09-108b Grid CRS URNs
Open Geospatial Consortium
Document OGC 09-108
CR-Form-v3
CHANGE REQUEST
OGC URNs for CR ?
definitions
rev
Current version:
-
For HELP on using this form, see bottom of this page or look at the pop-up text over the symbols.
Proposed change affects:
AS
Imp Spec
Best Practices Paper
Title:
OGN URN change request: Add grid CRS URNs
Source:
Arliss Whiteside and other WCS SWG members
Work item code:
Category:
Other X
Date: 2009-09-09
B (Addition of feature)
Use one of the following categories:
F (Critical correction)
A (corresponds to a correction in an earlier release)
B (Addition of feature),
C (Functional modification of feature)
D (Editorial modification)
Reason for change:
URNs in the “ogc” URN namespace are often effective and efficient for
referencing the definitions of CRSs and their components. A set of these
URNs for ImageCRSs was thus specified in Clause 10 of approved
Implementation Specification OGC 05-096r1 “GML 3.1.1 grid CRSs profile”.
However, those URNs have not yet been accepted by the more-recentlyformed OGC Naming Authority.
Summary of change: Add definitions of eight URNs for definitions of ImageCRSs and their
components, to the registry of URNs approved by the OGC Naming Authority
Consequences if
not approved:
Failure to allow previously specified URNs for ImageCRSs and their
components, some of which are being used with WCS 1.1.
Clauses affected:
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.
1
OGC 09-108
Other specs
X Other core specifications
Affected:
WCS 1.1, GML 3.1.1 grid CRSs profile
Abstract specifications
Best Practices Papers
Supporting Doc.
Other comments:
Status
Disposition
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
2
OGC 09-108
Contents
Page
1
Introduction..............................................................................................................2
2
2D Grid coordinate system......................................................................................3
3
Row coordinate axis.................................................................................................4
4
Column coordinate axis...........................................................................................5
5
Grid spacing unit of measure...................................................................................5
6
Image CRSs with origin in centre of first pixel.......................................................6
7
Image CRSs with origin in corner of first pixel.......................................................8
8
Image datum at pixel centre.....................................................................................9
9
Image datum at pixel corner..................................................................................10
1
Introduction
This change request specifies a standard set of definitions and corresponding URNs that
may be used whenever applicable for unrectified images and other grid coverages. Most
of these definitions are encoded using the GML 3.1.1 Grid CRSs profile specified in
(approved Implementation Specification) OGC 05-096r1.
This change request removes Clause 10 from OGC 05-096r1, in which all of these URNs
were previously specified, and modifies that material for:
a) Corrigenda OGC 06-111 and 06-146 to OGC 05-096r1
b) Comply with recently revised policy document OGC 06-135r7
c) Correct “first pixel” to “corner pixel in the image file with the lowest pixel indices as
defined by that file format”
d) Reverse the order of "row" and "column" axes in a grid CS
e) Specify that the "column" axis is first axis defined by the image-recording format,
and the "row" axis is the second axis defined.
f) More clearly state recommendations for use of these URNs.
These requested URNs are defined for use when it is more effective or efficient to
reference definitions of ImageCRSs and their components using URNs, instead of using
URLs. As specified in Clause 10.3.2 of OWS Common 1.1 (OGC 06-121r3), when a
URL is used to reference a definition:
“When not in the same XML document, those definitions shall be
electronically available over the Internet using this URL, to both
client and server software including multiple clients and multiple
servers that must interoperate. The available definitions shall be
encoded in XML, using … the CRS Schemas in GML”.
