ISO/TS 19159-3:2018

TECHNICAL ISO/TS
SPECIFICATION 19159-3
First edition
2018-05
Geographic information — Calibration
and validation of remote sensing
imagery sensors and data —
Part 3:
SAR/InSAR
Information géographique — Calibration et validation de capteurs de
télédétection —
Partie 3: SAR/InSAR
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, abbreviated terms and conventions . 8
4.1 Symbols . 8
4.2 Abbreviated terms .10
4.3 Conventions .10
5 Conformance .11
6 General SAR sensor calibration model .11
6.1 Introduction .11
6.2 Top-level model .12
6.3 Radar system .14
6.4 Antenna system .15
6.5 Antenna phase centre .16
6.6 SAR signal processing .17
6.7 Atmospheric propagation and earth motion .18
6.8 SAR calibration field .20
6.8.1 Introduction .20
6.8.2 CA_SARCalibrationField .22
6.8.3 CA_SARCalibrationNaturalField .22
6.8.4 CA_SARCalibrationManmadeField .22
6.8.5 CA_SARCalibrationEquipment .22
6.8.6 CA_CornerReflectorAndTransponder .22
6.8.7 CA_GroundReceiver .23
6.8.8 CA_ScatteringMatrix .23
6.9 SAR validation .23
6.10 SAR Requirement .24
7 InSAR sensor calibration model .24
7.1 General .24
7.2 CA_InSARSensor.25
7.3 InSAR Requirement .27
8 PolSAR sensor calibration model .27
8.1 General .27
8.2 CA_PolSARSensor .28
8.3 PolSAR requirement .29
Annex A (normative) Abstract test suite .30
Annex B (normative) Data dictionary .31
Annex C (informative) SAR geometric calibration use case .46
Annex D (informative) SAR radiometric calibration use case .50
Bibliography .53
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
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on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
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For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 211, Geographic information/Geomatics.
A list of all parts in the ISO 19159 series can be found on the ISO website.
iv © ISO 2018 – All rights reserved

Introduction
Imaging sensors are one of the major data sources for geographic information.
The image data captures spatial and spectral measurements and has numerous applications ranging
from road/town planning to geological mapping. Typical spatial outcomes of the production process
are vector maps, digital elevation models, and 3-dimensional city models.
In each case the quality of the end products fully depends on the quality of the measuring instruments
that have originally sensed the data. The quality of measuring instruments is determined and
documented by calibration.
Calibration is often a costly and time consuming process. Therefore, a number of different strategies
are in place that combine longer time intervals between subsequent calibrations with simplified
intermediate calibration procedures that bridge the time gap and still guarantee a traceable level of
quality.
This document standardizes the calibration of remote sensing imagery sensors and the validation of the
calibration information and procedures. It does not address the validation of the data and the derived
products.
Many types of imagery sensors exist for remote sensing tasks. Apart from the different technologies the
need for a standardization of the various sensor types has a different priority. In order to meet those
requirements ISO/TS 19159 has been split into several parts. ISO/TS 19159-1 addresses the optical
sensors. ISO/TS 19159-2 addresses the airborne lidar (light detection and ranging) sensors. ISO/
TS 19159-3 (this document) covers synthetic aperture radar (SAR) and interferometric SAR (InSAR).
TECHNICAL SPECIFICATION ISO/TS 19159-3:2018(E)
Geographic information — Calibration and validation of
remote sensing imagery sensors and data —
Part 3:
SAR/InSAR
1 Scope
This document defines the calibration of SAR/InSAR sensors and validation of SAR/InSAR calibration
information.
This document addresses earth based remote sensing. The specified sensors include airborne and
spaceborne SAR/InSAR sensors.
This document also addresses the metadata related to calibration and validation.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 19103, Geographic information — Conceptual schema language
ISO/TS 19130:2010, Geographic information — Imagery sensor models for geopositioning
ISO/TS 19130-2:2014, Geographic information — Imagery sensor models for geopositioning — Part 2: SAR,
InSAR, lidar and sonar
ISO 19157, Geographic information — Data quality
ISO/TS 19159-1:2014, Geographic information — Calibration and validation of remote sensing imagery
sensors and data — Part 1: Optical sensors
ISO/TS 19159-2, Geographic information — Calibration and validation of remote sensing imagery
sensors — Part 2: Lidar
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http: //www .electropedia .org/
— ISO Online browsing platform: available at http: //www .iso .org/obp
3.1
accuracy
closeness of agreement between a test result or measurement result and the true value
Note 1 to entry: In this document, the true value can be a reference value that is accepted as true.
[SOURCE: ISO 3534-2:2006, 3.3.1, modified — NOTES 1, 2 and 3 have been deleted. New Note 1 to entry
has been added.]
3.2
antenna pattern
ratio of the electronic-field strength radiated in the direction θ to that radiated in the beam-maximum
direction
3.3
aperture reference point
ARP
3D location of the centre of the synthetic aperture
Note 1 to entry: It is usually expressed in ECEF coordinates in metres.
[SOURCE: ISO/TS 19130:2010, 4.4]
3.4
attitude
orientation of a body, described by the angles between the axes of that body’s coordinate system and
the axes of an external coordinate system
[SOURCE: ISO 19116:2004 4.2]
3.5
azimuth resolution
resolution in the cross-range direction
Note 1 to entry: This is usually measured in terms of the impulse response of the SAR sensor and processing
system. It is a function of the size of the synthetic aperture, or alternatively the dwell time (e.g. larger
aperture → longer dwell time → better resolution).
Note 2 to entry: 3 dB width of the impulse response is the normal value of measurements.
Note 3 to entry: Cross-range direction is also the same as along-track direction.
[SOURCE: ISO/TS 19130:2010, 4.7, modified — Notes 2 and 3 to entry have been added.]
3.6
backscattering coefficient
average radar cross section per unit area
Note 1 to entry: If the radar return from the illuminated area is contributed by a number of independent
scattering elements, it is described by the backscattering coefficient instead of radar cross section used for the
point target. It is calculated as:
σ
σ =
A
where
σ is the total radar cross section of an area A;
σ is a dimensionless parameter and is usually expressed in decibels (dB) as follows:
0 0
σσ=10log
dB 10
Note 2 to entry: “Backscattering coefficient” is sometimes called “normalized radar cross section”.
2 © ISO 2018 – All rights reserved

