ISO/TS 19130:2010

TECHNICAL ISO/TS
SPECIFICATION 19130
First edition
2010-06-15
Geographic information — Imagery
sensor models for geopositioning
Information géographique — Modèles de capteurs d'images de
géopositionnement
Reference number
©
ISO 2010
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ii © ISO 2010 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Conformance .1
3 Normative references.2
4 Terms and definitions .2
5 Symbols and abbreviated terms .11
5.1 Abbreviated terms .11
5.2 Notation .13
6 Image geopositioning: overview and common elements .13
6.1 Introduction.13
6.2 Type of geopositioning information .14
6.3 Calibration data .15
6.4 Ground control points.16
7 Physical Sensor Models .19
7.1 Sensor types .19
7.2 Physical Sensor Model approach .23
7.3 Quality associated with Physical Sensor Models .29
7.4 Physical Sensor Model metadata .31
7.5 Location and orientation.32
7.6 Sensor parameters .37
8 True Replacement Models and Correspondence Models .43
8.1 Functional fitting .43
8.2 True Replacement Model approach.44
8.3 Quality associated with a True Replacement Model.50
8.4 Schema for True Replacement Model .52
8.5 Correspondence Model approach .53
8.6 Schema for Correspondence Models.56
Annex A (normative) Conformance and testing .57
Annex B (normative) Geolocation information data dictionary .60
Annex C (normative) Coordinate systems .77
Annex D (informative) Frame sensor model metadata profile supporting precise geopositioning .106
Annex E (informative) Pushbroom / Whiskbroom sensor model metadata profile.114
Annex F (informative) Synthetic Aperture Radar sensor model metadata profile supporting
precise geopositioning .128
Bibliography.140

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 organizations, governmental and
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International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of normative document:
⎯ an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
⎯ an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a
further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an
International Standard or be withdrawn.
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.
ISO/TS 19130 was prepared by Technical Committee ISO/TC 211, Geographic information/Geomatics.
iv © ISO 2010 – All rights reserved

Introduction
The purpose of this Technical Specification is to specify the geolocation information that an imagery data
provider shall supply in order for the user to be able to find the earth location of the data using a Physical
Sensor Model, a True Replacement Model or a Correspondence Model. Detailed Physical Sensor Models are
defined for passive electro-optical visible/infrared (IR) sensors (frame, pushbroom and whiskbroom) and for an
active microwave sensing system (Synthetic Aperture Radar). A set of components from which models for
other sensors can be constructed is also provided. Metadata required for geopositioning using a True
Replacement Model, a Correspondence Model, or ground control points are also specified. The intent is to
standardize sensor descriptions and specify the minimum geolocation metadata requirements for data
providers and geopositioning imagery systems.
Vast amounts of data from imaging systems are collected, processed and distributed by government mapping
and remote sensing agencies and commercial data vendors. In order for this data to be useful in extraction of
geographic information, it requires further processing. Geopositioning, which determines the ground
coordinates of an object from image coordinates, is a fundamental processing step. Because of the diversity
of sensor types and the lack of a common sensor model standard, data from different producers can contain
different parametric information, lack parameters required to describe the sensor that produces the data, or
lack ancillary information necessary for geopositioning and analysing the data. Consequently, a separate
software package often has to be developed to deal with data from each individual sensor or data producer.
Standard sensor models and geolocation metadata allow agencies or vendors to develop generalized
software products that are applicable to data from multiple data producers or from multiple sensors. With such
a standard, different producers can describe the geolocation information of their data in the same way, thus
promoting interoperability of data between application systems and facilitating data exchange.
This Technical Specification defines the set of metadata elements specified for providing sensor model and
other geopositioning data to users. For the case where a Physical Sensor Model is provided, it includes a
location model and metadata relevant to all sensors; it also includes metadata specific to whiskbroom,
pushbroom, frame, and SAR sensors. It also includes metadata for functional fit geopositioning, where the
function is part of a Correspondence Model or a True Replacement Model. This Technical Specification also
provides a schema for all of these metadata elements.
TECHNICAL SPECIFICATION ISO/TS 19130:2010(E)