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
3
Standard URNs for unrectified image CRSs
URN
urn:ogc:def:cs:OGC:0.0:GridCS2d
urn:ogc:def:axis:OGC:0.0:Row
urn:ogc:def:axis:OGC:0.0:Column
urn:ogc:def:uom:OGC:0.0:GridSpacing
urn:ogc:def:crs:OGC:0.0: ImageCRSpixelCenter:TBD a
urn:ogc:def:crs:OGC:0.0:ImageCRSpixelCorner:TBD a
urn:ogc:def:datum:OGC:0.0:ImageDatumPixelCenter:TBD a
urn:ogc:def:datum:OGC:0.0:ImageDatumPixelCorner:TBD a
Object name & gml:id
OGC 09-108
Definition
specified in
GridCS2d
Row
Column
GridSpacing
ImageCRSpixelCenterTBD
Clause 2
Clause 3
Clause 4
Clause 5
Clause 6
ImageCRSpixelCornerTBD
Clause 7
ImageDatumPixelCenterTBD
Clause 8
ImageDatumPixelCornerTBD
Clause 9
a This “TBD” shall be replaced by the image identifier alphanumeric character string. These image identifier
alphanumeric character string shall be unique.
The first four of these URNs use the format for single objects specified in Subclause 7.1
of “URNs of definitions in ogc namespace” [OGC 07-092r3].The other four of these
URNs use the format for not-completely-specified objects specified in Subclause 7.2 of
[OGC 07-092r3]. These not-completely-specified objects are used because each original
image must have a different ImageCRS and ImageDatum.
NOTE
In general, there may b e a very large number of different original images. As stated in Clause
5.2.7 of Discussion Paper OGC 04-052, a large enterprise may archive on the order of 10,000,000 different
images, and receive on the order of 10,000 new images per day!
2
2D Grid coordinate system
The URN “urn:ogc:def:cs:OGC:0.0:GridCS2d” shall reference the definition of a
Coordinate System for a 2D rectangular grid of grid points. The definition of this grid
coordinate system shall be the same as can be XML encoded using GML 3.1.1 as:
2D grid coordinate system
GridCS2d
A 2D grid coordinate system for use by an image or other
grid coverage. It can be used for a grid of any size, since no grid size
is defined. This coordinate system specifies that each "column"
coordinate value will be listed before the "row" coordinate value. The
grid points are assumed to have the same "grid spacing" in each
direction.
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
4
OGC 09-108
The first "column" axis shall correspond to the pixel index listed first
in the file format definition, and the second "row" axis shall
correspond to the pixel index listed second. This relationship between
the "column and "row" names and the grid point indices shall apply
whether this GridCS2d is associated with a grid file before or after
that file is recorded.
The "column" and "row" axis names are used here although other axis
names may be used by the file format definition, or by the
"scanDirection : Sequence(CharacterString)" attribute of the CV_Grid
class defined in Clause 8 of ISO 19123. Use of other axis names would
require defining different CartesianCSs for other names, or adding other
names as additional axisID values. The XML definitions of the Row and
Column axes includes the alternative axis names "line" and "sample" as
additional axisID values.
(The first row in a grid is sometimes called the "top" row, the first
column is sometimes called the "left" column, and the lowest indices
grid point is then called the "upperLeft" point. However other names can
also be used, since this GridCS2d is defined so that it does not depend
on such left/right, top/bottom, and up/down names.)
This xml document references the two standard grid axes specified below.
3
Row coordinate axis
The URN “urn:ogc:def:axis:OGC:0.0:Row” shall reference the definition of the row
coordinate axis for a 2D grid coordinate system. The definition of this row axis shall be
the same as can be XML encoded using GML 3.1.1 as:
Grid column axis
Column
Sample
For this first "column" grid axis, column coordinate values
match grid column numbers, but allow fractional coordinate values
between grid points. The first column is sometimes called the "left"
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
5
OGC 09-108
column, so the direction of this axis is "right", but these terms are
not required.
