imaging radar

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Applications of Satellite Imaging Radar

M.R. Inggs and R.T. Lord

Radar Remote Sensing Group

University of Cape TownSouth Africa



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Presentation Overview

� Synthetic Aperture Radar (SAR) Applications ± On the Oceans

± On the Land

± example: SAR map of Germany

± Palaeodrainage and geological mapping

� Interferometric SAR (InSAR) Applications ± Derivation of Digital Elevation Models (DEMs)

± InSAR for earthquake mapping in South Africa

± Measuring the deflection of the earth's crust

± Recent X-SAR / SRTM mission

� Properties of Digital Elevation Models

� White Sands, New Mexico

� Drakensberg, Lesotho / South Africa



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Overview (continued)

� Along Track Scanning Radiometer (ATSR) Applications� Wind Scatterometer (WSC) Applications

± Ocean Surface Winds

� Global Ozone Monitoring Experiment (GOME)

Applications� Microwave Sounder (MWR) Applications

± Monitoring of the Antarctic Ice Cycle

� Radar Altimeter (RA) Applications



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� Coastal Zone Monitoring

± Detection of Oil Spills

� Agriculture

± Agricultural Region in the State of Washington

� Map Compiling and Updating ± Ortho-Rectified Radarsat-SAR Fine Mode Image

� Natural Disasters: Volcanoes

± Guagua Pichincha Volcano

Remote Sensing Applications in the Earth Environment



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� Natural Disasters: Earthquakes and Landslides ± Landers Earthquake

� Natural Disasters: Floods

± Flooding on the Yangtze River, China

� Natural Disasters: Hurricanes ± AVHRR Image of Hurricane Floyd

± RADARSAT Image of Hurricane Floyd

� Acknowledgements



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Synthetic Aperture Radar (SAR)

Applications



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On the Oceans

� Detecting and monitoring oil spills.� Ships can be detected and tracked from their wakes.

� Relating radar backscatter from the ocean surface to wind and current fronts,

to eddies, and to internal waves.

� In shallow waters SAR imagery allows inference of bathymetry.

� Deriving the direction of displacement of ocean waves, providing input for wave forecasting and for marine climatology.

� Regional ice monitoring. Information such as ice type and ice concentration

can be derived and open leads detected, which is essential for navigation in

ice-infested waters.



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On the Land

� The ability of SAR to penetrate cloud cover makes it particularly valuable incloudy areas such as the tropics. Image data serve to map and monitor the use

of the land, and are of gaining importance for forestry and agriculture.

� Geological or geomorphological features are enhanced in radar images thanks

to the oblique viewing of the sensor and to its ability to penetrate (to a certain

extent) the vegetation cover.

� SAR data can be used to georeference other satellite imagery to high precision,and to update thematic maps more frequently and cost-effectively, due to its

availability, independent of weather conditions.

� In the aftermath of a flood, the ability of SAR to penetrate clouds is extremely

useful. Here SAR data can help to optimize response initiatives and to assess

damages: NE RSA and Mozambique recently.

� Interferometric SAR (InSAR) can be used, under suitable conditions, to deriveelevation models or to detect small surface movements, of the order of a few

centimeters, caused by earthquakes, landslides or glacier advancement.



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SAR Map of Germany

The image shows a SAR radarmapcovering the whole of Germany.

The data used have been acquired by

the high-resolution SAR sensor

onboard the remote sensing satellite

ERS-1.

From 150 geocoded terrain corrected

scenes an image mosaic with a pixel

size of 25m has been composed,

which provides a data base for

diverse applications.



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Palaeodrainage and Geological Mapping

A number of studies have been conducted at UCT in which SIR-C and traditional optical and

infra red imaging data have been evaluated for palaeodrainage and general geological mappingin NW South Africa and Southern Namibia.

This is a SIR-C image of the

Roter Kamm meteorite

impact crater in Namibia.

Of particular interest was the

possibility of surface

penetration of the dry sand in

this region by the SIR-C

radar bands.



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Interferometric SAR (InSAR)

Applications



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Derivation of Digital Elevation Models

Tandem ERS data was used at UCT to derive a DEM of the Cape Town area. This turned into a

study of aberrations found in single antenna interferometry. The aberrations have beenattributed to atmospheric perturbations, or inconsistencies between image acquisitions.

We have also trained Indian scientists to produce DEMs for hydrological studies of remote

areas which are under development.

ERS multi-look intensity image and the flattened interferogram of the Western Cape region.



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InSAR for Earthquake Mapping in South Africa

False colour intensity

composite of two ERS

passes over the Welkom

goldfields.