3.7
calibration
process of quantitatively defining a system’s responses to known, controlled signal inputs
[SOURCE: ISO/TS 19101-2: 2008, 4.2]
3.8
calibration coefficient
ratio of SAR image pixel power to radar cross section without considering additive noise, after the
processor gain is normalized to one, and elevation antenna pattern, range and atmospheric attenuation
are all corrected
3.9
correction
compensation for an estimated systematic effect
Note 1 to entry: See ISO/IEC Guide 98-3:2008, 3.2.3, for an explanation of “systematic effect”.
Note 2 to entry: The compensation can take different forms, such as an addend or a factor, or can be deduced
from a table.
[SOURCE: ISO/IEC Guide 99:2007, 2.53]
3.10
cross-talk
any signal or circuit unintentionally affecting another signal or circuit
Note 1 to entry: For PolSAR sensor, if the transmitting channel is horizontally (H) polarized, the cross-talk
on transmitting defines the ratio of V polarization transmitting power to H polarization transmitting power,
expressed in decibels (dB). The cross-talk on receiving is similar to that on transmitting.
3.11
digital elevation model
DEM
dataset of elevation values that are assigned algorithmically to 2-dimensional coordinates
[SOURCE: ISO/TS 19101-2:2008, 4.5]
3.12
height
h, H
distance of a point from a chosen reference surface measured upward along a line perpendicular to
that surface
Note 1 to entry: A height below the reference surface will have a negative value.
Note 2 to entry: The terms elevation and height are synonyms.
[SOURCE: ISO 19111:2007, 4.29 — modified: Note 2 to entry has been added.]
3.13
incident angle
vertical angle between the line from the detected element to the sensor and the local surface normal
(tangent plane normal)
[SOURCE: ISO/TS 19130:2010, 4.57]
3.14
interferometric baseline
distance between the two antenna phase centre vectors at the time when a given scatterer is imaged
3.15
integrated side lobe ratio
ISLR
ratio between the side lobe power and the main lobe power of the impulse response of point targets in
the radar imaging scene
Note 1 to entry: The integrated side lobe ratio (ISLR) can be obtained by integrating the power of the impulse
response over suitable regions. The ISLR is expressed as
 PP− 
 