C
urn:ogc:def:axisDirection:OGC:1.0:columnPositive
4
Column coordinate axis
The URN “urn:ogc:def:axis:OGC:0.0:Column” shall reference the definition of the
column coordinate axis for a 2D grid coordinate system. The definition of this column
axis shall be the same as can be XML encoded using GML 3.1.1 as:
Grid row axis
Row
Line
For this second "Row" grid axis, row coordinate values match
grid row numbers, but allow fractional coordinate values between grid
points. The first row in a grid is sometimes called the "top" row, so
the direction of this axis is "down", but these terms are not required.
R
urn:ogc:def:axisDirection:OGC:1.0:rowPositive
5
Grid spacing unit of measure
The URN “urn:ogc:def:uom:OGC:0.0:GridSpacing” shall reference the definition of the
grid spacing unit of measure (uom). The definition of this unit shall be the same as can be
XML encoded using GML 3.1.1 as:
Spacing between adjacent grid lines, or between centers of
adjacent pixels
GridSpacing
Length
6
Image CRSs with origin in centre of first pixel
The URN value “urn:ogc:def:crs:OGC:0.0:ImageCRSpixelCenter:TBD” shall reference
the definition of an (unrectified) image CRS with its origin in the centre of the corner
pixel in the image file with the lowest pixel indices as defined by that file format. This
image CRS shall be for the specific image whose alphanumeric character string identifier
is substituted for the “TBD” in this URN.
NOTE 1 This document does not specify any format for an image alphanumeric identifier, since many
different formats are used for such identifiers. However, these image alphanumeric identifiers must be
unique. One such format could concatenate a camera identifier with the image collection date and time.
The definitions of these image CRSs shall be the same as can be XML encoded using
GML 3.1.1 as:
Image TBD CRS pixel centers
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
7
OGC 09-108
TBD
Parameterized definition of 2D image coordinate reference
systems with the origin at the center of the corner pixel in the image
file with the lowest pixel indices as defined by that file format. This
CRS definition can be used for any size image, since no image size is
specified.
This CRS definition is designed to be used for ungeorectified images,
and is not expected to be used for a georectified image. This definition
can be used for a georeferenced or ungeoreferenced image, where a
georeferenced image CRS is associated with the coordinate
Transformation(s) that georeference it.
NOTE 2 It is not expected to be necessary in most cases to produce an XML document that specifies the
image CRS for a specific image identifier, since this CRS definition can be referenced using the specified
URN value with the “TBD” replaced by the specific image identifier. However, it is possible to do this, as
shown in the following example.
EXAMPLE
If this XML document were modified to specify the image CRS with its origin in the centre
of first pixel for an image with the identifier “C543D041201T084027”, this XML document could be:
Image C543D041201T084027 CRS pixel centers
C543D041201T084027
7
Image CRSs with origin in corner of first pixel
The URN value “urn:ogc:def:crs:OGC:0.0:ImageCRSpixelCorner:TBD” shall reference
the definition of an (unrectified) image CRS with its origin in the outside corner of the
corner pixel in the image file with the lowest pixel indices as defined by that file format.
This image CRS shall be for the specific image whose identifier is substituted for the
“TBD” in this URN. Use of this ImageCRS is allowed but is discouraged, since it is not
consistent with ISO 19123.
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
8
OGC 09-108
The definitions of these image CRSs shall be the same as can be XML encoded using
GML 3.1.1 as:
Image TBD CRS pixel corners
TBD
Parameterized definition of 2D image coordinate reference
systems with the origin at the outside corner of the corner pixel in the
image file with the lowest pixel indices as defined by that file format.
This CRS definition can be used for any size image, since no image size
is specified.
This CRS definition is designed to be used for ungeorectified images,
and is not expected to be used for a georectified image. This definition
can be used for a georeferenced or ungeoreferenced image, where a
georeferenced image CRS is associated with the coordinate
Transformation(s) that georeference it.