Current work at UCT entails using differential InSAR to map the surface effect of a

recent earthquake in the gold fields of South Africa. This Richter magnitude 4.2 seismicevent, although possibly triggered by mining activity, occurred in a broad zone of infrequent

natural seismicity. The Welkom goldfields area shown below is not ideal for repeat pass

interferometry, since most of it is covered by active agricultural lands. The coherence is

extremely low between passes, and therefore interferometry may not be feasible at all.



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Measuring the Deflection of the Earth's Crust

185 m concrete arch Katse dam.

The filling of the Katse Dam in Lesotho has

initiated research at UCT to apply differentialInSAR to the mapping of ground deformation

induced by the loading effect of a large

reservoir.

Katse dam 3-year differential

phase with residual topography.

There are no apparent

deformation fringes.

Stereo ERS derived digital elevation

model of part of Lesotho.



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X-SAR / SRTM

Launch: 11th February 2000

Duration: 11 days

Spaceshuttle: Endeavour (STS-99)

X-SAR / SRTM is an innovative

way of collecting highly accurate

topographic information using

spaceborne radar instruments.

The collected radar images are

converted to digital elevation

models (DEMs) spanning the globe

between 60° North and 58° South. A deployable 60 m

mast carries a

second set of receiving antennas at

its tip, allowing the

very first three-

dimensional view

from space to earth.



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Properties of Digital Elevation Models

Single Pass Interferometry

X-SAR / SRTM

Repeat Pass Interferometry

ERS-Tandem

Horiz. Accuracy ca. 20m * ca. 20m *

Vert. Accuracy ca. 4m * ca. 20m *

Horiz. Sampling ** 1" x 1" lat/lon 1" x 1" lat/lon

Vert. Sampling 1m 1m

Projection Geogr. Co-ordinates Geogr. Co-ordinates

Spheroid WGS84 WGS84

Tile Size 15' x 15' lat/lon 15' x 15' lat/lon

Data Format 16 bit signed integer 16 bit signed integer

* accuracy for 66% of the data

** approximately 30m for mid-latitudes



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White Sands, New Mexico

The scene shows an area near White Sands, New Mexico, USA and covers

approximately 50 km x 150 km.

The individual phase values appear as

coloured rings. The steeper the slopes, the

closer the fringes. Topography can already

be seen directly in the interferogram.

Interferogram Radar Image



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Drakensberg, Lesotho / South Africa

The most elevated stretch of the Drakensberg, in

eastern and southern Lesotho, is composed of severely

eroded basalt capping a sandstone base. Its pinnacles

and broken and fractured blocks present a steep

eastern scarp along the length of the border between

Lesotho and KwaZulu/Natal. A steep southern scarp

lies along the length of the Lesotho-Eastern province

border.

Date: 19-Feb-2000

Scene Centre: 28° 06' East

30° 24' South

Region: Drakensberg



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Along Track Scanning Radiometer

(ATSR) Applications



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ATSR Applications

� Monitoring of agricultural fires and wildfires.

Distribution at global scale and in near real time.

All hot spots (including gas flares) with a temperature higher than 312 K

at night are precisely localised (better that 1 km).

� Volcano monitoring.

� Measuring ocean skin temperatures.



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Wind Scatterometer (WSC)

Applications



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Ocean Surface Winds

This map displays the oceansurface winds at 10m on the

28th July 2000 from the ERS-2

scatterometer.

The data was computed by

ESA and provided in their fast

delivery product data.

The current empirically

derived model function being

used by ESA to relate

normalised radar cross-section

with wind speed and direction

is referred to as CMOD4.



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Global Ozone Monitoring Experiment

(GOME) Applications



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GOME Applications

� Atmospheric ozone and NO2 global monitoring have been going on sinceGOME products became available (July 1996).

� Additional applications could stem from on-going scientific studies as GOME

data can be used also for retrieving other trace gases relevant to the ozone

chemistry as well as other atmospheric constituents and climatic variables like

clouds, aerosols and solar index, crucial for assessing climatic change.



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Microwave Sounder (MWR)

Applications



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Monitoring of the Antarctica Ice Cycle

Colours have been chosen so that the free ocean (lowest brightness

temperatures) appears in blue, whereas the sea-ice (warmest

brightness temperatures, due to its high emissivity) is in yellow.

Mapping the radiometric properties

of the ice-shelf, which has a slower

time evolution than the atmosphere

and the ocean, is a valuable input to

understand the growth, decay and

dynamics of ice sheets, which in

turn is fundamental to understand

environmental and climate changes.