total main
ISLR =10log
 
P
 
 main 
where
P is the total power;
total
P is the main lobe power.
main
Note 2 to entry: The main lobe width can be taken as α times the impulse response width (IRW), centred around
the peak, where α is a predefined constant, usually between 2 and 2,5.
3.16
interferometric synthetic aperture radar
InSAR
technique exploiting two or more SAR images to generate maps of surface deformation or digital
elevation through the differences in the phase of the waves returning to the radar
3.17
look angle
vertical angle from the platform down direction to the slant range direction, usually measured at the
aperture reference point (ARP)
Note 1 to entry: “Off-nadir angle” has the same definition as “look angle”.
[SOURCE: ISO/TS 19130-2:2014, 4.42, modified — new Note 1 to entry has replaced the original Note 1
to entry.]
3.18
metadata
information about a resource
[SOURCE: ISO 19115-1:2014, 4.10]
3.19
peak side lobe ratio
PSLR
ratio between the peak power of the largest side lobe and the peak power of the main lobe of the impulse
response of point targets in the SAR image
Note 1 to entry: The peak side lobe ratio is usually expressed in decibels (dB) and computed as follows:
 P 
 sidepeak 
PSLR =10log
 
P
 mainpeak 
 
where
P is the peak power of the main lobe;
mainpeak
P is the peak power of the largest side lobe
sidepeak
4 © ISO 2018 – All rights reserved

3.20
polarimetric synthetic aperture radar
SAR sensor enhanced by transmitting and receiving in different combinations of polarization
Note 1 to entry: By combining multiple polarization modes, it is possible to characterize the target more clearly.
Quad-Pol SAR system both transmits and receives orthogonal (e.g. horizontal and vertical) polarizations,
which creates four polarizations of a single imaging scene. The calibration of Quad-Pol SAR is addressed in this
document.
3.21
polarization channel imbalance
bias in the estimation of the scattering matrix element ratio between coincident pixels from two
coherent data channels
Note 1 to entry: Polarization channel imbalance includes the amplitude imbalance and phase imbalance.
3.22
pulse repetition frequency
number of times the system (e.g. LIDAR) emits pulses over a given time period, usually stated in
kilohertz (kHz)
[SOURCE: ISO/TS 19130-2:2014, 4.53]
3.23
radar cross section
measure of the capability of the object to scatter the transmitted radar power
Note 1 to entry: Radar cross section is calculated as
E
2 s
σ = lim 4πR
R→∞
E
i
where
σ is the radar cross section;
E is the electric-field strength of the incident wave;
i
E is the electric-field strength of the scattered wave at the radar with a distance R away from the target.
s
Note 2 to entry: Radar cross section has the dimensions of area, with the unit of square metres. Usually, it is
expressed in the form of a logarithm with the unit of dBsm as follows:
σσ=10log
dBsm 10
3.24
range
distance between the antenna and a distant object, synonymous with slant range
[SOURCE: ISO/TS 19130-2:2014, 4.54]
3.25
range bin
group of radar returns that all have the same range
[SOURCE: ISO/TS 19130:2010, 4.69]
3.26
range direction
slant range direction
direction of the range vector
[SOURCE: ISO/TS 19130:2010, 4.70]
3.27
range resolution
spatial resolution in the range direction
Note 1 to entry: For a SAR sensor, it is usually measured in terms of the impulse response of the sensor and
processing system. It is a function of the bandwidth of the pulse.
Note 2 to entry: 3 dB width of the impulse response is the normal value of measurements.
[SOURCE: ISO/TS 19130:2010, 4.71 — modified: Added Note 2 to entry.]
3.28
remote sensing
collection and interpretation of information about an object without being in physical contact with
the object
[SOURCE: ISO/TS 19101-2:2008, 4.33]
3.29
resolution (of imagery)
smallest distance between two uniformly illuminated objects that can be separately resolved in an image
Note 1 to entry: This definition refers to the spatial resolution.
Note 2 to entry: In the general case, the resolution determines the possibility to distinguish between neighbouring
features (objects).
Note 3 to entry: Resolution can also refer to the spectral and the temporal resolution.
[SOURCE: ISO/TS 19130-2:2014, 4.61 — modified: Added Notes 1, 2 and 3 to entry.]
3.30
scattering matrix
matrix characterizing the scattering process at the target of interest for polarimetric SAR
Note 1 to entry: Scattering matrix is defined by
s i
   
jkR
E E
S S 
e HH HV
H H
   
=  
    
s i
R
S S
   
E VH VV E
 
 V   V 
where
 
S S
 
HH HV
is the scattering matrix;
 