EXAMPLE
If this XML document were modified to specify the image CRS with its origin in the
outside corner of first pixel for an image with the identifier “C543D041201T084027”, this XML document
could be:
Image C543D041201T084027 CRS pixel corners
C543D041201T084027
8
Image datum at pixel centre
The URN “urn:ogc:def:datum:OGC:0.0:ImageDatumPixelCenter:TBD” shall reference
the definition of an image datum with its origin in the centre of the corner pixel in the
image file with the lowest pixel indices as defined by that file format. This image datum
shall be for the specific image whose alphanumeric character string identifier is
substituted for the “TBD” in this URN. The definition of this image datum shall be the
same as can be XML encoded using GML 3.1.1 as:
Image TBD datum with origin at center of first
pixel
TBD
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
10
OGC 09-108
2D image datum with the origin at the center of the corner
pixel in the image file with the lowest pixel indices.
The origin is the center of the corner pixel with the
lowest indices as defined by the image file format. The pixel index
listed first in the file format definition is used by the first axis in
the coordinate system used with this datum, and the pixel index listed
second is used by the first axis in the coordinate system.
cellCorner
9
Image datum at pixel corner
The URN “urn:ogc:def:datum:OGC:0.0:ImageDatumPixelCorner:TBD” shall reference
the definition of an image datum with its origin at the outside corner of the corner pixel in
the image file with the lowest pixel indices as defined by that file format. This image
datum shall be for the specific image whose alphanumeric character string identifier is
substituted for the “TBD” in this URN. Use of this ImageDatum is discouraged, since it
is not consistent with ISO 19123. The definition of this image datum shall be the same as
can be XML encoded using GML 3.1.1 as:
Image TBD datum with origin at outside corner of first
pixel
TBD
2D image datum with the origin at the outside corner of the
corner pixel in the image file with the lowest pixel indices.
The origin is the outside corner of the corner pixel
with the lowest indices as defined by the image file format. The pixel
index listed first in the file format definition is used by the first
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
11
OGC 09-108
axis in the coordinate system used with this datum, and the pixel index
listed second is used by the first axis in the coordinate system.
cellCorner
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
12
Document OGC 09-108
CR-Form-v3
CHANGE REQUEST
OGC URNs for CR ?
definitions
rev
Current version:
-
For HELP on using this form, see bottom of this page or look at the pop-up text over the symbols.
Proposed change affects:
AS
Imp Spec
Best Practices Paper
Title:
OGN URN change request: Add grid CRS URNs
Source:
Arliss Whiteside and other WCS SWG members
Work item code:
Category:
Other X
Date: 2009-09-09
B (Addition of feature)
Use one of the following categories:
F (Critical correction)
A (corresponds to a correction in an earlier release)
B (Addition of feature),
C (Functional modification of feature)
D (Editorial modification)
Reason for change:
URNs in the “ogc” URN namespace are often effective and efficient for
referencing the definitions of CRSs and their components. A set of these
URNs for ImageCRSs was thus specified in Clause 10 of approved
Implementation Specification OGC 05-096r1 “GML 3.1.1 grid CRSs profile”.
However, those URNs have not yet been accepted by the more-recentlyformed OGC Naming Authority.
Summary of change: Add definitions of eight URNs for definitions of ImageCRSs and their
components, to the registry of URNs approved by the OGC Naming Authority
Consequences if
not approved:
Failure to allow previously specified URNs for ImageCRSs and their
components, some of which are being used with WCS 1.1.
Clauses affected:
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.
1
OGC 09-108
Other specs
X Other core specifications
Affected:
WCS 1.1, GML 3.1.1 grid CRSs profile
Abstract specifications
Best Practices Papers
Supporting Doc.
