AT09.98 Applied GIS and Remote Sensing for Disaster Mitigation #6 Data Acquisition for Built Environment 9 October, 2002 Fumio YAMAZAKI yamazaki@ait.ac.th http://www.star.ait.ac.th/~yamazaki/ Course Outline (1 1. Introduction 1.1 Overview of Natural Hazards 1.2 Applications of GIS and RS to Disaster Mitigation 2. Hazard Analysis 11 Sept. 2.1 Seismic Hazard and Tsunami Hazard 18 Sept. 2.2 Volcanic Hazard 2.3 Flood Hazard Satellite data Acquisition 30 Oct. by Dr. Dutta 25Sept. by Dr. Iwao 3. GIS Data and Inventory Development 3.1 GIS Data and Digital Maps 2 Oct. 3.2 Data Acquisition for Built Environment SEC/SCE and STAR/SAT, AIT. 1 9 Oct. 2 4 Sept. Remote Sensing Technologies for Development of Urban Inventory Data Earth Observation Satellites High Resolution Satellites Aerial Photographs Scanning Laser Altimeter (LIDAR Airborne SAR Macroscopic Assessment Microscopic Assessment Vertical (a and Oblique (b Photography Vertical photography is the most common use of aerial photography for RS and mapping. 3 From Principles of Remote Sensing, ITC 4
Comparative geometry of (a map and (b a vertical aerial photograph Geometric Distortion (a Map (orthographic projection Constant scale No relief displacement (a (b (b Photo (perspective projection Varied scale Relief displacement 5 The primary geometric distortion in vertical aerial photographs is due to relief displacement. Objects directly below the center of the camera lens (i.e. at the nadir will have only their tops visible, while all other objects will appear to lean away from the center of the photo such that their tops and sides are visible. If the objects are tall or are far away from the center of the photo, the distortion and positional error will be larger. 6 Orthophotos Orthophotos: Orthographic photos which do not contain the scale, tilt, and relief distortions. Digital orthophotos are produced by transforming normal vertical aerial photos using ground control points and a Digital Terrain Model (DTM. Analog orthophotos are generated from overlapping aerial photos in a differential rectification process. Laser Scanner Laser Scanners are mounted on aircraft and use a laser beam (infrared light to measure the distance from aircraft to points located on ground. The distance measurement is combined with information on the aircraft s position to calculate the terrain elevation. Mainly used to produce detailed, high-resolution, Digital Terrain Model (DTM, and to make detailed 3D models of city buildings. 7 8
Scanning Airborne Laser (LIDAR LIDAR: Light Detection and Ranging Laser Scanning System GPS Satellite IMU Inertial Measurement Unit Measurement accuracy: 15cm Laser Altimeter Foot Print (x, y, z coordinate GPS GPS Satellite 9 Asia Air Survey Co. GPS &IMU: record accurate position and orientation of aircraft Analyzing GPS and IMU data calculates precise position (x, y, z and roll, pitch, yaw of each laser pulse returns from ground. Digital CCD camera: For stereo data extraction, digital orthophoto process 10 t L =2(R/c R: the distance between the ranging unit and the surface of the object c: the speed of light (3 x 10 8 m/sec Principle of Data Acquisition of LIDAR Use of pulses of laser light directed toward the ground and measuring the time of pulse return. A rapid pulsing: 15,000 pulses/sec 11 LIDAR pulse recording multiple returns Transmit pulse Return signal Lidar beam Modern systems can record up to five returns per pulse, which discriminates not only a forest canopy and bare ground but also surfaces in between. 12
Digital Surface Model Separation of ground and buildings may be necessary for urban modeling and damage assessment Digital Terrain Model Bird-eye View of Shin-Kobe Station Area (1m DEM obtained by LIDAR 13 Remove building Trees and others objects on the ground surface 14 Texture Mapping on Laser Image Applying the texture from an aerial photo to the reconstructed surface to make the model appear rich and realistic Airborne SAR (Synthetic Aperture Radar Active remote sensing: Transmit microwaves to the ground. Receive backscattered signals by antennas. Aerial photo Texture Mapping image Rader Platform Antenna Azimuth Direction Range Direction Texture Mapping Microwaves Laser range image Generated 3D objects View 15 By Dr. Du Jie Swath Width 16