Geographic information — Imagery sensor models for
geopositioning
1 Scope
This Technical Specification identifies the information required to determine the relationship between the
position of a remotely sensed pixel in image coordinates and its geoposition. It supports exploitation of
remotely sensed images. It defines the metadata to be distributed with the image to enable user determination
of geographic position from the observations.
This Technical Specification specifies several ways in which information in support of geopositioning may be
provided.
a) It may be provided as a sensor description with the associated physical and geometric information
necessary to rigorously construct a Physical Sensor Model. For the case where precise geoposition
information is needed, this Technical Specification identifies the mathematical formulae for rigorously
constructing Physical Sensor Models that relate two-dimensional image space to three-dimensional
ground space and the calculation of the associated propagated errors. This Technical Specification
provides detailed information for three types of passive electro-optical/infrared (IR) sensors (frame,
pushbroom and whiskbroom) and for an active microwave sensing system [Synthetic Aperture Radar
(SAR)]. It provides a framework by which these sensor models can be extended to other sensor types.
b) It may be provided as a True Replacement Model, using functions whose coefficients are based on a
Physical Sensor Model so that they provide information for precise geopositioning, including the
calculation of errors, as precisely as the Physical Sensor Model they replace.
c) It may be provided as a Correspondence Model that provides a functional fitting based on observed
relationships between the geopositions of a set of ground control points and their image coordinates.
d) It may be provided as a set of ground control points that can be used to develop a Correspondence
Model or to refine a Physical Sensor Model or True Replacement Model.
This Technical Specification does not specify either how users derive geoposition data or the format or
content of the data the users generate.
2 Conformance
This Technical Specification specifies four conformance classes. There is one conformance class for each of
the methods specified for providing geopositioning information. Any set of geopositioning information claiming
conformance to this Technical Specification shall satisfy the requirements for at least one conformance class
as specified in Table 1. The requirements for each class are shown by the presence of an X in the boxes for
all clauses in the application test suite (ATS) required for that class. If the requirement is conditional, the box
contains a C.
Table 1 — Conformance classes
Subclause
A.1 A.2.1 A.2.2 A.3.1 A.3.2 A.3.3 A.3.4 A.3.5 A.4 A.5 A.6
Correspondence Model X X X   X X
Physical SAR X  X X X X
Sensor
electro- X  X X X X
Model
optical
True Replacement Model X    X X
GCP Collection X X X C C C C C C C C

3 Normative references
The following referenced documents are indispensable for the application 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/TS 19103:2005, Geographic information — Conceptual schema language
ISO 19107, Geographic information — Spatial schema
ISO 19108, Geographic information — Temporal schema
ISO 19111:2007, Geographic information — Spatial referencing by coordinates
ISO 19115:2003, Geographic information — Metadata
ISO 19115-2:2009, Geographic information — Metadata — Part 2: Extensions for imagery and gridded data
ISO 19123, Geographic information — Schema for coverage geometry and functions
ISO/TS 19138:2006 Geographic information — Data quality measures
4 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
4.1
active sensing system
sensing system that emits energy that the sensor uses to perform sensing
4.2
adjustable model parameters
model parameters that can be refined using available additional information, such as ground control points,
to improve or enhance modelling corrections
4.3
along-track
direction in which the sensor platform moves
2 © ISO 2010 – All rights reserved

