Airborne Laserscanning Technology for Natural Hazard Monitoring and Protection in Alpine Areas

Transcription

1 Member of Swissphoto Group Airborne Laserscanning Technology for Natural Hazard Monitoring and Protection in Alpine Areas Geomorphometry 2009, Zürich September 1 st 2009 Stephan Landtwing BSF Swissphoto AG

2 Presentation Outline BSF Swissphoto (short) Company Presentation Lidar Technology and Processes Digital Elevation Models in Switzerland Project LWN country-wide Lidar data collection Lidar Data for Natural Hazard Monitoring and Protection Project Examples Handheld Lidar System scan2map Conclusions and Outlook

3 BSF Swissphoto Core business Airborne Data Acquisition 3D Mapping Geodesy & Surveying 3 offices Zürich-Regensdorf, Switzerland Berlin-Schönefeld, Germany Pasewalk, Germany 60 employees Turn-over 9 Mio in 2008 ~ 50 % in Switzerland & Germany ~ 30 % in Austria, Italy, Poland, Ukraine ~ 20 % other areas

4 3D Mapping: Technology and Resources aircraft 3 Large-format Digital Cameras Vexcel Ultracam (D, X, Xp) 2 Optech Lidar Systems ALTM 3100, ALTM Gemini 1 handheld Lidar System Scan2Map 3 Analogue Cameras > 10 digital photogrammetric workstations

5 Lidar Technology The Basics D-GNSS: Positioning IMU (Inertial Measurement Unit): Orientation Lidar: Time-of-Flight measurement Camera & other sensors optional D-GNSS Elevation Yaw Longitude Pitch Latitude Roll IMU

6 Lidar Technology The Pros Active system: Independent of ambient lighting Direct geo-referencing Multiple measurements per emitted pulse Direct determination of surface model (DSM) Penetration of forest to derive terrain model (DTM) High level of detail to derive further objects

7 Lidar Technology Forest Penetration

8 Lidar Technology The Hardware GPS Antenna GPS Antenna (Base Station) LIDAR & Digital camera

9 Lidar the Workflow Flight Planning GNSS Reference Station Survey Flight GNSS/IMU, Point Cloud Processing Georef. 3D Point Cloud unclassified Automatic Classification ( 95% ) - Ground - Outliers - others (Vegetation, Buildings, Vehicles, Power Lines,...) - (Buildings) Manual Checks & Corrections - DTM Corrections - Building Details - Catenaries & Towers Automatic & Semiaut. Classification Ground Control Classified Point Cloud DTM, DSM Q Docs, Metadata

10 Lidar Workflow Flight Planning

11 Flight Planning Terrain

12 Flight Planning Terrain

13 Flight Planning Terrain

14 The Survey Flight

15 Lidar Workflow - Post Processing GNSS/IMU Processing Trajectory Point Cloud Computation Boresight Calibration and Strip Adjustment Coordinate Transformations Tiling Classification

16 Lidar Derived Products Base Data Derived Products and Applications Terrain Model Surface Model Contours Shading Analysis Cadastre Data Noise Propagation Plans Models and Maps Hillshades Flood Models Orthophotos 3D Building Models 3D-Visualization Plans Viewshed and Analysis Maps

17 Digital Elevation Models in Switzerland Global Models: GTOPO-30, SRTM, ASTER etc. Outstanding Topographic Maps 1: DHM25: 25 m Grid Model based on Digitized Contours (10 m, 20 m) Lidar DTM/DSM collected in 6 lots > km 2

18 Project LWN country-wide Lidar DTM/DSM Product Specifications DTM and DSM Vertical accuracy of interpolated model < 0.5 m (1 ) Point density open area : 0.44 pts/m2, maximum distance between two points: 2 m Areas above 2100 m MSL not part of the project DTM: Point density forested area: 1370 pts/ha DSM: Vertical accuracy < 1.5 m (1 ) for vegetation Point cloud filtering DTM defined as topsoil without vegetation and buildings Non-permanent objects like trains, non-perennial vegetation and installations for constructions to be removed from DSM DSM classified as Ground, Vegetation and Building

19 Swiss Topography Plains Moderate Hills Rolling hills Steep hills and mountains Lakes

20 Challenging Flight Planning & Operations Sensors employed by BSF Swissphoto in the project: TerraPoint ALTMS2536 (lot 2 lot 4) Optech ALTM3100 (lot 5) Flying Height ft AGL, side overlap % Example flight plan in the Canton Uri Main Valley from 500m ascending to 900 m Steep slopes perpendicular to main valley: within 3.5 km +/ m height differences (~55 degree) Discontinuous pattern of mountains and ridges