S S
 VH VV 
6 © ISO 2018 – All rights reserved

i
 
E
H
 
is the electronic field vector of the wave incident on the scatterer;
 
i
 
E
 V 
s
 
E
H
 
is the electronic field vector of the scattered wave;
 
s
 
E
 V 
k is the wavenumber of the illuminating wave;
R is the distance between the target and the radar antenna.
3.31
sensor
element of a measuring system that is directly affected by a phenomenon, body, or substance carrying
a quantity to be measured
Note 1 to entry: Active or passive sensors exist. Often two or more sensors are combined to a measuring system.
[SOURCE: ISO/IEC Guide 99:2007, 3.8 — modified: The EXAMPLE and NOTE were replaced by Note 1
to entry.]
3.32
uncertainty
parameter, associated with the result of measurement, that characterizes the dispersion of values that
could reasonably be attributed to the measurand
Note 1 to entry: The parameter may be, for example, a standard deviation (or a given multiple of it), or the half-
width of an interval having a stated level of confidence.
Note 2 to entry: Uncertainty of measurement comprises, in general, many components. Some of these
components may be evaluated from the statistical distribution of the results of series of measurements and can
be characterized by experimental standard deviations. The other components, which can also be characterized
by standard deviations, are evaluated from assumed probability distributions based on experience or other
information.
Note 3 to entry: It is understood that the result of the measurement is the best estimate of the value of the
measurand, and that all components of uncertainty, including those arising from systematic effects, such as
components associated with corrections and reference standards, contribute to the dispersion.
Note 4 to entry: When the quality of accuracy or precision of measured values, such as coordinates, is to be
characterized quantitatively, the quality parameter is an estimate of the uncertainty of the measurement results.
Because accuracy is a qualitative concept, one should not use it quantitatively, that is associate numbers with it;
numbers should be associated with measures of uncertainty instead.
Note 5 to entry: Measurement uncertainty includes components arising from systematic effects, such as
components associated with corrections and the assigned quantity values of measurement standards, as well
as the definitional uncertainty. Sometimes estimated systematic effects are not corrected for but, instead,
associated measurement uncertainty components are incorporated.
Note 6 to entry: The parameter may be, for example, a standard deviation called standard measurement
uncertainty (or a specified multiple of it), or the half-width of an interval, having a stated coverage probability.
Note 7 to entry: Measurement uncertainty comprises, in general, many components. Some of these may be
evaluated by Type A evaluation of measurement uncertainty from the statistical distribution of the quantity
values from series of measurements and can be characterized by standard deviations. The other components,
which may be evaluated by Type B evaluation of measurement uncertainty, can also be characterized by standard
deviations, evaluated from probability density functions based on experience or other information.
Note 8 to entry: In general, for a given set of information, it is understood that the measurement uncertainty
is associated with a stated quality value attributed to the measurand. A modification of this value results in a
modification of the associated uncertainty.
[SOURCE: ISO 19116:2004, 4.26 modified: Added Notes 1, 2, 3, 5, 6, 7 and 8 to entry.]
3.33
validation
process of assessing, by independent means, the quality of the data products derived from the
system outputs
Note 1 to entry: In this document, the term validation is used in a limited sense and only relates to the validation
of calibration data in order to control their change over time.
[SOURCE: ISO/TS 19101-2:2008, 4.41]
4 Symbols, abbreviated terms and conventions
In this document, conceptual schemas are presented in the Unified Modelling Language (UML).
ISO 19103 conceptual schema language presents the specific profile of UML used here.
4.1 Symbols
A area of the ground resolution cell
B length of the interferometric baseline vector
f doppler centroid frequency
d
f sampling frequency
s
f amplitude and phase imbalance between the H and V channels on receive
f amplitude and phase imbalance between the H and V channels on transmit
G imaging processor gain
p
G gain in the radar receiver
r
transmit antenna gain in the maximum-gain direction
A
G
t
receive antenna gain in the maximum-gain direction
A
G
r
A receive antenna elevation pattern which is normalized to unit gain in the maximum-gain direction
g ()θ
r
A transmit antenna elevation pattern which is normalized to unit gain in the maximum-gain
g ()θ
t
direction
H height of the antenna relative to the reference plane
h height of the target relative to the reference plane
K calibration coefficient
c
K overall radar system gain
s
L atmospheric propagation attenuation loss
a
L system loss
s
8 © ISO 2018 – All rights reserved