Conformance Class
4.4
ARP
aperture reference point
3D location of the centre of the synthetic aperture
NOTE It is usually expressed in ECEF coordinates in metres.
4.5
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
[ISO 19116:2004, definition 4.2]
4.6
attribute
named property of an entity
[ISO/IEC 2382-17:1999, definition 17.02.12]
NOTE In this Technical Specification, the property relates to a geometrical, topological, thematic, or other
characteristic of an entity.
4.7
azimuth resolution
〈SAR〉 resolution in the cross-range direction
NOTE 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 (i.e. a larger aperture results in a longer dwell
time results in better resolution).
4.8
beam width
〈SAR〉 useful angular width of the beam of electromagnetic energy
NOTE Beam width is usually measured in radians and as the angular width between two points that have 50 % of the
power (3 dB below) of the centre of the beam. It is a property of the antenna. Power emitted outside of this angle is too
little to provide a usable return.
4.9
broadside
〈SAR〉 direction orthogonal to the velocity vector and parallel to the plane tangent to the Earth's ellipsoid at
the nadir point of the ARP
4.10
calibrated focal length
distance between the perspective centre and the image plane that is the result of balancing positive and
negative radial lens distortions during sensor calibration
4.11
coordinate
one of a sequence of n numbers designating the position of a point in n-dimensional space
[ISO 19111:2007, definition 4.5]
NOTE In a coordinate reference system, the coordinate numbers are qualified by units.
4.12
coordinate reference system
coordinate system that is related to an object by a datum
[ISO 19111:2007, definition 4.8]
NOTE For geodetic and vertical datums, the object will be the Earth.
4.13
coordinate system
set of mathematical rules for specifying how coordinates are to be assigned to points
[ISO 19111:2007, definition 4.10]
4.14
Correspondence Model
functional relationship between ground and image coordinates based on the correlation between a set of
ground control points and their corresponding image coordinates
4.15
cross-track
perpendicular to the direction in which the collection platform moves
4.16
data
reinterpretable representation of information in a formalised manner suitable for communication, interpretation,
or processing
[ISO/IEC 2382-1:1993, definition 01.01.02]
4.17
datum
parameter or set of parameters that define the position of the origin, the scale, and the orientation of a
coordinate system
[ISO 19111:2007, definition 4.14]
4.18
detector
device that generates an output signal in response to an energy input
4.19
Doppler angle
〈SAR〉 angle between the velocity vector and the range vector
4.20
Doppler shift
wavelength change resulting from relative motion of source and detector
NOTE In the SAR context, it is the frequency shift imposed on a radar signal due to relative motion between the
transmitter and the object being illuminated.
4.21
ellipsoid
surface formed by the rotation of an ellipse about a main axis
[ISO 19111:2007, definition 4.17]
NOTE The Earth ellipsoid is a mathematical ellipsoid figure of the Earth which is used as a reference frame for
computations in geodesy, astronomy and the geosciences.
4 © ISO 2010 – All rights reserved

4.22
ellipsoidal coordinate system
geodetic coordinate system
coordinate system in which position is specified by geodetic latitude, geodetic longitude and (in the three-
dimensional case) ellipsoidal height
[ISO 19111:2007, definition 4.18]
4.23
ellipsoidal height
geodetic height
h
distance of a point from the ellipsoid measured along the perpendicular from the ellipsoid to this point,
positive if upwards or outside of the ellipsoid
[ISO 19111:2007, definition 4.19]
NOTE Only used as part of a three-dimensional ellipsoidal coordinate system and never on its own.
4.24
error propagation
process of determining the uncertainties of derived quantities from the known uncertainties of the quantities on
which the derived quantity is dependent
NOTE Error propagation is governed by the mathematical function relating the derived quantity to the quantities from
which it was derived.
4.25
external coordinate reference system
coordinate reference system whose datum is independent of the object that is located by it
4.26
fiducial centre
point determined on the basis of the camera fiducial marks
NOTE When there are four fiducial marks, fiducial centre is the intersection of the two lines connecting the pairs of
opposite fiducial marks.
4.27
fiducial mark
index marks, typically four or eight rigidly connected with the camera body, which form images on the film
negative and define the image coordinate reference system
NOTE When a camera is calibrated the distances between fiducial marks are precisely measured and assigned
coordinates that assist in correcting for film distortion.
4.28
frame sensor
sensor that detects and collects all of the data for an image (frame / rectangle) at an instant of time
4.29
geodetic datum
datum describing the relationship of a two- or three-dimensional coordinate system to the Earth
[ISO 19111:2007, definition 4.24]
NOTE In most cases, the geodetic datum includes an ellipsoid description.
4.30
geodetic latitude
ellipsoidal latitude
ϕ
angle from the equatorial plane to the perpendicular to the ellipsoid through a given point, northwards treated
as positive
[ISO 19111:2007, definition 4.25]
4.31
geodetic longitude
ellipsoidal longitude
λ
angle from the prime meridian plane to the meridian plane of a given point, eastward treated as positive
[ISO 19111:2007, definition 4.26]
4.32
geoid
equipotential surface of the Earth’s gravity field which is everywhere perpendicular to the direction of gravity
and which best fits mean sea level either locally or globally
[ISO 19111:2007, definition 4.27]
4.33
geographic information
information concerning phenomena implicitly or explicitly associated with a location relative to the Earth
[ISO 19101:2002, definition 4.16]
4.34
geolocating
geopositioning an object using a Physical Sensor Model or a True Replacement Model
4.35
geolocation information
information used to determine geographic location corresponding to image location
[ISO 19115-2:2009, definition 4.11]
4.36
geopositioning
determining the geographic position of an object
NOTE While there are many methods for geopositioning, this Technical Specification is focused on geopositioning
from image coordinates.
4.37
georeferencing
geopositioning an object using a Correspondence Model derived from a set of points for which both ground
and image coordinates are known
4.38
gimbal
mechanical device consisting of two or more rings connected in such a way that each rotates freely around an
axis that is a diameter of the next ring toward the outermost ring of the set
NOTE An object mounted on a three-ring gimbal will remain horizontally suspended on a plane between the rings
regardless as to the stability of the base.
6 © ISO 2010 – All rights reserved

