For this assignment I have chosen the term Synthetic-Aperture Radar (SAR). The target audience for this
definition is non-technical distributor groups from the geo-spatial industry interested in adding SAR to
their product list. The aim of this assignment is to give distributors a basic understanding of SAR
technology, its user benefits, how it differs from other sensors, and what it’s used for. This document
includes the following three definitions: Parenthetical, Sentence and Expanded.
Synthetic-Aperture Radar (SAR)
Parenthetical definition:
Synthetic-Aperture Radar (SAR) (radar using microwaves) is an optimized form of RADAR.
Sentence Definition:
A typical radar (RAdio Detection and Ranging) measures the strength and round-trip time of the
microwave signals that are emitted by a large radar antenna and reflected off objects on the earth’s
surface. Synthetic Aperture Radar (SAR) is a signal optimization technique that achieves high resolution
imagery with antenna structures much smaller than that of the traditional Radar systems.
Expanded Definition
The following is a detailed definition of Synthetic Aperture Radar. The aim in this section is to provide a
clear and concise picture of SAR technology. This includes sections on what it is, how it differs from
other sensors, and what it’s used for.
What is SAR?
As an active sensor, Synthetic Aperture Radar (SAR) transmits microwave energy pulses to the earth. The
SAR measures the amount of energy reflected back to the satellite after it hits the earth’s surface. This
process is illustrated below in Figures 1 and 2
Figure 1
Figure 2
SAR sensors can be mounted on airborne and/or satellite platforms. They consist of a transmitter, a
receiver, an antenna, and an electronics system to process and record the data. RADARSAT-2 (graphic
below in Figure 3) is an example of a commercial Radar satellite with SAR capabilities.
Figure 3. RADARSAT-2
How does it differ from other sensors?
Unlike optical sensors, microwave energy penetrates darkness, clouds, rain, dust, or haze, enabling data
collection under any atmospheric condition. Optical data is obtained through a passive sensor that relies
on energy reflected from the earth’s surface at frequencies that can often be detected by our eyes.
Image processing techniques make it possible to combine these frequencies into a colour image of the
land surface.
Figure 4 SAR versus other Earth Observation Instruments
SAR Applications:
Because SAR is not weather dependant it is particularly useful for a number of applications that include,
flood, sea and ice monitoring, mining, oil pollution monitoring, oceanography, snow monitoring, crop
classification and disaster management. It also holds a distinct advantage over optical satellites that are
heavily limited by the climate conditions at the time of imaging.
Figure 5 is a sample SAR image courtesy of RADARSAT-1
Figure 5
Works Cited:
Canadian Space Agency. Satellites: RADARSAT-2
Y. K. Chan and V. C. Koo. AN INTRODUCTION TO SYNTHETIC APERTURE RADAR (SAR). Progress In
Electromagnetics Research B, Vol. 2, 27–60, 2008.
http://www.jpier.org/PIERB/pierb02/03.07110101.pdf
Freeman, Tony. What is Imaging Radar? National Aeronautics and Space Administration – Jet Propulsion
Laboratory. 2015. USA. http://airsar.jpl.nasa.gov/documents/genairsar/radar.html.
(Animation: http://southport.jpl.nasa.gov/html/sat_animation.html)
Natural Resources of Canada. Satellite Imagery and Products: Educational Resources – Radar Basics.
Government of Canada. 2013.
http://www.nrcan.gc.ca/earth-sciences/geomatics/satellite-imagery-air-photos/satellite-imageryproducts/educational-resources/9355
RADARSAT International (RSI).RADARSAT ILLUMINATED – Your Guide to Products and Services. July 1995.
Richmond, BC.http://spatialnews.geocomm.com/whitepapers/radarsat1.pdf