N matrix characterizes the additive noise term of PolSAR sensor
P image pixel power
I
P additive noise power
n
P peak transmitted power
t
PRF pulse repetition frequency
p InSAR collection mode sign, p = 1 for standard mode and p = 2 for ping-pong mode
R range from the antenna phase centre to the target
R matrix characterizes the radar receive system of PolSAR sensor
R radius of earth at the equator
e
R polar radius of earth
p
S ideal scattering matrix
T matrix characterizes the radar transmit system of PolSAR sensor
t azimuth imaging time
i
t azimuth imaging start time
Y measured scattering matrix
α angle the interferometric baseline makes with respect to a reference horizontal plane
δ cross-talk from H channel to V channel on receive
δ cross-talk from V channel to H channel on receive
δ cross-talk from H channel to V channel on transmit
δ cross-talk from V channel to H channel on transmit
θ look angle
λ radar wavelength
σ radar cross section
σ scattering coefficient
τ time delay from radar to the first range sample
φ interferometric phase

antenna phase centre position vector
S

target position vector
T

antenna phase centre velocity vector
V
4.2 Abbreviated terms
ARC Active Radar Calibrator
CRS Coordinate Reference System
DEM Digital Elevation Model
DInSAR Differential Interferometric SAR
GCP Ground Control Point
GNSS Global Navigation Satellite System
IMU Inertial Measurement Unit
InSAR Interferometric Synthetic Aperture Radar
ISLR Integrated Side Lobe Ratio
NESZ Noise Equivalent Sigma Zero
Radar RAdio Detection And Ranging
PolSAR Polarimetric Synthetic Aperture Radar
PRF Pulse Repetition Frequency
PSLR Peak Side Lobe Ratio
RCS Radar Cross Section
SAR Synthetic Aperture Radar
UML Unified Modelling Language
4.3 Conventions
ISO 19103 requires that names of UML classes, with the exception of basic data type classes, include a
two-letter prefix that identifies the standard and the UML package in which the class is defined. Table 1
lists the prefixes used in this document, the International Standard in which each is defined and the
package each identifies. UML classes defined in this document belong to a package named Calibration
Validation and have the same two letter prefixes as ISO/TS 19159-1 and ISO/TS 19159-2 CA.
Table 1 — UML class prefixes
Prefix International Standard Package
CA ISO/TS 19159-1, ISO/TS 19159-2 and ISO/TS 19159-3 (this document) Calibration Validation
MD ISO 19115-1 Metadata
SD ISO/TS 19130 Sensor Data
SE ISO/TS 19130-2 Sensor Data Extensions
SC ISO 19111 Spatial Coordinates
DQ ISO 19157 Data quality
TM ISO 19108 Temporal Schema
10 © ISO 2018 – All rights reserved

