How to encode coordinate operation definitions. Builds on referenceSystems.xsd to
encode the data needed to define coordinate operations, including Transformations,
Conversions, and other specific subtypes of operations.
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This schema encodes the Coordinate Operation (CC_) package of the extended UML Model for OGC
Abstract Specification Topic 2: Spatial Referencing by Coordinates. That UML model is adapted
from ISO 19111 - Spatial referencing by coordinates, as described in Annex C of Topic 2.
Caution: The CRS package in GML 3.1 and GML 3.1.1 is preliminary, and is expected to undergo
some modifications that are not backward compatible during the development of GML 3.2 (ISO
19136). The GML 3.2 package will implement the model described in the revised version of ISO
19111.
Basic encoding for coordinate operation objects, simplifying and restricting
the DefinitionType as needed.
The name by which this coordinate operation is identified.
A mathematical operation on coordinates that transforms or converts coordinates
to another coordinate reference system. Many but not all coordinate operations (from CRS A
to CRS B) also uniquely define the inverse operation (from CRS B to CRS A). In some cases,
the operation method algorithm for the inverse operation is the same as for the forward
algorithm, but the signs of some operation parameter values must be reversed. In other
cases, different algorithms are required for the forward and inverse operations, but the
same operation parameter values are used. If (some) entirely different parameter values are
needed, a different coordinate operation shall be defined.
Set of alternative identifications of this coordinate operation. The
first coordinateOperationID, if any, is normally the primary identification code,
and any others are aliases.
Comments on or information about this coordinate operation, including
source information.
Unordered set of estimates of the impact of this coordinate operation
on point position accuracy. Gives position error estimates for target coordinates of
this coordinate operation, assuming no errors in source coordinates.
An identification of a coordinate operation.
Version of the coordinate transformation (i.e., instantiation due to the
stochastic nature of the parameters). Mandatory when describing a transformation, and should
not be supplied for a conversion.
Association to the source CRS (coordinate reference system) of this coordinate
operation.
Association to the target CRS (coordinate reference system) of this coordinate
operation. For constraints on multiplicity of "sourceCRS" and "targetCRS", see UML model of
Coordinate Operation package in OGC Abstract Specification topic 2.
Association to a coordinate operation, either referencing or containing the
definition of that coordinate operation.
An ordered sequence of two or more single coordinate operations. The sequence
of operations is constrained by the requirement that the source coordinate reference system
of step (n+1) must be the same as the target coordinate reference system of step (n). The
source coordinate reference system of the first step and the target coordinate reference
system of the last step are the source and target coordinate reference system associated
with the concatenated operation. Instead of a forward operation, an inverse operation may be
used for one or more of the operation steps mentioned above, if the inverse operation is
uniquely defined by the forward operation.
Ordered sequence of associations to the two or more single operations
used by this concatenated operation.
Association to a single operation.
Association to a concatenated operation, either referencing or containing the
definition of that concatenated operation.
A single (not concatenated) coordinate operation.
Association to a single operation, either referencing or containing the
definition of that single operation.
A pass-through operation specifies that a subset of a coordinate tuple is
subject to a specific coordinate operation.
Ordered sequence of positive integers defining the positions in a
coordinate tuple of the coordinates affected by this pass-through operation.
A positive integer defining a position in a coordinate tuple.
Association to the operation applied to the specified ordinates.
Association to a pass through operation, either referencing or containing the
definition of that pass through operation.
A parameterized mathematical operation on coordinates that transforms or
converts coordinates to another coordinate reference system. This coordinate operation uses
an operation method, usually with associated parameter values. However, operation methods
and parameter values are directly associated with concrete subtypes, not with this abstract
type.
This abstract complexType shall not be directly used, extended, or restricted in a compliant
Application Schema.
Association to an abstract operation, either referencing or containing the
definition of that operation.
An abstract operation on coordinates that does not include any change of datum.
The best-known example of a coordinate conversion is a map projection. The parameters
describing coordinate conversions are defined rather than empirically derived. Note that
some conversions have no parameters.