Microwave region Longer wavelength microwave radiation can penetrate through cloud cover. This allows microwave remote sensing for all weather and all day. X-band: used extensively on airborne systems (e.g. PI-SAR for military reconnaissance and terrain mapping. C-band: common on many airborne research systems (e.g. NASA AirSAR and spaceborne systems (ERS-1, 2 and RADARSAT. L-band: used onboard SEASAT and JERS-1 satellites and airborne systems. P-band: longest radar wavelengths, used on NASA experimental airborne research system. 17 CRL/NASDA Airborne SAR High-resolution: 1.5-3.0 m All weather, Day and night Multi-frequency Observation (X-band, L-band Full-Polarimetric Observation (HH, HV, VH, VV Interferometry 18 CRL/NASDA Airborne SAR (PI-SAR X-band SAR L-band SAR Frequency 9.55 GHz 1.27 GHz Antenna size 1.05 m 0.19 m 1.55 m 0.65 m (Length Width Off-nadir look angle 10-75 degrees (Variable 20-60 degrees (fixed Observation mode 2-Ch Pol./Interfero. 4-Ch. Full-Polarimetry 6-Ch. Pol./Interfero. 1-Ch. 4-Ch. Full-Polarimetry Swath Width 19.6 / 42.5 km 8.2 / 19.6 km 4.3 / 11.9 km 42.5 km 19.6 km (Observed from 12,000m Slant range resolution 1.5 / 3 m 3/5/10/20 m Azimuth resolution (4/8 look 1.5 / 3 m 3/6 m Multi-frequency Observation X-Band L-Band L-Band Resolution 3m X-Band Resolution 1.5m SAR Antennas CRL/NASDA SAR mounted on Gulfstream II 19 Backscattering property of microwaves is dependent on their wavelength L/X composite image Purple: L-band, Green:X-band SPOT Image Panchromatic, resolution 20 10m
Polarization Polarization refers to the orientation of the electric field. Most radars are designed to transmit microwave radiation either horizontally polarized (H or vertically polarized (V. Similarly, the antenna receives either the horizontally (H or vertically (V polarized backscattered energy, and some radars can receive both. Four combinations of both transmit and receive polarizations: HH, VV: co (like-polarization HV, VH: cross-polarization Polarimetry Transmission Target Reception Co-polarization (HH Tsukuba Center X-Band 3km x 4km 21 Polarimetry is the technique to distinguish the object by the difference of the polarization. Cross-polarization (HV Composite Image Purple: HH, Green: HV 22 Airborne SAR Observation of Urban Area: Shinjyuku (Central Tokyo Polarization Ratio Images Ratio values of predominant polarized intensity Ratio value Expression Characteristics R hh HH/Q Ratio of HH polarized intensity to total polarized intensity R vh VH/Q Ratio of VH polarized intensity to total polarized intensity R vv VV/Q Ratio of VV polarized intensity to total polarized intensity Q HH VH VV HH,VH,VV : HH,VH,VV polarized intensity Color Composite Image Red:HH Green HV Blue VV (X-band, 5 km x 4 km, flight direction: right to left, illumination: top to bottom 23 R hh R vh R vv 24
Extraction of Pixels which Represent Rhh,Rvh,Rvv Color composite image showing different polarization characteristics R hh C Max(R hh in area A Comparison with Field Survey and Aerial Photographs Max(R hh Radar Max(R vv SAR Composite Intensity Image Max(R hh Max(R vh Max(R vv R vh R vv B A R R hh G R vh B R vv Max(R vh in area B Max(R vv in area C vv 25 Max(R vh SAR Composite Polarizationratio Image Aerial Photograph 1997/10 11 Nakanihon Air Service Co.,Ltd. 26 Interferometry Usu-zan Volcano, Hokkaido, Japan http://www.crl.go.jp/ck/ck521/pi-sar/j/usu-j.html X-Band SAR, VV Aerial photograph Interferometry is the function to obtain the height information using the phase difference of the signals received by two antennas. Colors represents the variations in height. The information contained in an interferogram can be used to derive topographic information and produce 3D imagery of terrain height. 27 28 Interferogram February 1999 (X-band, VV:Red, HV:Green, HH:Blue, 5 km x 5 km, flight direction: bottom to top, illumination: right to left May 30, 2000 (X-band, VV-Red, HV-Green, HH-Blue, 5 km x 5 km, flight direction: right to left, illumination: top to bottom