Digital Surface Model and Digital Terrain Model

Click to enlarge - dtm 2(The Netherlands)

Height information is very important in many daily matters. For example sea level rising is one of the most threatening effects of the global warming. Therefore, monitoring of dikes becomes very essential. EUROSENSE determines the height of the earth’s surface and of the objects on it, based on airborne LIDAR measurements or aerial stereo imagery. This allows for the modelling of flood risks, production of very accurate orthophotos, volume calculations,…

Laser altimetry from aircraft or helicopter is a fast, accurate and efficient method for the acquisition of height data. Aircraft are used for the survey of large surfaces. More detailed mapping of linear elements of the earth’s surface (smaller rivers, power lines, pipelines, railway tracks or highways) are mapped in high detail operating the same equipment from helicopters. These helicopters can fly slower resulting in a higher density of measured ground points. Point densities between 1 and 100 points per square meter can be reached.

Click to enlarge - Laserdata powerlines and objects

EUROSENSE operates a LiteMapper 6800 (IGI). The rotating mirror of the system assures the regular pattern on the ground. The height measurements consist of ground points and points on objects such as buildings and vegetation. This is a digital surface model (DSM). Objects can be removed (“filtered”) from the original data resulting in a database that only contains points on the bare earth. This height model of the ground level is called a digital terrain model (DTM).

The aerial stereo imagery acquired with one of the three company owned UltraCam X(p) cameras can be used to make a DTM. The terrain extraction can be done automatically by using specific software or can be made manually. Both breaklines and mass points can be created resulting in a very detailed DTM. The accuracy of the DTM depends on the resolution and accuracy of the used digital imagery.

Click to enlarge - DTM Nederland 5

Click to enlarge - DKLN2008 (The Netherlands)Click to enlarge - DTM breaklines (The Netherlands)Click to enlarge - DTM TIN (The Netherlands)