Module com.esri.arcgisruntime
Package com.esri.arcgisruntime.geometry

Class DatumTransformation

java.lang.Object
com.esri.arcgisruntime.geometry.DatumTransformation
Direct Known Subclasses:
GeographicTransformation, HorizontalVerticalTransformation
public abstract class DatumTransformation extends Object
Represents a function to convert between the coordinate systems. This is the base class for classes used to transform coordinates between spatial references that have different datums. The inverse of the datum transformation, used to transform in the opposite direction, may be accessed by calling getInverse().

A datum transformation has a getName() method, which returns a name suitable for display, such as when displaying a list of available transformations to an end user.

You can get a list of suitable transformations for a given input and output spatial reference by using the TransformationCatalog.getTransformationsBySuitability method. Alternatively, if you know the transformations you require, create a GeographicTransformation from one or more GeographicTransformationSteps. The following example shows a GeographicTransformation created with a single GeographicTransformationStep: 

 // Create a geometry located in London, UK, with British National Grid spatial reference
 Point britishNationalGridPt = new Point(538985.355, 177329.516, SpatialReference.create(27700));
 // Create a GeographicTransformation with a single step using WKID for OSGB_1936_To_WGS_1984_NGA_7PAR transformation
 GeographicTransformation transform = GeographicTransformation.create(GeographicTransformationStep.create(108336));
 // Project the point to WGS84, using the transformation
 Point wgs84Pt = (Point) GeometryEngine.project(britishNationalGridPt, SpatialReferences.getWgs84(), transform);

To transform coordinates in the opposite direction (from the output spatial reference to the input spatial reference using the same transformation methods, use the getInverse() method. 

 // Create a geometry located in London UK, with British National Grid spatial reference
 Point britishNationalGridPt = new Point(538985.355, 177329.516, SpatialReference.create(27700));

 // Create a transformation with more than one step
 List<GeographicTransformationStep> steps = new ArrayList<>();
 steps.add(GeographicTransformationStep.create(1196)); // OSGB_1936_To_WGS_1984_2
 steps.add(GeographicTransformationStep.create(1149).getInverse()); // ETRS_1989_To_WGS_1984 inversed
 GeographicTransformation transform = GeographicTransformation.create(steps);

 // Project the point to ETRS 1989 geographic spatial reference, using the transformation
 Point etrs89Pt = (Point) GeometryEngine.project(britishNationalGridPt, SpatialReference.create(4258), transform);

Some geographic transformations require that certain Projection Engine data files be present on the local file system. Call isMissingProjectionEngineFiles() to determine if any of the files are missing; if true, then the transformation cannot be used to project geometries. The complete list of necessary files is available by calling the GeographicTransformationStep.getProjectionEngineFilenames() on each geographic transformation step.

In order for any Projection Engine files to be found, the data location must be set first using the TransformationCatalog.setProjectionEngineDirectory(String) method.

A datum transformation object is immutable.

Since:
100.2.0
See Also:

  • Method Details

    • getName

      public String getName()
      Gets the name of the datum transformation, suitable for display in a user interface.

      If this transformation has more than one step, the name contains the concatenated names of each step's transformation, separated by a plus sign '+'. If the transformation is inverted, the name starts with a tilde (~).

      Returns:
      the name of the datum transformation
      Since:
      100.2.0

    • getInputSpatialReference

      public SpatialReference getInputSpatialReference()
      Gets the input spatial reference of this datum transformation. This transformation is suitable for transforming geometries whose spatial reference has the same datum as this spatial reference.
      Returns:
      the input spatial reference
      Since:
      100.2.0

    • getOutputSpatialReference

      public SpatialReference getOutputSpatialReference()
      Gets the output spatial reference of this datum transformation. This transformation is suitable for transforming geometries into a spatial reference that has the same datum as this spatial reference.
      Returns:
      the output spatial reference
      Since:
      100.2.0

    • getInverse

      public abstract DatumTransformation getInverse()
      Gets the inverse of this datum transformation.
      Returns:
      the inverse of this datum transformation, or null if the transformation is not invertible
      Since:
      100.2.0

    • isMissingProjectionEngineFiles

      public boolean isMissingProjectionEngineFiles()
      Indicates if any files needed by the Projection Engine for any of the geographic transformation steps that comprise this transformation are missing from the local file system.

      If true, this indicates that this transformation is not currently usable; in this case, using the GeometryEngine.project(Geometry, SpatialReference, DatumTransformation) method with this transform will throw an exception. In order for a transform to be usable, two conditions must be satisfied:

      If Projection Engine files are installed at run time, the app may need to be restarted for this value to change.

      If false, this transformation can successfully be used. Either this transformation does not require any Projection Engine files (it is equation-based), or the required files are found.

      Returns:
      true if any required files are missing; false otherwise
      Since:
      100.2.0

    • equals

      public boolean equals(Object obj)
      Tests if this object is equal to a second DatumTransformation object. Returns true if the two DatumTransformations use the same methods of transformation, and operate in the same direction.
      Overrides:
      equals in class Object
      Parameters:
      obj - the reference DatumTransformation with which to compare
      Returns:
      true if the comparison succeeds and the objects are equal, false otherwise
      Since:
      100.2.0

    • hashCode

      public int hashCode()
      Generates a hash value from the DatumTransformation.
      Overrides:
      hashCode in class Object
      Returns:
      a hash value based on the current DatumTransformation
      Since:
      100.2.0