4.39
grazing angle
〈SAR〉 vertical angle from the local surface tangent plane to the slant range direction
4.40
grid
network composed of two or more sets of curves in which the members of each set intersect the members of
the other sets in an algorithmic way
[ISO 19123:2005, definition 4.1.23]
NOTE The curves partition a space into grid cells.
4.41
grid coordinates
sequence of two or more numbers specifying a position with respect to its location on a grid
[ISO 19115-2:2009, definition 4.16]
4.42
ground control point
point on the earth that has an accurately known geographic position
[ISO 19115-2:2009, definition 4.18]
4.43
ground range
〈SAR〉 magnitude of the range vector projected onto the ground
NOTE Ground range of an image is represented by the distance from the nadir point of the antenna to a point in the
scene. Usually measured in the horizontal plane, but can also be measured as true distance along the ground, DEM,
geoid or ellipsoid surface.
4.44
GRP
ground reference point
3D position of a reference point on the ground for a given synthetic aperture
NOTE It is usually the centre point of an image (Spotlight) or an image line (Stripmap). It is usually expressed in
ECEF coordinates in metres.
4.45
ground sampling distance
linear distance between pixel centres on the ground
NOTE This definition also applies for water surfaces.
4.46
gyroscope
device consisting of a spinning rotor mounted in a gimbal so that its axis of rotation maintains a fixed
orientation
NOTE The rotor spins on a fixed axis while the structure around it rotates or tilts. In airplanes, the pitch and
orientation of the airplane is measured against the steady spin of the gyroscope. In space, where the four compass points
are meaningless, the gyroscope’s axis of rotation is used as a reference point for navigation. An inertial navigation system
includes three gimbal-mounted gyroscopes, used to measure roll, pitch, and yaw.
4.47
image
gridded coverage whose attribute values are a numerical representation of a physical parameter
[ISO 19115-2:2009, definition 4.19]
NOTE The physical parameters are the result of measurement by a sensor or a prediction from a model.
4.48
image coordinate reference system
coordinate reference system based on an image datum
[ISO 19111:2007, definition 4.30]
4.49
image datum
engineering datum which defines the relationship of a coordinate system to an image
[ISO 19111:2007, definition 4.31]
4.50
image distortion
deviation between the actual location of an image point and the location that theoretically would result from
the geometry of the imaging process without any errors
4.51
image formation
〈SAR〉 process by which an image is generated from collected Phase History Data in a SAR system
4.52
image-identifiable ground control point
ground control point associated with a marker or other object on the ground that can be recognized in an
image
NOTE The ground control point may be marked in the image, or the user may be provided with an unambiguous
description of the ground control point so that it can be found in the image.
4.53
image plane
plane behind an imaging lens where images of objects within the depth of field of the lens are in focus
4.54
image point
point on the image that uniquely represents an object point
4.55
imagery
representation of phenomena as images produced by electronic and/or optical techniques
[ISO/TS 19101-2:2008, definition 4.14]
NOTE In this Technical Specification, it is assumed that the phenomena have been sensed or detected by one or
more devices such as radars, cameras, photometers and infrared and multispectral scanners.
4.56
impulse response
width of the return generated by a small point reflector, which equates to the smallest distance between two
point reflectors that can be distinguished as two objects
4.57
incident angle
vertical angle between the line from the detected element to the sensor and the local surface normal (tangent
plane normal)
4.58
internal coordinate reference system
coordinate reference system having a datum specified with reference to the object itself
8 © ISO 2010 – All rights reserved

