Vertical Offset

A Vertical Offset transformation requires the creation of a Vertical Transformation with the type 'Vertical Offset', to convert between two different Vertical Coordinate Systems. There are a number of pre-defined objects in the Datasource, but it is also possible for users to define their own Vertical Offset transformations.

Object Definitions for Vertical Offset

Setting up object definitions for a Vertical Offset transformation from Vertical Coordinate System A (in linear unit C) to Vertical Coord Sys B (in linear unit D) requires the following:

  1. Ensure that Vertical Coordinate Systems "A" and "B" are in the Datasource.
  2. Create a new Vertical Transform "A to B" to represent the conversion from Vertical Coordinate System A to Vertical Coordinate System B. The Method should be "Vertical Offset."   
  3. The offset parameter should be set with the desired offset value and with units D.

Performing a Vertical Offset Transformation

To perform a Vertical Offset Transformation from Vertical Coordinate System A (in linear unit C) to Vertical Coordinate System B (in linear unit D) perform the following steps:

  1. Set up an interactive conversion with a Source horizontal Coordinate System (for example, WGS84) and Source vertical of "A". Set a Target horizontal Coordinate System (for example, WGS84) and Target vertical of "B."  
  2. Enter a height value (which should be in units "C") as part of the Source Coordinate Point Definition.  
  3. Clicking Calculate should prompt you to select a Vertical Transformation to convert from A to B, and should include "A to B" in the choices. If you select this transformation, the transformed point should have a  height value in units "D".

Vertical Offset and Slope Transformation

A Vertical Offset and Slope transformation requires the creation of a Vertical Transformation with the method 'Vertical Offset and Slope', to convert between two different Vertical Coordinate Systems. There are a number of pre-defined objects in the Datasource, but it is also possible for users to define their own Vertical Offset and Slope transformations.

Note on transformation parameters: The ordinate points are a test for the system provided by an issuing authority, and not used in the calculation.

"Ordinate 1 of evaluation point" is the 0 latitude of the "Inclination in latitude" slope.

"Ordinate 2 of evaluation point" is the 0 longitude of the "Inclination in longitude" slope.

The semi-major and minor axis are the parameters used for the base ellipsoid.

Object Definitions for Vertical Offset and Slope

Setting object definitions for a Vertical Offset and Slope transformation from Vertical Coordinate System A (in linear unit C) to Vertical Coord Sys B (in linear unit D) requires the following:

  1. Ensure that Vertical Coordinate Systems "A" and "B" are in the Datasource.
  2. Create a new Vertical Transform "A to B" to represent the conversion from Vertical
  3. Coordinate System A to Vertical Coordinate System B. The Method should be "Vertical Offset and Slope."

The offset and slope parameters should be set with the desired offset value and with units D.

Performing a Vertical Offset and Slope Transformation

To perform a Vertical Offset Transformation from Vertical Coordinate System A (in linear unit C) to Vertical Coordinate System B (in linear unit D) perform the following steps:

  1. Set up an interactive conversion with a Source horizontal Coordinate System (for example, WGS84) and Source vertical of "A". Set a Target horizontal Coordinate System (for example, WGS84) and Target vertical of "B."
  2. Enter a height value (which should be in units "C") as part of the Source Coordinate Point Definition.
  3. Clicking Calculate should prompt you to select a Vertical Transformation to convert from A to B, and should include "A to B" in the choices. If you select this transformation, the transformed point should have a  height value in units "D.