Lab III Section I: Coordinate Conversion of Map Files

Objective: To convert the coordinate system of a vector map file from Latitude Longitude to Mercator world projection.

Data: ESRI Shape File

The Geographic Calculator has the ability to convert coordinate systems within vector map files. The Geographic Calculator Map File Conversion function supports the following map file types:

To successfully complete a Map File Conversion, the coordinate system of the original map file must be known. A coordinate conversion that does not have accurate input coordinate system information will not yield accurate results.

Follow these steps to convert the coordinate system of a vector map file:

  1. Open the Geographic Calculator and click the Map File Conversions job.

  2. Open the Map File for your conversion by going to the File Conversion Settings area and clicking on the Add Files button.

  3. In the open file dialog that appears browse to the directory where the Getting Started Guide installed its data and select WorldCountries.shp

    The Calculator will detect the coordinate system for the shape file because it has an attached PRJ file.  Not all files will have a projection defined with them.  

  4. In the File Conversions Settings area check the Use output filename prefix check box. This will automatically assign an "out_" prefix to the input filename, thereby creating a unique output file name.

  5. In the File Conversions Settings area check the Use specific output directory check box and choose the save-to location for your output files.  Select to save your output files back to the Getting Started Guide data folder.

NOTE: The filetype IN must be the same as the filetype OUT. For example, if the source file is a *.shp file, the output file must be of type *.shp. For this exercise, the output file name should be Out_WorldCountries.shp .

  1. In the File Conversions Settings area click the Auto Generate control button. This will place the output path and filename in the output file box.

  2. To select the output coordinate system, double-click on the blue box labeled System in the Coordinate System area at the bottom right of Map File job.  By default, the Calculator starts with the geodetic coordinate system of WGS84 selected.  This will launch the Select Coordinate System dialog.

  3. To select the Mercator world projection, in the tree view on the left, go to Projected>World and select Mercator in the coordinate system list in the right hand pane.  Click OK to close the dialog.

  4. Since the coordinate systems for input and output both use the WGS84 datum, a datum transformation is not necessary.

  5. Your settings should now look like this:

  6. Click the Calculate button. This will begin the transformation process. Once the transformation process is complete, the Conversion Status pane at the bottom will say "Finished".

  1. You can then open the output file in a GIS application or within the Calculator's own viewer.