4.59
metadata
data about data
[ISO 19115:2003, definition 4.5]
4.60
object point
point in the object space that is imaged by a sensor
NOTE In remote sensing and aerial photogrammetry an object point is a point defined in an Earth-fixed coordinate
reference system.
4.61
passive sensor
sensor that detects and collects energy from an independent source
EXAMPLE Many optical sensors collect reflected solar energy.
4.62
perspective centre
projection centre
point located in three dimensions through which all rays between object points and image points appear to
pass geometrically
4.63
Physical Sensor Model
sensor model based on the physical configuration of a sensing system
4.64
pixel
smallest element of a digital image to which attributes are assigned
[ISO/TS 19101-2:2008, definition 4.28]
NOTE 1 This term originated as a contraction of “picture element”.
NOTE 2 Related to the concept of a grid cell.
4.65
platform coordinate reference system
engineering coordinate reference system fixed to the collection platform within which positions on the
collection platform are defined
4.66
principal point of autocollimation
point of intersection between the image plane and the normal from the perspective centre
4.67
principal point of best symmetry
centre of the circles of equal distortion of the lens positioned in the image plane
4.68
pushbroom sensor
sensor that collects a single cross-track image line at one time and constructs a larger image from a set of
adjacent lines resulting from the along-track motion of the sensor
4.69
range bin
〈SAR〉 group of radar returns that all have the same range
4.70
range direction
slant range direction
〈SAR〉 direction of the range vector
4.71
range resolution
spatial resolution in the range direction
NOTE 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.
4.72
range vector
vector from the antenna to a point in the scene
4.73
rectified grid
grid for which there is an affine transformation between the grid coordinates and the coordinates of an
external coordinate reference system
[ISO 19123:2005, definition 4.1.32]
NOTE If the coordinate reference system is related to the Earth by a datum, the grid is a georectified grid.
4.74
remote sensing
collection and interpretation of information about an object without being in physical contact with the object
[ISO/TS 19101-2:2008, definition 4.33]
4.75
resolution (of a sensor)
smallest difference between indications of a sensor that can be meaningfully distinguished
[ISO/TS 19101-2:2008, definition 4.34]
NOTE For imagery, resolution refers to radiometric, spectral, spatial and temporal resolutions.
4.76
SAR
Synthetic Aperture Radar
imaging radar system that simulates the use of a long physical antenna by collecting multiple returns from
each target as the actual antenna moves along the track
NOTE The electromagnetic radiation is at microwave frequencies and is sent in pulses.
4.77
scan mode
SAR mode in which the antenna beam is steered to illuminate a swath of ground at various angles relative to
flight path throughout the collection
NOTE Steering the antenna also allows dwell time to be increased and provides the ability to collect strips at angles
non-parallel to the flight direction and with better resolution than Stripmap mode.
4.78
ScanSAR mode
special case of stripmap mode that uses an electronically steerable antenna to quickly change the swath
being imaged during collection to collect multiple parallel swaths in one pass
10 © ISO 2010 – All rights reserved

