Geographic Calculator Overivew

The Calculator is used in several different ways.

1. Calculating Declination. Magnetic Declination is the difference between true north and magnetic north. Since cavers usually survey with magnetic compasses, declination effects the accuracy of cave surveys. This especially true for caves that are surveyed over a long period of time since declination changes over time. This can cause severe loop closure errors between survey that were done at different times.

As a result of this problem, the Geographic Calculator allows you to calculate the magnetic declination for a particular location and date. Because of the fact that the declination is calculated for a precise time and date, it can be much more accurate that the usual methods such as reading it off a map.

2. Doing Calculations. The Geographic Editor/Calculator is divided into two main sections. The top half handles Longitude and Latitude and the bottom half handles UTM. If you are working with Longitude and Latitude, you simply enter or read values in the boxes at the top. If you are working with UTM, you enter or read values from the bottom.

3. Converting Between Different Units. The Calculator also allows you to convert between Longitude and Latitude and UTM and vice versa. The process is extremely easy. As you enter a location in either Longitude/Latitude or UTM, the program automatically converts it to the other value.  This makes it easy to convert from one unit to another.

4. Calculating UTM Convergence Angles. You can also use the Geographic Calculator to calculate the UTM Convergence angle. This angle is used to rotate the cave to match the local UTM grid. Once you have made entered the cave’s location, the convergence will be automatically calculated and appear in the lower right part of the window.

5. Converting Between Different Datum. It is sometimes useful to convert Longitude and Latitude measurements from one datum to another. To do this, first make sure the “Enable Datum Conversion” checkbox is enabled.  Next, simply select a different datum. The program will automatically convert the coordinates to the new datum. Click here for more information about converting between different Datum.