This abstract complexType is expected to be extended for well-known operation methods with
many Conversion instances, in Application Schemas that define operation-method-specialized
element names and contents. This conversion uses an operation method, usually with
associated parameter values. However, operation methods and parameter values are directly
associated with concrete subtypes, not with this abstract type. All concrete types derived
from this type shall extend this type to include a "usesMethod" element that references the
"OperationMethod" element. Similarly, all concrete types derived from this type shall extend
this type to include zero or more elements each named "uses...Value" that each use the type
of an element substitutable for the "_generalParameterValue" element.
Association to a general conversion, either referencing or containing the
definition of that conversion.
A concrete operation on coordinates that does not include any change of Datum.
The best-known example of a coordinate conversion is a map projection. The parameters
describing coordinate conversions are defined rather than empirically derived. Note that
some conversions have no parameters.
This concrete complexType can be used with all operation methods, without using an
Application Schema that defines operation-method-specialized element names and contents,
especially for methods with only one Conversion instance.
Unordered list of composition associations to the set of parameter
values used by this conversion operation.
Association to the operation method used by this coordinate operation.
Composition association to a parameter value used by this coordinate
operation.
Association to a concrete general-purpose conversion, either referencing or
containing the definition of that conversion.
An abstract operation on coordinates that usually includes a change of Datum.
The parameters of a coordinate transformation are empirically derived from data containing
the coordinates of a series of points in both coordinate reference systems. This
computational process is usually "over-determined", allowing derivation of error (or
accuracy) estimates for the transformation. Also, the stochastic nature of the parameters
may result in multiple (different) versions of the same coordinate transformation.
This abstract complexType is expected to be extended for well-known operation methods with
many Transformation instances, in Application Schemas that define
operation-method-specialized value element names and contents. This transformation uses an
operation method with associated parameter values. However, operation methods and parameter
values are directly associated with concrete subtypes, not with this abstract type. All
concrete types derived from this type shall extend this type to include a "usesMethod"
element that references one "OperationMethod" element. Similarly, all concrete types derived
from this type shall extend this type to include one or more elements each named
"uses...Value" that each use the type of an element substitutable for the
"_generalParameterValue" element.
Association to a general transformation, either referencing or containing the
definition of that transformation.
A concrete operation on coordinates that usually includes a change of datum.
The parameters of a coordinate transformation are empirically derived from data containing
the coordinates of a series of points in both coordinate reference systems. This
computational process is usually "over-determined", allowing derivation of error (or
accuracy) estimates for the transformation. Also, the stochastic nature of the parameters
may result in multiple (different) versions of the same coordinate transformation.
This concrete complexType can be used for all operation methods, without using an
Application Schema that defines operation-method-specialized element names and contents,
especially for methods with only one Transformation instance.
Unordered set of composition associations to the set of parameter
values used by this transformation operation.
Association to a transformation, either referencing or containing the
definition of that transformation.
Abstract parameter value or group of parameter values.
This abstract complexType is expected to be extended and restricted for well-known operation
methods with many instances, in Application Schemas that define operation-method-specialized
element names and contents. Specific parameter value elements are directly contained in
concrete subtypes, not in this abstract type. All concrete types derived from this type
shall extend this type to include one "...Value" element with an appropriate type, which
should be one of the element types allowed in the ParameterValueType. In addition, all
derived concrete types shall extend this type to include a "valueOfParameter" element that
references one element substitutable for the "OperationParameter" element.
A parameter value, ordered sequence of values, or reference to a file of
parameter values. This concrete complexType can be used for operation methods without using
an Application Schema that defines operation-method-specialized element names and contents,
especially for methods with only one instance. This complexType can be used, extended, or
restricted for well-known operation methods, especially for methods with many instances.
Numeric value of an operation parameter, with its associated unit of measure.
Value of an angle operation parameter, in either degree-minute-second format or
single value format.
String value of an operation parameter. A string value does not have an
associated unit of measure.