Other comments:
Status
Disposition
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
2
OGC 09-108
Contents
Page
1
Introduction..............................................................................................................2
2
2D Grid coordinate system......................................................................................3
3
Row coordinate axis.................................................................................................4
4
Column coordinate axis...........................................................................................5
5
Grid spacing unit of measure...................................................................................5
6
Image CRSs with origin in centre of first pixel.......................................................6
7
Image CRSs with origin in corner of first pixel.......................................................8
8
Image datum at pixel centre.....................................................................................9
9
Image datum at pixel corner..................................................................................10
1
Introduction
This change request specifies a standard set of definitions and corresponding URNs that
may be used whenever applicable for unrectified images and other grid coverages. Most
of these definitions are encoded using the GML 3.1.1 Grid CRSs profile specified in
(approved Implementation Specification) OGC 05-096r1.
This change request removes Clause 10 from OGC 05-096r1, in which all of these URNs
were previously specified, and modifies that material for:
a) Corrigenda OGC 06-111 and 06-146 to OGC 05-096r1
b) Comply with recently revised policy document OGC 06-135r7
c) Correct “first pixel” to “corner pixel in the image file with the lowest pixel indices as
defined by that file format”
d) Reverse the order of "row" and "column" axes in a grid CS
e) Specify that the "column" axis is first axis defined by the image-recording format,
and the "row" axis is the second axis defined.
f) More clearly state recommendations for use of these URNs.
These requested URNs are defined for use when it is more effective or efficient to
reference definitions of ImageCRSs and their components using URNs, instead of using
URLs. As specified in Clause 10.3.2 of OWS Common 1.1 (OGC 06-121r3), when a
URL is used to reference a definition:
“When not in the same XML document, those definitions shall be
electronically available over the Internet using this URL, to both
client and server software including multiple clients and multiple
servers that must interoperate. The available definitions shall be
encoded in XML, using … the CRS Schemas in GML”.
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
3
Standard URNs for unrectified image CRSs
URN
urn:ogc:def:cs:OGC:0.0:GridCS2d
urn:ogc:def:axis:OGC:0.0:Row
urn:ogc:def:axis:OGC:0.0:Column
urn:ogc:def:uom:OGC:0.0:GridSpacing
urn:ogc:def:crs:OGC:0.0: ImageCRSpixelCenter:TBD a
urn:ogc:def:crs:OGC:0.0:ImageCRSpixelCorner:TBD a
urn:ogc:def:datum:OGC:0.0:ImageDatumPixelCenter:TBD a
urn:ogc:def:datum:OGC:0.0:ImageDatumPixelCorner:TBD a
Object name & gml:id
OGC 09-108
Definition
specified in
GridCS2d
Row
Column
GridSpacing
ImageCRSpixelCenterTBD
Clause 2
Clause 3
Clause 4
Clause 5
Clause 6
ImageCRSpixelCornerTBD
Clause 7
ImageDatumPixelCenterTBD
Clause 8
ImageDatumPixelCornerTBD
Clause 9
a This “TBD” shall be replaced by the image identifier alphanumeric character string. These image identifier
alphanumeric character string shall be unique.
The first four of these URNs use the format for single objects specified in Subclause 7.1
of “URNs of definitions in ogc namespace” [OGC 07-092r3].The other four of these
URNs use the format for not-completely-specified objects specified in Subclause 7.2 of
[OGC 07-092r3]. These not-completely-specified objects are used because each original
image must have a different ImageCRS and ImageDatum.
NOTE
In general, there may b e a very large number of different original images. As stated in Clause
5.2.7 of Discussion Paper OGC 04-052, a large enterprise may archive on the order of 10,000,000 different
images, and receive on the order of 10,000 new images per day!
2
2D Grid coordinate system
The URN “urn:ogc:def:cs:OGC:0.0:GridCS2d” shall reference the definition of a
Coordinate System for a 2D rectangular grid of grid points. The definition of this grid
coordinate system shall be the same as can be XML encoded using GML 3.1.1 as:
2D grid coordinate system
GridCS2d
A 2D grid coordinate system for use by an image or other
grid coverage. It can be used for a grid of any size, since no grid size
is defined. This coordinate system specifies that each "column"
coordinate value will be listed before the "row" coordinate value. The
grid points are assumed to have the same "grid spacing" in each
direction.
