What is Lidar?

Lidar Fact Sheet

Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance. Different devices, or sensors, are used to detect and monitor:

Multispectral camera: consists of >3 bands with each band at a different location of the electromagnetic spectrum. Often collected using Red, Green, Blue (True Color) or Near-Infrared, Red, Green (False Color Infrared) and used for simple mapping projects.

Hyperspectral camera: consists of > 60 bands with each band at a different location of the electromagnetic spectrum. Hyperspectral imagery is used to differentiate between vegetation species, geologic minerals, and other applications by looking for differences in each objects spectral signature.

Thermal camera: consists of camera capable of collecting bands in the infrared range of the electromagnetic spectrum. Thermal imagery is used to look for heat signatures such as animals or for energy budgets (i.e poor insulation). Thermal imagery is typically collected at night to mitigate the effects of the sun.

Radar: Does not use the passive energy from the sun, but actively emits energy in the form of long wavelengths and records the returned energy. Generally the harder the surface the more energy is returned to the sensor. There are many types of radar sensors each capable of sending and receiving long wavelengths. Different wavelengths interact with the earth’s surface differently. The different wavelengths are used to detect soil moisture, vegetation density, or to detect snow densities

Lidar: Does not use the passive energy from the sun, but actively emits concentrated short wavelength energy and records the amount of energy returned and the time it took to return. Because the time is recorded, the speed of light is known, and the sensors location is known, the distance from the sensor can be calculated, yielding high resolution 3D information. Lidar is used to create high resolution models of objects, vegetation characteristics, and the earth surface.

Sensors can be mounted on different platforms. Platforms include satellites, airplanes, UAVs, or the ground. There are trade-offs to each platform. Satellites generally cover large areas, are less expensive, return to the same spot between 1- 18 days, and don’t show as much detail on the ground. Airplanes generally cover moderately large areas, are more expensive, can be collected any time safe to fly, and show more detail on the ground. UAVs generally cover small areas, are moderately expensive, can be collected when possible, and show high ground detail. Ground collection covers very small areas, is less expensive, can be collected when possible, and shows high ground detail, but at an oblique angle.

Knowing how and if remote sensing can be used for a particular project can be difficult, but when done correctly, remote sensing is a cost effective approach to a large variety of monitoring/mapping projects.