Basic Operation

To convert a set of coordinates from one coordinate system or map projection to another, and/or transform it from one datum to another, follow these steps:

1. If the desired input coordinate reference frame type is not already displayed in the upper half of the window, select the desired entry from the pull-down list. The upper half of the window will be updated to display the appropriate parameter and coordinate fields for the selected input coordinate reference frame type.

2. If the desired input datum is not already displayed in the upper half of the window, select the desired datum using the Datum pull-down list. (In the Windows version, click on the arrow to open the list, use the scroll bars if necessary to bring the desired entry into view, then select it by clicking on it. In the Motif version, click on the arrow button to open the list, use the scroll bar if necessary to bring the desired entry into view, then select it by double clicking.) The datum list contains global datums (WGS-84 and WGS-72) first, followed by seven-parameter local datums, and then by local 3-parameter datums, with each section in alphabetical order. When you select a datum, the Ellipsoid field is updated to show the code and name of the ellipsoid associated with the selected datum. (Note: you cannot select a specific ellipsoid directly.)

3. If the input coordinate reference frame has any parameters associated with it (e.g., a central meridian), and the default parameter values displayed in the upper half of the window are not the desired values, change the parameter values by selecting the displayed values and typing over them.

4. Enter the input coordinates in the fields displayed in the upper half of the window by selecting each field and typing over its contents. Optionally, specify the accuracy of the input coordinates by entering values, in meters, in the 90%CE, 90%LE, and 90%SE fields, or by selecting an entry from the Sources pulldown menu.

5. If the desired output coordinate reference frame type is not already displayed in the lower half of the window, select the desired entry from the pull-down. The lower half of the window will be updated to display the appropriate parameter and coordinate fields for the selected output coordinate reference frame type.

6. If the desired output datum is not already displayed in the lower half of the window, select the desired datum using the Datum pull-down list, just as for the input datum.

7. If the output coordinate reference frame has any parameters associated with it (e.g., a central meridian), and the default parameter values displayed in the lower half of the window are not the desired values, change the parameter values by selecting the displayed values and typing over them.

8. Click on the Convert: Upper-to-Lower button. The output coordinates will be displayed in the coordinate fields in the lower half of the window. The 90% circular, linear, and spherical error values will also be updated.