Positive integer value of an operation parameter, usually used for a count. An
integer value does not have an associated unit of measure.
Boolean value of an operation parameter. A Boolean value does not have an
associated unit of measure.
Ordered sequence of two or more numeric values of an operation parameter list,
where each value has the same associated unit of measure. An element of this type contains a
space-separated sequence of double values.
Ordered sequence of two or more integer values of an operation parameter list,
usually used for counts. These integer values do not have an associated unit of measure. An
element of this type contains a space-separated sequence of integer values.
Reference to a file or a part of a file containing one or more parameter
values, each numeric value with its associated unit of measure. When referencing a part of a
file, that file must contain multiple identified parts, such as an XML encoded document.
Furthermore, the referenced file or part of a file can reference another part of the same or
different files, as allowed in XML documents.
Association to the operation parameter that this is a value of.
A group of related parameter values. The same group can be repeated more than
once in a Conversion, Transformation, or higher level parameterValueGroup, if those
instances contain different values of one or more parameterValues which suitably distinquish
among those groups. This concrete complexType can be used for operation methods without
using an Application Schema that defines operation-method-specialized element names and
contents, especially for methods with only one instance. This complexType can be used,
extended, or restricted for well-known operation methods, especially for methods with many
instances.
Unordered set of composition associations to the parameter values and
groups of values included in this group.
A composition association to a parameter value or group of values included in
this group.
Association to the operation parameter group for which this element provides
parameter values.
Basic encoding for operation method objects, simplifying and restricting the
DefinitionType as needed.
The name by which this operation method is identified.
Definition of an algorithm used to perform a coordinate operation. Most
operation methods use a number of operation parameters, although some coordinate conversions
use none. Each coordinate operation using the method assigns values to these parameters.
Set of alternative identifications of this operation method. The first
methodID, if any, is normally the primary identification code, and any others are
aliases.
Comments on or information about this operation method, including
source information.
Unordered list of associations to the set of operation parameters and
parameter groups used by this operation method.
An identification of an operation method.
Formula(s) used by this operation method. The value may be a reference to a
publication. Note that the operation method may not be analytic, in which case this element
references or contains the procedure, not an analytic formula.
Number of dimensions in the source CRS of this operation method.
Number of dimensions in the target CRS of this operation method.
Association to an operation parameter or parameter group used by this operation
method.
Association to a concrete general-purpose operation method, either referencing
or containing the definition of that method.
Abstract definition of a parameter or group of parameters used by an operation
method.
The minimum number of times that values for this parameter group or parameter
are required. If this attribute is omitted, the minimum number is one.
Association to an operation parameter or group, either referencing or
containing the definition of that parameter or group.
Basic encoding for operation parameter objects, simplifying and restricting the
DefinitionType as needed.
The name by which this operation parameter is identified.
The definition of a parameter used by an operation method. Most parameter
values are numeric, but other types of parameter values are possible. This complexType is
expected to be used or extended for all operation methods, without defining
operation-method-specialized element names.
Set of alternative identifications of this operation parameter. The
first parameterID, if any, is normally the primary identification code, and any
others are aliases.
Comments on or information about this operation parameter, including
source information.
An identification of an operation parameter.
Association to an operation parameter, either referencing or containing the
definition of that parameter.
Basic encoding for operation parameter group objects, simplifying and
restricting the DefinitionType as needed.
The name by which this operation parameter group is identified.
The definition of a group of parameters used by an operation method. This
complexType is expected to be used or extended for all applicable operation methods, without
defining operation-method-specialized element names.
Set of alternative identifications of this operation parameter group.
The first groupID, if any, is normally the primary identification code, and any
others are aliases.
Comments on or information about this operation parameter group,
including source information.
Unordered list of associations to the set of operation parameters that
are members of this group.
An identification of an operation parameter group.
The maximum number of times that values for this parameter group can be
included. If this attribute is omitted, the maximum number is one.
Association to an operation parameter that is a member of a group.
Association to an operation parameter, either referencing or containing the
definition of that parameter.