Transform Job, Import/Export Transformations
The Select Transformation window is displayed to perform point transformation or conversion operations when one of the following options is selected:
The function is otherwise identical in each case with operational differences noted further below, however the following details are primarily with reference to the Transform Job option.
|When Geoida is running, details of the purpose and use of each control in this window will be displayed in the bottom panel when the mouse is passed over any active object.|
With this option, the Test button will be enabled (when a matching transformation has been selected) so that the results of the transformation can be inspected before committing the transaction so that it may be accepted if satisfactory or rejected and abandoned if not. A test may fail for a number of reasons depending on the type of transformation used - common reasons may be, for example, points without valid heights (eg, 3D similarity or Molodensky transformations or where a height datum is converted between geoidal and spheroidal and no geoid-spheroid separation has been specified), or non-adjacent zone numbers for Zone-to-Zone transformations.
Note - the Test function is not available when the Select Transformation window is loaded from the Import or List Points / Export options.
Although it is possible to override the Matching-only radio button and change it to Show all transformations, unless the datums for any subsequently-selected transformation match the current job (either in-to or out-of), the Compute or Test buttons will NOT be enabled to prevent serious errors being made. Also, the Target coordinate system options will be enabled and set ONLY when the Compute button is enabled and the datums match.
The transformation not only converts the point coordinates to the new datum, but if appropriate, also modifies the job configuration, the changes to which will then be seen in the Job Configuration option. A simple Linear/Affine transformation will not result in changes to the job configuration as there are no datum or coordinate type changes.
|IMPORTANT - ALWAYS verify the accuracy and reliability of a transformation before applying to critical data - always test first with points whose coordinates are known in both systems.|
Job coordinate type conversion
To convert a job between one coordinate type and the other on the same datum, refer to Coordinate-type conversion in Job Configuration. This is not the same as the Transform Job option; note that simply changing the horizontal datum in Job Configuration also does not transform the job.
Refer to the Definitions menu Transformations option and the Data Transformations - General topic and sub-topics for additional information.
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