Performing an AEC Transform

When data in a model uses a Geographic Coordinate System, MicroStation can easily reference data that is also geographically aware into the model. While attaching an iModel, in MicroStation, if both the reference iModel and the active model have a GCS, the Attach iModel as Reference dialog enables the AEC Transform icon.

The AEC Transform option in the Attach iModel as Reference dialog, Select Model section, will perform an AEC Transform to align the GCSs in the iModel and the active model during attachment.

Note: the AEC Transform option will be enabled only if both the reference iModel and the active model have a GCS. If both or either of the model is missing GCS information, this option will not be enabled. If both the reference iModel and the active model have the same GCS then an AEC Transform is not needed.

With an AEC transform, MicroStation calculates the linear transformation to give the best approximation to the results. The approximation is acceptable for smaller-scale data, such as most man-made structures that occupy less than a square kilometer.

With the reference model and the active model GCSs aligned it will be easier to place and manipulate elements in a relative coordinate system.

Note: AEC Transform will also work for iModels with a GCS with Helmert transformation in the coordinate system.

Current iModel attachments do not recognize project North rotations. If there is a project North setup then the attached iModel can be aligned to the project north instead of True North using an AEC Transform during attachment.

With an AEC transformation applied in the references dialog for the selected iModel reference you will see Orientation as Geographic - AEC Transform.

Without an AEC Transform the iModel will not be referenced with the correct geolocation and the orientation of the iModel reference will be Coincident.