Coordinate Transformation wizard page enables feature geometry re-projection from data source file's coordinate system to drawing coordinate system:

Import Features wizard Coordinate Transformation page

This wizard page provides following options:

• Flatten feature geometry to 2D - if checked, forces any imported feature geometry to 2D.
• Disable feature coordinate transformation - If checked, disables feature coordinate transformation.
• Source spatial reference system - represents coordinate system found in specified source data file (if any).
• Target spatial reference system - represents default coordinate system of the current drawing.

It also provides following navigation buttons:

• Previous - returns to Specifying Data Source File wizard page.
• Next - proceeds to Specifying Feature Transformation wizard page.
• Cancel - exits this wizard and closes the dialog.
• Help - displays this help page.

Specifying Spatial Reference System

Spatial reference system (SRS) or coordinate reference system (CRS) is a coordinate-based local, regional or global system used to locate geographical entities. A spatial reference system defines a specific map projection, as well as transformations between different spatial reference systems. If coordinate transformation is not disabled, it is possible to set both source (external data file's) and target (current drawing's) coordinate systems, thus providing parameters for feature geometry coordinate transformation.

Feature Import wizard first queries selected external data file for spatial reference system. If query succeeds, the Source spatial reference system field is populated, and selecting different one is disabled. If querying does not succeed, meaning that external file does not carry spatial reference systems information, it is necessary to specify one by clicking on button next to the source spatial reference system name:

Coordinate Reference System dialog