We often post LIDAR images (mainly on our Facebook page) to highlight finds or points of interest within the terrain. LIDAR images certainly do help highlight evidence of land disturbance or possible structures.
LIDAR stands for LIght Detection And Ranging. In its most simplified form it works much like a sonar system on a submarine. A sound is emitted from the system, it them waits for its return and can use the time delay to calculate the distance. (Distance = Speed * Time / 2)
In the case of LIDAR a pulse of light is pointed at the surface, the return is the reflection of light being bounced back. The time factor is used to calculate the distance.
In modern LIDAR devices there is generally a lot more data involved. The device will know its exact location is space due to its GPS system. It will also use extremely accurate measurements to work out its pitch and roll angle. By knowing exactly where it is, its inclination and roll angle it can work out precisely where the light will strike he surface. It can then generate a data point.
Each unique data point will refer to one specific point on the ground. The data will include its GPS position and height. The points can then be combined to form what is known as a “point cloud” A point cloud forms the basis of a 3D model of the surface.
Today most LIDAR surveys are carried out from Aircraft. They will operate along a predetermined route and at the optimal altitude to get the best results. The advantage of using aircraft is they can cover vast areas in an acceptable timescale.
It is also possible to carry out smaller surveys using Unmanned Aerial Vehicles (Drones). The advantages of using UAV’s to conduct LIDAR surveys are cost and the ability to operate safely at much lower altitudes.
Generally speaking large scale surveys will be carried out using aircraft. Smaller more focused surveys are often carried out using UAVs.
LIDAR has proven to be a very useful tool for us as we try and find out more about the history of the local area. We currently make use of LIDAR data that is provided by the Scottish Government. We are also exploring the possibility of carrying out our own LIDAR surveys on a small scale. This will be a project for the future and we will certainly keep you updated on this.
For now, LIDAR is one of the many tools we have at our disposal and we are very thankful to have access to it.