# HorizontalVerticalTransformation

Used to transform coordinates of z-aware geometries between spatial references that have different geographic and/or vertical coordinate systems. A HorizontalVerticalTransformation is an ordered list of HorizontalVerticalTransformationStep objects. Each HorizontalVerticalTransformation has an input and an output SpatialReference, and this HorizontalVerticalTransformation object can be used to convert coordinates between the horizontal (geographic) and vertical datums of these spatial references using the series of steps it contains. Use the GeometryEngine.projectOrNull(Geometry, SpatialReference, DatumTransformation) method to transform the coordinates of a specific Geometry.

A horizontal transformation step is not needed when the input and output spatial references have the same underlying geographic coordinate systems. A vertical transformation is not needed if both datums (for ellipsoidal heights) or vertical datums (for gravity-related heights) are the same. To transform coordinates only between different horizontal (geographic) coordinate systems, you can use a GeographicTransformation instead.

The inverse of this transformation, used to transform in the opposite direction, is returned from the DatumTransformation.getInverseOrNull() method.

A HorizontalVerticalTransformation can be constructed from a single HorizontalVerticalTransformationStep object, or from a number of transformation step objects that are chained together.

You can get a list of suitable transformations for a given input and output spatial reference using one of the methods on the TransformationCatalog class.

Some transformations require that certain Projection Engine data files be present on the local file system, and vertical transformation steps are especially likely to use such files, which can be very large in size. The DatumTransformation.isMissingProjectionEngineFiles property indicates whether any of the files are missing. The complete list of necessary files for each specific step is available using the HorizontalVerticalTransformationStep.projectionEngineFilenames property.

A HorizontalVerticalTransformation object is immutable.

#### Since

200.1.0

#### See also

## Constructors

Create a multi-step transformation from one or more HorizontalVerticalTransformationStep instances. Use this constructor to create a horizontal-vertical transformation that has multiple steps. The output SpatialReference of each step should match the input SpatialReference of the following step.

Create a single step transformation.