InSAR
and LIDAR
Lecture 9
Oct 30, 2007
1. Interferometric Synthetic
Aperture Radar (InSAR)

Is a process whereby radar images of the same location on the
ground are recorded by



Two antennas of one platform separated by a few meters (single pass),
or
The same radar system at different times (multi-pass or repeat-pass)
Applications on

Elevation (DEM) derivation (single or multi pass)
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

Can be as accurate as DEM from traditional optical photogrammetric
techniques. However, InSAR operate through clouds, day or night.
The first worldwide DEM (99.97%) was acquired in 2000 by SRTM in
2000, not by the photogrammetry
Surface displacement study (multi-pass only)
Examples

One SAR with 2 antennas (single-pass)

AIRSAR/TOPSAR
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Along track interferometric mode (ATI) (L and C)
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Cross track interferometric mode (TXI) (L or C)

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DEM (3-5 m or 1 m)
Shutter Radar Topographic Mission (SRTM)


Ocean current and waves
C band and X band antennas separated by 60 m
One SAR in different times (multi-pass)


SIR-C
ERS 1,2
Phase shift =
 is the fractional phase (value 0-2 radians), λ is wavelength


2
Calculate altitude
z ( y )  h    cos 
(1)
(   ) 2   2  B 2  2B cos(90     )   2  B 2  2B sin(    )

 
  (3)
2
 2
B ( )
2
(2)
2
z( y)  h 

 2 B sin(    )

 is the fractional phase (value 0-2 radians), λ is wavelength
 cos 
(4)
AIRSAR/TOPSAR


Operates from a NASA DC-8 jet. When AIRSAR is
used to create topographic map (DEM), it is called
TOPSAR.
Fully polarimetric imagery (HH, VV, HV, VH) in
three bands:
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C (5.6 cm, 5.26 GHz)
L (24 cm, 1.22 GHz)
P (60 cm, 0.45 GHz)
Spatial resolution of 10 m for 20 MHz radar data and
5 m for 40 MHz data. Multilook post-processing can
be applied to the radar imagery to reduce speckle at
the expense of decreased spatial resolution
Xie, 2002; Xie and Keller, 2006
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.
http://www2.jpl.nasa.gov/srtm/alaska.htm
Source for SRTM data

USGS gallery:

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JPL gallery:
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gahttp://srtm.usgs.gov/srtmimagegallery/index.html
http://photojournal.jpl.nasa.gov/mission/SRTM
USGS seamless distribution system (USA 30 m,
globe 90 meter)

http://seamless.usgs.gov/
SRTM coverage map
To download from here http://seamless.usgs.gov/
Displacement




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.
2. LIDAR



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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

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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
 FLI-MAP
 ALTM
 TopoEye
 ATLAS
(TerraPoint, USA)
(John Chance, USA)
(USA)
(USA)
(USA)
Lidar elevation data of Bristol, UK
http://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, followup 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
ICESat

The first LIDAR satellite for Earth launched
1/12/2003

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The Ice, Cloud, and Elevation Satellite (ICESat)
The Geoscience Laser Altimeter System (GLAS)
Two wavelengths: 532 nm and 1064 nm


532 nm channel: vertical distribution of clouds
and aerosols
1064 nm channel: surface elevation of ice sheets
and sea ice thickness, 15 cm in accuracy.
CALIPSO


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Cloud-Aerosol Lidar and Infrared Pathfinder
Satellite Observations (CALIPSO), launched
4/28/2006.
Provide a global set of data on aerosol and cloud
properties, radiative fluxes, and atmospheric state.
Equipment:

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Lidar: 632 nm and 1064 nm
Radiometer
Camera
http://www-calipso.larc.nasa.gov/
Calipso instrument
MOLA

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
Mars Orbiter Laster Altimeter (MOLA), the first
satellite-based Lidar system, launched on November
7, 1996 on board the Mars Global Surveyor.
Wavelength 1064 nm, 130 m footprint and 330 m
along track spacing (vary with latitude)
To construct a precise topographic map of Mars
S
N
Mars’ south pole has a higher elevation than the north pole by ~6 km.