4.79
sensor
element of a measuring system that is directly affected by a phenomenon, body, or substance carrying a
quantity to be measured
[ISO/IEC Guide 99:2007, definition 3.8]
4.80
sensor model
〈geopositioning〉 mathematical description of the relationship between the three-dimensional object space and
the two-dimensional plane of the associated image produced by a sensor
4.81
slant plane
〈SAR〉 plane that passes through the sensor velocity vector and the GRP
4.82
slant range
〈SAR〉 magnitude of the range vector
4.83
spotlight mode
〈SAR〉 SAR mode in which the antenna beam is steered to illuminate one area during collection
NOTE Spotlight mode provides the ability to collect higher resolution SAR data over relatively smaller patches of
ground surface.
4.84
squint angle
〈SAR〉 angle measured from the broadside direction vector to the range direction vector in the slant plane
4.85
stripmap mode
〈SAR〉 SAR mode in which the antenna beam is fixed throughout the collection of an image
NOTE Doppler angle in processed products is fixed for all pixels. It provides the ability to collect SAR data over
strips of land over a fixed swath of ground range parallel to the direction of flight.
4.86
True Replacement Model
model using functions whose coefficients are based on a Physical Sensor Model
4.87
whiskbroom sensor
sensor that sweeps a detector forming cross-track image line(s) and constructs a larger image from a set of
adjacent lines using the along-track motion of the sensor’s collection platform
5 Symbols and abbreviated terms
5.1 Abbreviated terms
ARP Aperture Reference Point
CCD Charge-Coupled Device
CCS Common Coordinate System
CM Correspondence Model
CRS Coordinate Reference System
DEM Digital Elevation Model
DLT Direct Linear Transform
ECEF Earth-Centred, Earth-Fixed
ENU East-North-Up
EO Exterior Orientation
FSP Flight Stabilization Platform
GCP Ground Control Point
GNSS Global Navigation Satellite System
GRP Ground Reference Point
GSD Ground Sample Distance
IMU Inertial Measurement Unit
INS Inertial Navigation System
IRF Inertial Reference Frame
IPR Impulse Response
IR Infrared
MSL Mean Sea Level
NED North-East-Down
PHD Phase History Data
PSM Physical Sensor Model
RAR Real Aperture Radar
RMS Root Mean Square
RPC Rational Polynomial Coefficient
RSM Replacement Sensor Model
SAR Synthetic Aperture Radar
SCS Sensor Coordinate System
TRM True Replacement Model
WGS 84 World Geodetic System 1984
2D Two-dimensional
3D Three-dimensional
12 © ISO 2010 – All rights reserved

5.2 Notation
Clauses 6, 7, and 8 of this Technical Specification present a conceptual schema, specified in the Unified
Modeling Language (UML), describing the characteristics of sensor models. ISO/TS 19103 describes the way
in which UML is used in the ISO 19100 family of standards. It differs from standard UML only in the existence
and interpretation of some special stereotypes, in particular, “CodeList” and “Union”. ISO/TS 19103 specifies
the basic data types used in the UML model and the data dictionary in this Technical Specification.
Annex B contains a data dictionary for the UML diagrams in this schema.
ISO/TS 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 2 lists
the prefixes used in this Technical Specification, the International Standard in which each is defined and the
package each identifies. UML classes defined in this Technical Specification belong to a package named
Sensor Data and have the two letter prefix SD.
Table 2 — UML class prefixes
Prefix Standard Package
CI ISO 19115 Citation
CV ISO 19123 Coverages
DQ ISO 19115 Data quality
GM ISO 19107 Geometry
MD ISO 19115 Metadata
MI ISO 19115-2 Metadata for Imagery
SC ISO 19111 Spatial Coordinates
SD ISO 19130 Sensor Data
TM ISO 19108 Temporal Schema
6 Image geopositioning: overview and common elements
6.1 Introduction
An “image” is a two-dimensional set of contiguous pixels. Associated with each pixel in the image is either a
single response value, as in a panchromatic image; three response values in red, green, and blue, as in a
colour image; or many values, as in multi-and hyper-spectral images. Geopositioning information applies to
the pixel, regardless of how many response values are associated with that pixel.
Image geopositioning is the process of determining the Earth coordinates of an object from image coordinates.
Geolocation information is the information necessary for the geopositioning methods to work. Features in
Earth imagery can be geopositioned by different approaches. The data provider shall identify to the user which
method was used.
In order to determine the three-dimensional Earth coordinates of features and the quality associated with
those coordinates (rigorously expressed by covariance matrices) accurately, two approaches exist, both
ultimately based on the physical configuration of the sensor:
a) Physical Sensor Models (PSMs)
b) True Replacement Models (TRMs)
A third approach is based on:
c) Correspondence Models (CMs)
The most rigorous approach for geopositioning of imagery is to use the mathematical representation of the
physics and geometry of the image sensing system, which is referred to as the Physical Sensor Model. That
model is used extensively in photogrammetric applications for precise geopositioning. In order to precisely
determine geoposition from imagery, certain steps need to be performed. The first and most fundamental step
is to construct, mathematically, the sensor model that corresponds to the type of sensor under consideration.
Then, information relating the sensing event to the ground reference coordinate system is needed to apply the
model to a given image. This information can be in one of two forms:
a) accurate data about the position, attitude, and dynamics of the sensor during imaging; or
b) ground control information such as a set of Global Navigation Satellite System (GNSS)-determined
ground control points (GCPs).
TRMs are produced using Physical Sensor Models. The equations that describe the sensor and its
relationship to the Earth coordinate reference system are replaced with a set of equations that directly
describe the relationship between image coordinates and Earth coordinates.
Geopositioning that applies correspondence modelling, called georeferencing, uses image information and
ground control points only. CMs are quite varied and may deal with only horizontal (e.g., longitude and
latitude) coordinates, or with all three coordinates (e.g., longitude, latitude and elevation). They all have in
common the fact that they do not make use of the Physical Sensor Model and consequently cannot apply
rigorous error propagation. Thus, Correspondence Models are generally less accurate than methods based on
Physical Sensor Models. Neither a geometric model of the sensor that took the image nor information about
its position and orientation is required. This georeferencing method has been widely applied to remotely
sensed imagery. For instance, the geographic location of an image can be established using a two-
dimensional polynomial function based on a number of common points that relate the image to the surface of
the Earth. The simplest way to georeference an image is by defining the Earth coordinates of the image
corners.
This Technical Specification defines the geopositioning information for supporting the above-stated
approaches for geopositioning images. Clause 7 covers the Physical Sensor Model approach and Clause 8
covers True Replacement Models and Correspondence Models.
6.2 Type of geopositioning information
Geopositioning information shall be provided in one of the ways shown in Figure 1:
a) A set of ground control points (MI_GCPCollection) and optional quality information as specified in
ISO 19115-2 and further specified in 6.4 of this Technical Specification. The recipient can use this
information to generate his own fitting function for use in a Correspondence Model.
b) A sensor model (SD_SensorModel) as specified in this Technical Specification. An instance of
SD_SensorModel provides geopositioning information for the single image identified by the attribute
forImageID. SD_SensorModel is an aggregate of one or more instances of one, but no more than one, of
the three sensor model types specified in this Technical Specification. This allows for spatial
segmentation of the image such that there is one instance of the model type for each segment. The three
specified sensor model types are:
1) Physical Sensor Model (SD_PhysicalSensorModel),
2) True Replacement Model ( SD_TrueReplacementModel), and
3) Correspondence Model (SD_CorrespondenceModel).
14 © ISO 2010 – All rights reserved