5 Conformance
This document specifies three conformance classes. Details of the conformance classes are given in the
abstract test suite in Annex A. Any set of calibration and validation information of SAR sensors, InSAR
sensors or Polarimetric SAR (PolSAR) sensors, claiming conformance to this document shall satisfy the
requirements described in the abstract test suite A.1, A.2 or A.3, respectively.
6 General SAR sensor calibration model
6.1 Introduction
This document addresses the calibration of SAR/InSAR sensors and validation of SAR/InSAR calibration
information. It includes the detailed description of SAR performance and parameters related to SAR
geometric and radiometric calibration, which can be used for refined SAR image processing.
Figure 1 depicts a package diagram that shows all parts of the ISO/TS 19159 series as of the time this
document was developed.
Figure 1 — Package diagram of the package CalibrationValidation
SAR is a kind of imaging radar. As an active system, SAR provides its own illumination and it is not
dependent on light from the sun. Furthermore, depending on the frequency microwaves can penetrate
through cloud, fog and rain. Consequently, SAR has the ability to observe the earth in both day and
night, and for almost all weather conditions.
SAR transmits successive radar pulses to illuminate the target scene and receives echo pulses from a
side-looking antenna mounted on a moving platform to create an image. Different from real aperture
radar, SAR is a coherent system in which both phase and amplitude of the echo pulses are preserved.
As a result, SAR creates a large virtual antenna known as synthetic aperture, by moving the real sensor
antenna along the flight direction and synthesizing the information of a series of received pulses within
the synthetic antenna length. This method improves the azimuth resolution considerably without
increasing the physical antenna size.
In the range direction, the pulse compression technique is used by SAR to achieve both high resolution
and high signal-to-noise ratio. SAR system usually employs a chirp pulse, which is linearly modulated
in frequency for the duration of time. The received pulse is then processed with a matched filter which
compresses the long pulse to very short pulse duration.
Interferometric SAR (InSAR) combines complex SAR images recorded by antennas at different
locations or at different times. The range differences for corresponding points of the image pair can
be determined by the interferograms on the sub-wavelength scale. It can be used as an alternative to
conventional stereo photographic techniques for topographic map generation. InSAR can also be used
for velocity mapping and surface deformation detection.
Radar polarimetry is concerned with the full vector nature of polarized radar waves. It can be used
for extraction of target properties from the behaviour of scattered waves from a target. Polarimetric
SAR (PolSAR), the incorporation of coherent polarimetric phase and amplitude into SAR signal, brings
about further improvements in monitoring capabilities such as land-use classification, forest mapping,
biomass estimation, target identification, emergency response and damage assessment.
Polarimetric SAR interferometry (PolInSAR) is a technique which combines the advantages of InSAR
and PolSAR. It provides combined sensitivity to the vertical distribution of scattering mechanisms and
has the capacity to optimize the quality of height estimation. It is very useful in the field of physical
parameter inversion and hidden surface/target imaging.
Calibration is the process of quantitatively defining a system’s response to controlled signal inputs. SAR
calibration contains two aspects, geometry and radiometry.
For many applications, such as geologic mapping and land surveys, the geometric fidelity of the data
product is very important. For the sake of high geometric accuracy, geometric calibration is essential to
measure various error sources.
The purpose of SAR radiometric calibration is characterizing the performance of the end-to-end SAR
system so that the real radiometric parameters of ground targets, i.e. RCS or backscattering coefficients,
can be derived from the SAR image.
However, calibration is often a costly and time consuming process. Therefore, simplified intermediate
calibration procedures are carried out to bridge the time gap between subsequent calibrations and
ensure a long-term confidence in the quality.
For specific SAR acquisition modes, such as InSAR and PolSAR, additional parameters should be
calibrated to improve the product quality besides ordinary geometric and radiometric calibration.
This clause describes the general model of SAR sensor calibration and validation of calibration
information. InSAR and PolSAR sensors are described in Clauses 7 and 8, respectively. Calibration and
validation of PolInSAR is not addressed in this document.
6.2 Top-level model
Figure 2 depicts the top-level class diagram of this document. The classes shown in Figure 2, their
attributes and their associations shall be used as described in the data dictionary of B.2, B.12.1 and in
ISO/TS 19130-2.
12 © ISO 2018 – All rights reserved