21 Planned flight lines Planned linesand over main valley as 3D profile Topographic Map 1: Trajectory flight line profile merged

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23 Lidar for Natural Hazard Monitoring and Protection Project Example 1: Natural Hazard Map Canton St. Gallen Mandatory inventory of areas at risk by natural hazards: Flooding, avalanches, rock falls, land slides,... Resulting risk zones have consequences for land use planning Detailed hazard simulation and analysis on the basis of highresolution vector elevation models Blickrichtung der Foto vom

24 Lidar for Natural Hazard Monitoring and Protection Project Example 1: Natural Hazard Map Canton St. Gallen Project Area 330 km 2 DTM/DSM production Pre-Alpine and Alpine territory ( m MSL) in Eastern Switzerland Ca. 30% urban area DTM Production Concept Data collection Airborne Laserscanner Optech ALTM 3100 Mean point density = 2 pts / m 2 Digital Aerial Camera Vexcel UltraCamX GSD = 12 cm Terrestrial survey of ground control elements DTM generation based on Classified and thinned Lidar point cloud (TIN) 2700 oriented aerial images stereo compilation of break lines and obstacles Existing 2D cadaster data from 61 counties

25 Natural Hazard Map Canton St. Gallen Data Examples Lidar Base Data DSM, Digital Surface Model DTM, Digitales Terrain Model

26 Natural Hazard Map Canton St. Gallen Data Examples Automatically derived forest boundaries (increased roughness)

27 Natural Hazard Map Canton St. Gallen Data Examples Combination Lidar + breaklines DTM as TIN Hillshade and vector data

28 Natural Hazard Map Canton St. Gallen Data Examples Enforced Breaklines for correct drainage simulation Lidar DTM w/o breaklines Final DTM w/ enforced breaklines

29 Natural Hazard Map Canton St. Gallen Data Examples 3D Visualization with extruded buildings, bridges etc.

30 Lidar for Natural Hazard Monitoring and Protection Project Example 2: Rock Fall on Highway Rock fall on Trans-Alpine Gotthard highway May 31st 2006

31 Lidar for Natural Hazard Monitoring and Protection Project Example 2: Rock Fall on Highway Rock fall on Trans-Alpine Gotthard highway May 31st 2006 Immediate Lidar data collection for Documenting the situation Identifying future hazards Planning protective measures

32 DSM incl. vegetation and buildings DTM

33 Highway Rock Fall Data Examples Overhanging rock face contour generation

34 Highway Rock Fall Data Examples Overhanging rock face contour generation 5m

35 Highway Rock Fall Data Examples Overhanging rock face contour generation 1m

36 Highway Rock Fall Data Examples Overhanging rock face contour generation 50cm

37 Highway Rock Fall Data Examples Overhanging rock face contour generation 25cm

38 Highway Rock Fall Resulting Protection Measures

39 Lidar for Natural Hazard Monitoring and Protection Project Example 3: Land Slide Monitoring Thawing permafrost leads to instable slopes and landslides Annual Lidar flight over several affected areas in Tyrolia, Austria to detect and document terrain changes

40 Handheld Lidar & Camera System scan2map

41 scan2map - Advantages Simple installation on a helicopter very little installation time (< 30min) Fast deployment on short notice No recalibration needed: all sensors (incl. GNSS antenna) are tightly fixed in one sensor block Oblique and nadir surveying can be performed in a single flight Map vertical rock faces with high accuracy Fills the gap between terrestrial and conventional airborne Lidar

42 scan2map Data example Colorized point cloud of quarry

43 Conclusions and Outlook Technology Hardware Mature commercial systems, robust operation Multi Pulse in Air technology available, operation tricky Full Wave Form recording offered by most vendors Development to higher pulse rates and accuracies expected to continue Technology Software and Algorithms Lagging behind capabilities of hardware R & D focus on: Calibration / Strip adjustment Classification Automated (vector) feature extraction Full Wave Form analysis Tying point cloud data into consumer GIS software

44 Conclusions and Outlook Applications Many countries working on wide-area DTM/DSM collection (1 4 points / m 2 ) Many potential clients are only beginning to see the advantages of Lidar technology: Corridor infrastructure: power lines, pipeline, railway, highway Natural hazards, emergency response Forestry Industry Trends Sensor Fusion Real-time QC and georeferencing Using point cloud data in GIS environments

45 Thank you for your Attention! Questions?