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Radar Altimeter (RA)

Applications



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Radar Altimeter Applications

� Measuring the marine geoid

� Measuring sea state

� Measuring the topography of the

oceans



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Remote Sensing Applications

in theEarth Environment



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Coastal Zone Monitoring



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Detection of Oil Spills

© Canadian Space Agency, 1996

The ³Sea Empress´, a 147,000 ton supertanker, ran

aground on rocks in the south of Wales, on theevening of February 15th, 1996. Seven days later,

RADARSAT captured this image, clearly delineating

the remaining oil slick. Size, location and disperse-

ment of the oil spill can be conveniently determined

using this type of imagery. The spill appears on the

image in black tones

(A) Oil, which floats on the top of water, suppresses the ocean's capillary waves, creating a

surface smoother than the surrounding water. This smoother surface appears dark in the radar

image.

(B) The discharge from the Tywi River is keeping the immediate shore clear.

(C) The slick is extending south into the Bay.

(D) The potential impact of the oil lessens as the spill starts to emulsify (break-down) and

clean-up efforts begin to take effect.



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Agriculture



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Agricultural Region in the State of Washington


This RADARSAT image shows an

agricultural region in the State of Washington.

The circular features seen near the

bottom of the image are created by a

central pivot irrigation system. The

brighter circles could be indicating

either the presence of vegetation or an

increase in the amount of moisture in

those fields. A bit to the north, there is

an area characterized by rectangular

field patterns.

The brighter fields (A) are vegetated

while the darker (B) are bare.

To the east, a striking dendritic drainage

pattern is visible.



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Map Compiling and Updating



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RADARSAT Image: Courtesy of CSA, 1996

Ortho-Rectified Radarsat-SAR Fine Mode Image

� Main Streets in red

� Secondary Roads in blue

� City Streets in white



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Natural Disasters: Volcanoes



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Guagua Pichincha Volcano


Radarsat Image of Guagua

Pichincha Volcano near Quito,Ecuador.

Red: April 18, 1999

Green: March 25, 1999

Blue: Coherence March-April

Satellite images are revealingthe growth of a lava dome. The

appearance of such a new lava

dome is significant because

(1) it signals the presence of

new magma within the volcano

and

(2) dome growth at volcanoessuch as Guagua Pichincha is

typically accompanied by

explosive activity.



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Natural Disasters:

Earthquakes and Landslides



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Landers Earthquake

(a) Observed interferogram calculated from

ERS-1 SAR images taken before (April 24,1992) and after (June 18, 1993) the

earthquake. Each fringe in parts a, b and c

denotes 28 mm of change in range.

The asymmetry between the two sides of the

fault is due to the curvature of the fault and

the geometry of the radar. Black lines denotethe surface rupture mapped in the field. The

altitude of ambiguity is 220 m.

(b) Modeled interferogram with black lines

denoting fault patches included in the elastic

dislocation model.

(c) Residual (observed minus modeled)interferogram.

(d) Radar brightness (amplitude) image.



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Natural Disasters: Floods



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Flooding on the Yangtze River, China

This image shows flooding on the

Yangtze River, China.

The RADARSAT ScanSAR narrow

data were acquired on August 12,

1998 at 6:20 AM local time.

Scientists at the Canada Centre for

Remote Sensing geocoded,

enhanced and classified the

RADARSAT data with respect to

areas inundated by water. GIS data

were overlaid on the RADARSAT

image to provide a map reference

for normal water levels.

The resulting image displays non-

flooded areas in grey tones, normalwaters levels in dark blue, flooded

areas in light blue and the urban area

of the city of Wuhan in red.




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Natural Disasters: Hurricanes



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AVHRR Image of Hurricane Floyd

© 1999 Johns Hopkins University,

Applied Physics Laboratory

Coincident Advanced Very High Resolution

Radiometer (AVHRR) image of Hurricane

Floyd.

Date: August 29, 1999

Time: 22:22 UTC

AVHRR data is acquired with an opticalsensor at visible and infrared (reflective and

thermal) wavelengths.



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RADARSAT Image of Hurricane Floyd

RADARSAT Image of Hurricane Floyd

Date: September 15, 1999

Time: 11:08 UTC

Beam: ScanSAR Wide B




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Acknowledgements

� ESA Earth Remote Sensing Home Page: http://earth.esa.int/

� Canada Centre for Remote Sensing: http://www.ccrs.nrcan.gc.ca/

� The German Remote Sensing Data Center: http://www.dfd.dlr.de/

� The NASA/JPL Imaging Radar Home Page: http://southport.jpl.nasa.gov/

� Remote Sensing Platforms and Sensors:

http://quercus.art.man.ac.uk/rs/sat_list.cfm

� Radar Remote Sensing Group UCT Home Page: http://rrsg.ee.uct.ac.za/

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