Occasionally it is useful to force the conversion of latitude and longitude to a specific UTM zone. This most commonly occurs when you have several points near a UTM zone boundary. By forcing the conversion to a specified zone you ensure that all the UTM coordinates are in the same coordinate system. For example, Dartmouth College, in Hanover, NH (Latitude: 43.702, Longitude: ‑72.29) is in UTM zone 18 while the University of New Hampshire in Durham, NH (Latitude: 43.133, Longitude: -70.926), like most of New Hampshire, is in UTM zone 19.
The optional zone parameter in the LatLongToUTM function allows you to force the conversion of a particular location (e.g. Dartmouth) into a specific UTM zone coordinate system (e.g. UTM zone 19). In the above example, select an empty cell and then choose the “LatLon To UTM” command from the GeogTools menu.
In the dialog box that appears, enter the cells containing the latitude and longitude, as requested, and enter the zone you want to force the conversion into (19) in the last box.
Click OK and GeogTools will calculate the UTM coordinates in the requested UTM zone.