Surveying Using data recorders coupled with total stations
- Slides: 7
Surveying Using data recorders coupled with total stations u Advantages u m High accuracy DTM Accurate data Ø Data adapted to the character of the terrain Ø u Disadvantages m Time consuming Applied to specific and small projects Ø To complement photogrammetric data capture Ø 1
Laser scanning Introduced in the beginning of nineties u Acquire dense and accurate elevation data u m. Distance measured by pulse ranging or multi-frequency sidetone phase m. With the help of DGPS and INS the position and direction of aircraft (origin of measured distance) is determined m. Point positions first obtained in eg WGS 84; then is converted to a local reference system u Used in DEM and 3 D city model production 2
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) resampling (of the DTM) Topo. Sys 3
Examples: Monitoring open pit mines by LIDAR DSM Closed open pit Döbern, Germany DTM area: 2 km² by 2 km² 4
Example of DSM from LIDAR Part of city of Lisbon, Portugal 1 m raster DSM, area about 1 km² © Edinfor
Example of DSM from LIDAR © Vermessungsamt Mannheim City of Mannheim, Germany 1 m raster DSM, area about 1 km² 7
Laser scanning as compared with photogrammetry The possibility to penetrate vegetation u Capability of measuring ground points beneath the canopy u The capability to capture data at night or at low sun angles u Can be used easily in textureless areas u Can result in 0. 1 to 0. 2 m accuracy u Not many companies offer the technology u Difficult to compare results u 8