Figure 2 — Top-level class diagram of ISO/TS 19159-3
The class CA_SARSensor is a top level class for all information of calibration and validation of SAR sensors.
It aggregates seven classes named CA_Radar-System, CA_AntennaSystem, CA_AntennaPhaseCentre,
CA_SignalProcessing, CA_Atmospheric-PropagationAndEarthMotion, CA_SARCalibrationField and
CA_SARValidation. Details of the radar system are shown in Figure 3, of the antenna system are shown
in Figure 4, of the antenna phase centre are shown in Figure 5, of the signal processing are shown in
Figure 6, of the atmospheric propagation and earth motion are shown in Figure 7, of the calibration
field are shown in Figure 8, of SAR validation are shown in Figure 9.
It has two subclasses named CA_InSARSensor and CA_PolSARSensor which are shown in Figure 11 and
Figure 12, respectively.
The attribute collectionMode defines the method used by SAR system to collect data.
The attribute acquisitionMode defines the acquisition mode of SAR system according to the code list set
in the class CA_SARAcquisitionMode.
The attribute centreFrequency defines the centre frequency of the SAR sensor.
The attribute bandwidth defines the bandwidth of transmitted signal.
The attribute antennaNumber defines the number of antennas of SAR system.
The attribute transmitAndReceiveChannelNumber defines the channel number of SAR system. One
channel refers to one transmitting and receiving channel. General SAR has one channel. Dual antenna
InSAR has two channels even if it operates in the standard mode that one antenna transmits and both
antennas receive echoes. Full polarimetric SAR has four channels whose polarimetric modes are HH,
HV, VH and VV respectively.
6.3 Radar system
The radar generates pulses by the transmitter and radiates them into space by the antenna. A fraction
of the radar signal is returned from the reflecting targets in the direction of the radar. The returned
echo is collected by the antenna and amplified by the receiver. SAR is a kind of imaging radar. This
clause describes radar system parameters related to SAR calibration except antenna parameters, which
is described in Clause 6.4.
Figure 3 depicts the class diagram of radar system. The classes shown in Figure 3, their attributes and
their associations shall be used as described in the data dictionary of B.3.
Figure 3 — CA_RadarSystem
The class CA_RadarSystem contains all information about the radar system of SAR sensor.
The attribute transmitPower defines peak transmitted power of radar system.
The attribute samplingDelay defines the echo reception time delay of the first range sample with
respect to the pulse transmitted time.
The attribute samplingFrequency defines the range sampling frequency.
The attribute pulseStartTime defines the azimuth time of the first pulse.
The attribute prf defines the radar pulse repetition frequency. This document only addresses calibration
of general SAR/InSAR system working on a fixed PRF. Systems with complex working modes, calibration
will be closely related with basic SAR system data acquisition. It may be discussed in a future part of
ISO TS 19159.
14 © ISO 2018 – All rights reserved

The attribute dynamicRange defines the range of input signal strength over which the receiver can
amplify the input signal linearly.
The attribute nesz defines noise equivalent sigma zero of the radar system. It is a measure of the
sensitivity of the system to areas of low radar backscatter and is given by the value of the backscattering
coefficient corresponding to a signal-to-noise ratio of unity.
The attribute echopulseNumber defines the number of received pulses.
The attribute sampleNumber defines the number of samples of one pulse.
The attribute receiverGain defines the gain of radar receiver.
The attribute replicaSignal defines a replica of the transmitted pulse injected into the data stream
during the quiet periods between pulse transmission and echo reception, which is used to determine
the exact range compression function in the signal processor.
The calibrationCoefficient defines the ratio of SAR image pixel power to RCS without considering
additive noise, after the processor gain is normalized to one, elevation antenna pattern, range and
atmospheric attenuation are all corrected.
The class CA_Complex is a datatype that defines a complex number.
The attribute amplitude defines the amplitude of a complex number.
The attribute phase defines the phase of a complex number.
6.4 Antenna system
The basic role of the antenna is to provide a tranducer to transmit or receive electromagnetic waves. A
single antenna can be used for both transmitting and receiving. This holds true for most SAR systems.
However, there are exceptions such as bistatic SAR which must have separated transmit and receive
antennas. The key parameters affecting the SAR performance include the antenna gain and its beam
pattern. This clause describes useful information of SAR antenna system used for SAR radiometric
calibration. This document only addresses calibration of general SAR/InSAR systems with a simple
antenna system. Systems with advanced antennas may be discussed in a future part of ISO TS 19159.
Figure 4 depicts the class diagram of antenna system. The classes shown in Figure 4, their attributes and
their associations shall be used as described in the data dictionary of B.4, B.12.2 and in ISO/TS 19130.
Figure 4 — CA_AntennaSystem
The class CA_AntennaSystem contains all information about the antenna of SAR sensor.
The attribute orientationMode defines the antenna orientation.
The attribute polarimetryList defines the antenna polarimetric mode.
The attribute gain defines the antenna power gain.
The attribute azimuthPointingAngle defines the pointing angle of azimuth antenna beam.
The attribute elevationPointingAngle defines the pointing angle of elevation antenna beam.
The attribute elevationPattern defines the elevation antenna pattern.
The attribute azimuthPattern defines the azimuth antenna pattern.
The class CA_Pattern is a datatype that defines one dimensional antenna pattern.
The attribute patternAngle defines
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