The classes shown in Figure 1, their attributes and their associations shall be used as specified in the data
dictionary of B.2.1.
class SD_SensorModel (1)
«Abstract»
Metadata for Imagery::
MI_GeolocationInformation
SD_SensorModel
+ forImageID: CharacterString
{XOR}
1.* +physicalSensorModel
SD_PhysicalSensorModel
1.* +trueReplacementModel
SD_TrueReplacementModel
1.*
SD_CorrespondenceModel
+correspondenceModel
Metadata for Imagery::MI_GCPCollection

Figure 1 — SD_SensorModel
6.3 Calibration data
6.3.1 Introduction
Sensor calibration is a significant input to sensor modelling. There are two types of calibration data: geometric
and radiometric. Geometric calibration data is critical for precise geopositioning from imagery. Radiometric
calibration is needed for quantitative estimation of geophysical parameters and interpretation of the physical
and geographical significance of the measurements.
6.3.2 Geometric calibration
Sensor geometric calibration data are either available in the metadata from laboratory calibration or can
actually be determined during photogrammetric processing of the imagery. Calibration parameters are defined
according to the type of sensor. For electro-optical sensors, common parameters include calibrated focal
length, principal point offset, radial lens distortion coefficients, tangential or decentring lens distortion
coefficients and sensor array distortions such as differential scale and skew.
6.3.3 Radiometric calibration
Radiometric calibration refers to operations intended to remove systematic or random noise that affect the
amplitude of the image function. Radiometric calibration includes correcting the data for sensor irregularities
and unwanted sensor or atmospheric noise, and converting the data so they accurately represent the reflected
or emitted radiation measured by the sensor.
This specification is concerned with those aspects of radiometric calibration that involve adjustment of the
non-uniform response of the different elements of the sensor array to improve the relative spectral and
temporal fidelity of the current data acquisition. In particular, the process which normalizes these responses
and the values from in-flight and la
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