Class: QgsCoordinateTransformContext¶
-
class
qgis.core.
QgsCoordinateTransformContext
¶ Bases:
sip.wrapper
Constructor for QgsCoordinateTransformContext.
QgsCoordinateTransformContext(rhs: QgsCoordinateTransformContext) Copy constructor
Contains information about the context in which a coordinate transform is executed.
The context stores various information regarding which coordinate operations should be used when transforming points from a source to destination coordinate reference system.
Note
QgsCoordinateTransformContext objects are thread safe for read and write.
Note
QgsCoordinateTransformContext objects are implicitly shared.
See also
See also
New in version 3.0: Enums
Methods
Adds a new
coordinateOperationProjString
to use when projecting coordinates from the specifiedsourceCrs
to the specifieddestinationCrs
.Adds a new
sourceTransform
anddestinationTransform
to use when projecting coordinates from the specifiedsourceCrs
to the specifieddestinationCrs
.Returns the Proj coordinate operation string to use when transforming from the specified
source
CRS todestination
CRS.Returns the pair of source and destination datum transforms to use for a transform from the specified
source
CRS todestination
CRS.Clears all stored transform information from the context.
Returns the stored mapping for source to destination CRS pairs to associated coordinate operation to use (as a proj string).
Returns
True
if the context has a valid coordinate operation to use when transforming from the specifiedsource
CRS todestination
CRS.Reads the context’s state from application settings.
Reads the context’s state from a DOM
element
.Removes the coordinate operation for the specified
sourceCrs
anddestinationCrs
.Removes the source to destination datum transform pair for the specified
sourceCrs
anddestinationCrs
.Returns the stored mapping for source to destination CRS pairs to associated datum transforms to use.
Write the context’s state to application settings.
Writes the context’s state to a DOM
element
.Signals
Attributes
-
addCoordinateOperation
(self, sourceCrs: QgsCoordinateReferenceSystem, destinationCrs: QgsCoordinateReferenceSystem, coordinateOperationProjString: str) → bool¶ Adds a new
coordinateOperationProjString
to use when projecting coordinates from the specifiedsourceCrs
to the specifieddestinationCrs
.coordinateOperationProjString
should be set to a valid Proj coordinate operation string. IfcoordinateOperationProjString
is empty, then the default Proj operation will be used when transforming between the coordinate reference systems.Returns
True
if the new coordinate operation was added successfully.See also
See also
Note
Requires Proj 6.0 or later. Builds based on earlier Proj versions will ignore this setting, and the deprecated addSourceDestinationDatumTransform() method must be used instead.
New in version 3.8.
-
addSourceDestinationDatumTransform
(self, sourceCrs: QgsCoordinateReferenceSystem, destinationCrs: QgsCoordinateReferenceSystem, sourceTransformId: int, destinationTransformId: int) → bool¶ Adds a new
sourceTransform
anddestinationTransform
to use when projecting coordinates from the specifiedsourceCrs
to the specifieddestinationCrs
.If either
sourceTransformId
ordestinationTransformId
is -1, then no datum transform is required for transformations for that source or destination.Returns
True
if the new transform pair was added successfully.See also
Deprecated since version Has: no effect on builds based on Proj 6.0 or later, use addCoordinateOperation() instead.
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calculateCoordinateOperation
(self, source: QgsCoordinateReferenceSystem, destination: QgsCoordinateReferenceSystem) → str¶ Returns the Proj coordinate operation string to use when transforming from the specified
source
CRS todestination
CRS.Returns an empty string if no specific coordinate operation is set for the source to destination pair, in which case the default Proj coordinate operation should be used.
Note
source and destination are reversible.
Note
Requires Proj 6.0 or later. Builds based on earlier Proj versions will always return an empty string, and the deprecated calculateDatumTransforms() method should be used instead.
New in version 3.8.
-
calculateDatumTransforms
(self, source: QgsCoordinateReferenceSystem, destination: QgsCoordinateReferenceSystem) → QgsDatumTransform.TransformPair¶ Returns the pair of source and destination datum transforms to use for a transform from the specified
source
CRS todestination
CRS.Returns an ID of -1 if a datum transform should not be used for the source or destination.
Note
source and destination are reversible.
Deprecated since version Has: no effect on builds based on Proj 6.0 or later. Use calculateCoordinateOperation() instead.
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clear
(self)¶ Clears all stored transform information from the context.
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coordinateOperations
(self) → object¶ Returns the stored mapping for source to destination CRS pairs to associated coordinate operation to use (as a proj string). The map keys will be :py:func:`QgsCoordinateReferenceSystems.authid()`s.
Warning
This method should not be used to calculate the corresponding coordinate operation to use for a coordinate transform. Instead, always use calculateCoordinateOperation() to determine this.
See also
Note
Requires Proj 6.0 or later. Builds based on earlier Proj versions will always return an empty list, and the deprecated sourceDestinationDatumTransforms() method must be used instead.
New in version 3.8.
-
hasTransform
(self, source: QgsCoordinateReferenceSystem, destination: QgsCoordinateReferenceSystem) → bool¶ Returns
True
if the context has a valid coordinate operation to use when transforming from the specifiedsource
CRS todestination
CRS.Note
source and destination are reversible.
-
readSettings
(self)¶ Reads the context’s state from application settings.
See also
-
readXml
(self, element: QDomElement, context: QgsReadWriteContext) → Tuple[bool, List[str]]¶ Reads the context’s state from a DOM
element
.Returns
False
if transforms stored in the XML are not available. In this casemissingTransforms
will be filled with missing datum transform strings.See also
-
removeCoordinateOperation
(self, sourceCrs: QgsCoordinateReferenceSystem, destinationCrs: QgsCoordinateReferenceSystem)¶ Removes the coordinate operation for the specified
sourceCrs
anddestinationCrs
.New in version 3.8.
-
removeSourceDestinationDatumTransform
(self, sourceCrs: QgsCoordinateReferenceSystem, destinationCrs: QgsCoordinateReferenceSystem)¶ Removes the source to destination datum transform pair for the specified
sourceCrs
anddestinationCrs
.See also
Deprecated since version Use: removeCoordinateOperation() instead
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sourceDestinationDatumTransforms
(self) → object¶ Returns the stored mapping for source to destination CRS pairs to associated datum transforms to use. The map keys will be :py:func:`QgsCoordinateReferenceSystems.authid()`s.
If either the source transform ID or destination transform ID is -1, then no datum transform is required for transformations for that source or destination.
Warning
This method should not be used to calculate the corresponding datum transforms to use for a coordinate transform. Instead, always use calculateDatumTransforms() to determine this.
See also
Deprecated since version Has: no effect on builds based on Proj 6.0 or later, use coordinateOperations() instead.
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writeSettings
(self)¶ Write the context’s state to application settings.
See also
-