LiDAR
Just as cameras allow us to see objects in pictures, a LiDAR instrument allows us to visualise objects in three dimensions.
A LiDAR system can be carried on an aircraft to look down on the ground or moved around at ground level to draw objects around it. It can also be used on a road vehicle. Large areas can be covered quickly using these mobile lidar mapping techniques.
LiDAR is an acronym that stands for "Light Detection and Ranging"
At the heart of a LiDAR system is a laser ranger. The laser is made to send out a small pulse of light and then to receive the reflected pulse, once it has hit an object. The time measured between the pulse being sent and subsequently received can then be equated to the distance travelled by the pulse, because the speed of light is constant.To produce a three dimensional model of an area, the laser is scanned across and along the area of interest and many pulses are used to produce point distances on the ground, from the laser. The angle of the laser and its position is recorded for each laser pulse it sends out and thus a three dimensional image can be produced by combining the point distances relative to each other in a computer program. The closer the points are on the ground, the more accurate the model.
Modern LiDAR systems can produce hundreds of thousands of pulses every second and can be flown several thousands of feet above the earth. This allows for extremely rapid acquisition of data over large areas, which may be hostile or inaccessible from the ground using previous methods of surveying.
Airborne LiDAR
When fitted to an aircraft, the system is flown over an area along overlapping strips until the complete area of interest is covered by the laser points.The use of high accuracy GPS positioning and inertial attitude measuring instruments, together with powerful computing software allow very accurate models to be produced. The picture above shows colour contour map type data of the River Thames.
Applications of LiDAR
Applications for the use of LiDAR are evolving, but generally any application that requires a volumetric or three dimensional set of data can be considered. Below are just a few examples of how LiDAR data is used currently.- Urban planning
- Floodplain mapping
- Coal stock monitoring
- Quarry extraction monitoring
- Road/rail planning
- Coastal erosion monitoring
- Telecommunication cell network planning
LiDAR Products
Data from the LiDAR can be used in a variety of ways:- Computer file containing XYZ data (position and height)
- Hard copy print of colour contour map
- 3D representation on a computer, allowing rotation and ‘fly-throughs’
- Physical scale models
Our suite of instruments includes:
- A Leica RC20/30 full format film camera
- An Optech GEMINI LIDAR system integrated with a Rollei digital camera
- An Optech ALTM 2033 LIDAR system
- A Leica ADS40 camera
- A Vexcel UCX large format digital camera
- A Specim AISA Eagle multi-spectral line scanner
- A Track’Air MIDAS oblique photography system
