|
Airborne Laser Scanning – Cost effective spatial data
The return signal strength of each of the first and last returns is also recorded. This information can be used with a grayscale to create geo-referenced images. The image below shows ground and non ground returns.
Airborne Laser Scanning is an active remote sensing technology. The system emits laser signals and as such can be operated at any time during the day or night. Applications ALS in Forestry Because of its ability pass between tree branches to record both ground and non ground features, ALS is particularly suited to forestry applications. Applications include the acquisition of data to compute average tree heights, the use of terrain data to plan the location of roads to be used in timber harvesting and the determination of drainage locations for the design of retention corridors. The diagrams below show contours derived from ground data, which clearly indicate drainage locations, together with a profile showing ground and tree canopy. 
Flood Plain Definition Because of the ability of Airborne Laser Scanning to observe large terrain areas accurately and quickly, flood plain mapping is a frequent application. As an example, an area 30 km by 10 km can be captured, using a fixed wing survey platform, in about four hours. The vertical accuracy of the data would be around 15 cm and the average point spacing would be 1.5 metres. About 153,000,000 data points would be recorded, providing a detailed description of the terrain and objects on it. |