compared to light waves, so they can operate over a relatively long distance.
RADAR can detect objects at long distances and through fog or clouds, but the size of the antenna limits its lateral resolution. At a distance of 100 meters, the resolution of regular RADAR is several meters.
The most common use of RADAR technology is for military purposes.
To measure altitude and track other transport devices and objects in the vicinity, airplanes and battleships are also fitted with RADAR. In certain cases, the police often use RADAR technology to track and control speeding vehicles on highways.
LiDAR vs RADAR
For more information about Lidars or surveying services in the Philippines, check out FilGeo Solutions.