InSAR and LIDAR

Lecture 8

Oct 13, 2004

Interferogram of Landers earthquake 7.3 magnitude on June 18, 1992. This is a remarkable new tech gained recognition thereafter.

This is from ERS-1 Average displacement along

the fault rupture was 3-4 m, maximum was 6m.

Each color cycle represents additional 2.8 cm ground motion or displacement.

Interferometric Synthetic aperture radar (InSAR)

Elevation Surface Displacement

Principals

One SAR with 2 antennas (single-pass) AIRSAR/TOPSAR

Along track interferometric mode (ATI) (L and C) Ocean current and waves

Cross track interferometric mode (TXI) (L or C) DEM (3-5 m or 1 m)

Shutter Radar Topographic Mission (SRTM) C band and X band antennas separated by 60 m

One SAR in different times (multi-pass) SIR-C ERS 1,2

)sin(2)90cos(2)( 22222 BBBB

2

cos)sin(2

)2

()(

22

B

Bhyz

cos)( hyz (1)

(2)

(3)(4)

is the fractional phase (value 0-2 radians)

Calculate altitude

http://www2.jpl.nasa.gov/srtm/alaska.htm

Glaciers are sensitive indicators of climatic change. They can grow and thicken with increasing snowfall and/or decreased melting. Conversely, they can retreat and thin if snowfall decreases and/or atmospheric temperatures rise and cause increased melting. Landsat imaging has been an excellent tool for mapping the changing geographic extent of glaciers since 1972. The elevation measurements taken by SRTM in February 2000 now provide a near-global baseline against which future non-polar region glacial thinning or thickening can be assessed.

Source for SRTM data

USGS gallery: gahttp://srtm.usgs.gov/srtmimagegallery/index.html

JPL gallery: http://photojournal.jpl.nasa.gov/mission/SRTM

USGS seamless distribution system http://seamless.usgs.gov/

SRTM coverage map

To download from here http://seamless.usgs.gov/

Surface Displacement

Ferretti et al. 2004http://spatialdata.ees.utsa.edu/ClassWebSites/ES5053/EOS-InSAR.pdf

There is a new method called Permanent Scatterer (PS)Can determine mm-scale displacements of individidual Features. More than 15 acquisitions needed for calculation

GPS has difficultyto resolve mm./y

LIDAR LIght Detection And Ranging uses the same principle as RADAR.

The lidar instrument transmits laser out to a target. The transmitted light interacts with atmosphere and target. Some of this light is reflected / scattered back to the instrument where it is analyzed.

Use UV, visible, and infrared Transmitter (laser), receiver, and detector Distance = C x T /2 Four types

Ranger finders: it is the simplest lidars, it measures the distance, then create the topographic map

DIAL: Differential Absorption Lidar is used to measure chemical concentrations (such as ozone, water vapor, pollutants) in the atmosphere.

Doppler Lidars: it’s used to measure the velocity of a target Raman LIDAR: can measure gaseous species

Airborne Lidar System

ALTMS (TerraPoint, USA) FLI-MAP (John Chance, USA) ALTM (USA) TopoEye (USA) ATLAS (USA)

Lidar elevation data of Bristol, UKhttp://www.npagroup.co.uk/engenv/engineering/lidar_img1.htm

These data are collected with aircraft-mounted lasers capable of recording elevation measurements at a rate of 2,000 to 5,000 pulses per second and have a vertical precision of 15 centimeters (6 inches). After a baseline data set has been created, follow-up flights can be used to detect shoreline changes.

Surface and DTM

http://www.gisdevelopment.net/technology/rs/ma03234a.htm

DSM and DTM

DSM DTM (bare)

Airborne Lidar

http://www.etl.noaa.gov/et2/data/data_pages/texaqs/air_aerosol.html

DIAL laser measures water vapor, clouds, and aerosols by comparing the absorption and scattering of different laser pulses on these atmospheric species

http://oea.larc.nasa.gov/PAIS/LASE.html

CALIPSO

Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations, to be launched 2005.

Will provide a global set of data on aerosol and cloud properties, radiative fluxes, and atmospheric state.

Equipment: Lidar: 632 nm and 1064 nm Radiometer Camera

http://www-calipso.larc.nasa.gov/

Calipso instrument

Midterm review