Figure 11: An example of an interferometric SAR
image display with the magnitude component (left)
and the phase component (right). (SAR image was
produced by the CCRS C/X Airborne SAR, courtesy
of CCRS, NRCan, Canada.)
response as well as a contour plot, a range profile plot,
and an azimuth profile plot. These plots are useful
for qualitative evaluation of the imagery. In addition,
quantitative measurements calculated include the -3dB
impulse response (IRW) widths in range and azimuth,
integrated sidelobe ratio (ISLR), and peak to sidelobe
ratios (PSL). The equivalent number of looks in an
image is measured by windowing a uniform area in the
image such as a field and comparing the mean and vari-
ance statistics for this windowed area. Examples of the
point target analysis plots are given in Figure 12.
4.3 Map Projections
Most SAR imagery is produced in the ground range-
azimuth coordinates. This coordinate system is con-
venient for SAR image production at the ground sta-
tion, but less so for the interpreter. Thus in addi-
tion to geocoding, it is possible to reproject an image
into a standard map projection such Lambert Con-
formal Conic (LCC), Universal Transverse Mercator
(UTM), or Universal Polar Stereographic (UPS). Once
projected, the image may be displayed with full lati-
tude/longitude tagging, pixel value read-off, zoom and
pan.
9. POLARIMETRY
Conventional SAR systems transmit and receive
electromagnetic waves of a fixed, single polarization.
PKANAL - Interpolated Data POWER Value
ZEHION - A DI 2170-4
TINE - à
1 March 1994
Tints Ao
13:20
Hm
LIMES « 99 - 430)
PIMEURC 113 - 146)
Spacing: 1 wn
^7 Soacing- 1
--PEOK LOCAEION--..—
Mmm
Perna > 131 n
AZIMUIH > 21 px
aire > 115.55
“INTENPOLAIED sPACE-
fpacine- 0.23 n
MEAN | = 7.2052460+007
STDEU = 23.112403e:008
--PEAK LOCATION
ANtOE.. > 65 px
AZIMUTH > 67 ox
Pk.Mey.= 3.78433e+009
+. (08)= 93,78
AN 308 Hid 3.0190 n
AZ 308 Mid 3.0308 4
MENSIMED-INTEO
MAIN Lob.= 119
‚PH. -
. 65
SIDE Lobe: 114.32
13.0 = -5.501
—{s{nO0/x)002-1PU,-
MAIN Lob.= 119.04
SIDE Lobs= 115.94
1368 = -3.0992
RANDE .. PIXEL DIRECTION AZIMUTH LINE DIRECTION
Figure 12: Example output produced by the point
target analysis functions.
Polarimetric SAR systems transmit two electromag-
netic waves of orthogonal polarization (commonly hor-
izontal and vertical) and measure the orthogonal com-
ponents of each reflected wave. These four measure-
ments can lead to the determination of the scattering
matrix for each return cell in a SAR scene. The re-
flected waves from many surface features have strong
dependencies on the polarization of the incident wave.
The additional information provided by polarimetric
SAR can be used to improve identification and classi-
fication of features in SAR imagery.
9.1 Image Synthesis
Through proper calibration, the four polarimetric mea-
surements can be used to derive the scattering matrix
for each pixel in a SAR scene. Thus for an antenna
transmitting an arbitrarily polarized wave, the polar-
ization of the reflected wave can be determined from
the scattering matrix. Finally, given an arbitrarily po-
larized receive antenna orientation the expected SAR
system measurement can be calculated. Performing
this calculation for an entire SAR scene results in image
synthesis. EV-SAR provides an interactive function
for synthesizing images given theoretical SAR systems
having arbitrary transmit and receive antenna orienta-
tions. Both the receive and transmit orientations can
be independently specified and incremented, allowing
for an animated sequence of synthesized images.
9.2 Polarization Signatures
A useful tool for analyzing and interpreting polarimet-
304
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