1. Surveying Using data recorders coupled with total stations Advantages
High accuracy DTM
Accurate data
Data adapted to the character of the terrain
Disadvantages
Time consuming
Applied to specific and small projects
To complement photogrammetric data capture

2. Laser scanning Introduced in the beginning of nineties
Acquire dense and accurate elevation data
Distance measured by pulse ranging or multi-frequency sidetone phase
With the help of DGPS and INS the position and direction of aircraft (origin of measured distance) is determined
Point positions first obtained in eg WGS84; then is converted to a local reference system
Used in DEM and 3D city model production

3. Laser Scanning PRODUCTION
calibration (tuning of 3 different sub-systems)
flight with GPS navigation
interpolation and transformation
(of 3 data sets)
filtering (of terrain profiles)
TopoSys
resampling (of the DTM)

4. Examples: Monitoring open pit mines by LIDAR
DSM
DTM
Closed open pit Döbern, Germany area: 2 km² by 2 km²

5. Example of DTM from LIDAR
River Estuary, North Sea, Netherlands

6. Example of DSM from LIDAR
Part of city of Lisbon, Portugal
1 m raster DSM,
area about 1 km²
© Edinfor

7. Example of DSM from LIDAR
© Vermessungsamt Mannheim
City of Mannheim, Germany
1 m raster DSM,
area about 1 km²

8. Laser scanning as compared with photogrammetry
The possibility to penetrate vegetation
Capability of measuring ground points beneath the canopy
The capability to capture data at night or at low sun angles
Can be used easily in textureless areas
Can result in 0.1 to 0.2m accuracy
Not many companies offer the technology
Difficult to compare results