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
4
OGC 09-108
The first "column" axis shall correspond to the pixel index listed first
in the file format definition, and the second "row" axis shall
correspond to the pixel index listed second. This relationship between
the "column and "row" names and the grid point indices shall apply
whether this GridCS2d is associated with a grid file before or after
that file is recorded.
The "column" and "row" axis names are used here although other axis
names may be used by the file format definition, or by the
"scanDirection : Sequence(CharacterString)" attribute of the CV_Grid
class defined in Clause 8 of ISO 19123. Use of other axis names would
require defining different CartesianCSs for other names, or adding other
names as additional axisID values. The XML definitions of the Row and
Column axes includes the alternative axis names "line" and "sample" as
additional axisID values.
(The first row in a grid is sometimes called the "top" row, the first
column is sometimes called the "left" column, and the lowest indices
grid point is then called the "upperLeft" point. However other names can
also be used, since this GridCS2d is defined so that it does not depend
on such left/right, top/bottom, and up/down names.)
This xml document references the two standard grid axes specified below.
3
Row coordinate axis
The URN “urn:ogc:def:axis:OGC:0.0:Row” shall reference the definition of the row
coordinate axis for a 2D grid coordinate system. The definition of this row axis shall be
the same as can be XML encoded using GML 3.1.1 as:
Grid column axis
Column
Sample
For this first "column" grid axis, column coordinate values
match grid column numbers, but allow fractional coordinate values
between grid points. The first column is sometimes called the "left"
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
5
OGC 09-108
column, so the direction of this axis is "right", but these terms are
not required.
C
urn:ogc:def:axisDirection:OGC:1.0:columnPositive
4
Column coordinate axis
The URN “urn:ogc:def:axis:OGC:0.0:Column” shall reference the definition of the
column coordinate axis for a 2D grid coordinate system. The definition of this column
axis shall be the same as can be XML encoded using GML 3.1.1 as:
Grid row axis
Row
Line
For this second "Row" grid axis, row coordinate values match
grid row numbers, but allow fractional coordinate values between grid
points. The first row in a grid is sometimes called the "top" row, so
the direction of this axis is "down", but these terms are not required.
R
urn:ogc:def:axisDirection:OGC:1.0:rowPositive
5
Grid spacing unit of measure
The URN “urn:ogc:def:uom:OGC:0.0:GridSpacing” shall reference the definition of the
grid spacing unit of measure (uom). The definition of this unit shall be the same as can be
XML encoded using GML 3.1.1 as:
Spacing between adjacent grid lines, or between centers of
adjacent pixels
GridSpacing
Length
6
Image CRSs with origin in centre of first pixel
The URN value “urn:ogc:def:crs:OGC:0.0:ImageCRSpixelCenter:TBD” shall reference
the definition of an (unrectified) image CRS with its origin in the centre of the corner
pixel in the image file with the lowest pixel indices as defined by that file format. This
image CRS shall be for the specific image whose alphanumeric character string identifier
is substituted for the “TBD” in this URN.
NOTE 1 This document does not specify any format for an image alphanumeric identifier, since many
different formats are used for such identifiers. However, these image alphanumeric identifiers must be
unique. One such format could concatenate a camera identifier with the image collection date and time.
The definitions of these image CRSs shall be the same as can be XML encoded using
GML 3.1.1 as:
Image TBD CRS pixel centers
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
7
OGC 09-108
TBD
Parameterized definition of 2D image coordinate reference
systems with the origin at the center of the corner pixel in the image
file with the lowest pixel indices as defined by that file format. This
CRS definition can be used for any size image, since no image size is
specified.
This CRS definition is designed to be used for ungeorectified images,
and is not expected to be used for a georectified image. This definition
can be used for a georeferenced or ungeoreferenced image, where a
georeferenced image CRS is associated with the coordinate
Transformation(s) that georeference it.
