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 transforms should be used when transforming points from a source to destination coordinate reference system.

The highest priority transforms are those set using addSourceDestinationDatumTransform() and which the transform has a matching source to destination CRS pair.

Failing this, if the source CRS has a matching transform specified by addSourceDatumTransform() then this datum transform will be used. The same logic applies for destination CRS transforms set using addDestinationDatumTransform().

Note

QgsCoordinateTransformContext objects are thread safe for read and write.

Note

QgsCoordinateTransformContext objects are implicitly shared.

New in version 3.0: Enums

Methods

addSourceDestinationDatumTransform

Adds a new sourceTransform and destinationTransform to use when projecting coordinates from the specified sourceCrs to the specified destinationCrs.

calculateDatumTransforms

Returns the pair of source and destination datum transforms to use for a transform from the specified source CRS to destination CRS.

clear

Clears all stored transform information from the context.

hasTransform

Returns True if the context has a valid datum transform to use when transforming from the specified source CRS to destination CRS.

readSettings

Reads the context’s state from application settings.

readXml

Reads the context’s state from a DOM element.

removeSourceDestinationDatumTransform

Removes the source to destination datum transform pair for the specified sourceCrs and destinationCrs.

sourceDestinationDatumTransforms

Returns the stored mapping for source to destination CRS pairs to associated datum transforms to use.

writeSettings

Write the context’s state to application settings.

writeXml

Writes the context’s state to a DOM element.

Signals

Attributes

addSourceDestinationDatumTransform(self, sourceCrs: QgsCoordinateReferenceSystem, destinationCrs: QgsCoordinateReferenceSystem, sourceTransformId: int, destinationTransformId: int) → bool

Adds a new sourceTransform and destinationTransform to use when projecting coordinates from the specified sourceCrs to the specified destinationCrs.

If either sourceTransformId or destinationTransformId 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.

Note

Transforms set using this method will override any specific source or destination transforms set by addSourceDatumTransform() or addDestinationDatumTransform().

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 to destination 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.

clear(self)

Clears all stored transform information from the context.

hasTransform(self, source: QgsCoordinateReferenceSystem, destination: QgsCoordinateReferenceSystem) → bool

Returns True if the context has a valid datum transform to use when transforming from the specified source CRS to destination CRS.

Note

source and destination are reversible.

readSettings(self)

Reads the context’s state from application settings.

See also

readSettings()

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 case missingTransforms will be filled with missing datum transform strings.

See also

writeXml()

removeSourceDestinationDatumTransform(self, sourceCrs: QgsCoordinateReferenceSystem, destinationCrs: QgsCoordinateReferenceSystem)

Removes the source to destination datum transform pair for the specified sourceCrs and destinationCrs.

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.

writeSettings(self)

Write the context’s state to application settings.

See also

writeSettings()

writeXml(self, element: QDomElement, context: QgsReadWriteContext)

Writes the context’s state to a DOM element.

See also

readXml()