Reprojection Node

With geospatial or map data, two of the most common ways that are used to identify coordinates are projected coordinate and geographic coordinate systems. Within IBM® SPSS® Modeler, items such as the Expression Builder spatial functions, the Spatio-Temporal Prediction (STP) Node, and the Map Visualization Node use the projected coordinate system and therefore any data that you import that is recorded with a geographic coordinate system must be reprojected. Where possible, geospatial fields (any fields with a geospatial measurement level) are automatically reprojected when used (not when they are imported). Where any fields cannot be reprojected automatically you use the Reproject node to change their coordinate system. Reprojecting in this way means that you can correct situations where an error occurs due to use of an incorrect coordinate system.

Example situations where you might have to reproject to change the coordinate system are shown in the following list:

  • Append If you try to append two data sets with different coordinate systems for a geospatial field SPSS Modeler displays the following error message:Coordinate systems of <Field1> and <Field2> are not compatible. Reproject one or both fields to the same coordinate system.

    <Field1> and <Field2> are the names of the geospatial fields that caused the error.

  • If/else expression If you use an expression that contains an if/else statement with geospatial fields or return types in both parts of the expression, but with different coordinate systems, SPSS Modeler displays the following error message: The conditional expression contains incompatible coordinate systems: <arg1> and <arg2>.

    <arg1> and <arg2> are the then or else arguments that return a geospatial type with different coordinate systems.

  • Constructing a list of geospatial fields To create a list field that consists of numerous geospatial fields, all geospatial field arguments that are supplied to the list expression must be in the same coordinate system. If they are not, then the following error message is displayed: Coordinate systems of <Field1> and <Field2> are not compatible. Reproject one or both fields to the same coordinate system.

For more information about coordinate systems, see Setting geospatial options for streams.