NOTE 2 It is not expected to be necessary in most cases to produce an XML document that specifies the
image CRS for a specific image identifier, since this CRS definition can be referenced using the specified
URN value with the “TBD” replaced by the specific image identifier. However, it is possible to do this, as
shown in the following example.
EXAMPLE
If this XML document were modified to specify the image CRS with its origin in the centre
of first pixel for an image with the identifier “C543D041201T084027”, this XML document could be:
Image C543D041201T084027 CRS pixel centers
C543D041201T084027
7
Image CRSs with origin in corner of first pixel
The URN value “urn:ogc:def:crs:OGC:0.0:ImageCRSpixelCorner:TBD” shall reference
the definition of an (unrectified) image CRS with its origin in the outside corner of the
corner pixel in the image file with the lowest pixel indices as defined by that file format.
This image CRS shall be for the specific image whose identifier is substituted for the
“TBD” in this URN. Use of this ImageCRS is allowed but is discouraged, since it is not
consistent with ISO 19123.
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
8
OGC 09-108
The definitions of these image CRSs shall be the same as can be XML encoded using
GML 3.1.1 as:
Image TBD CRS pixel corners
TBD
Parameterized definition of 2D image coordinate reference
systems with the origin at the outside corner of the corner pixel in the
image file with the lowest pixel indices as defined by that file format.
This CRS definition can be used for any size image, since no image size
is specified.
This CRS definition is designed to be used for ungeorectified images,
and is not expected to be used for a georectified image. This definition
can be used for a georeferenced or ungeoreferenced image, where a
georeferenced image CRS is associated with the coordinate
Transformation(s) that georeference it.
EXAMPLE
If this XML document were modified to specify the image CRS with its origin in the
outside corner of first pixel for an image with the identifier “C543D041201T084027”, this XML document
could be:
Image C543D041201T084027 CRS pixel corners
C543D041201T084027
8
Image datum at pixel centre
The URN “urn:ogc:def:datum:OGC:0.0:ImageDatumPixelCenter:TBD” shall reference
the definition of an image datum with its origin in the centre of the corner pixel in the
image file with the lowest pixel indices as defined by that file format. This image datum
shall be for the specific image whose alphanumeric character string identifier is
substituted for the “TBD” in this URN. The definition of this image datum shall be the
same as can be XML encoded using GML 3.1.1 as:
Image TBD datum with origin at center of first
pixel
TBD
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
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OGC 09-108
2D image datum with the origin at the center of the corner
pixel in the image file with the lowest pixel indices.
The origin is the center of the corner pixel with the
lowest indices as defined by the image file format. The pixel index
listed first in the file format definition is used by the first axis in
the coordinate system used with this datum, and the pixel index listed
second is used by the first axis in the coordinate system.
cellCorner
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Image datum at pixel corner
The URN “urn:ogc:def:datum:OGC:0.0:ImageDatumPixelCorner:TBD” shall reference
the definition of an image datum with its origin at the outside corner of the corner pixel in
the image file with the lowest pixel indices as defined by that file format. This image
datum shall be for the specific image whose alphanumeric character string identifier is
substituted for the “TBD” in this URN. Use of this ImageDatum is discouraged, since it
is not consistent with ISO 19123. The definition of this image datum shall be the same as
can be XML encoded using GML 3.1.1 as:
Image TBD datum with origin at outside corner of first
pixel
TBD
2D image datum with the origin at the outside corner of the
corner pixel in the image file with the lowest pixel indices.
The origin is the outside corner of the corner pixel
with the lowest indices as defined by the image file format. The pixel
index listed first in the file format definition is used by the first
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
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OGC 09-108
axis in the coordinate system used with this datum, and the pixel index
listed second is used by the first axis in the coordinate system.
cellCorner
Copyright © 2009 Open Geospatial Consortium, Inc. All Rights Reserved.`
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