The Georeferencing Calculator described in this document is a java applet created as a tool to aid in the georeferencing of descriptive localities such as those found in museum-based natural history collections. It was specifically designed for the Mammal Networked Information System (MaNIS) Project and has been adopted as well by HerpNet and ORNIS. The application makes calculations using the methods described in the Georeferencing Guidelines.

It will be useful to run the calculator while reviewing this document; to do so, click here. When the application is finished loading it should look something like Figure 1, below. Click on the button on the right side of the Calculation Type drop-down list box to expand the list.

When the list is expanded, the application should appear as in Figure 2, below. Select the calculation type you want to perform. If you want to figure out coordinates and errors based on a named place and offsets, select the "Coordinates" option. If you already have the coordinates for the complete locality description and you only want to calculate the error, select the "Error" option.
NOTE: Selecting the "Error" option will always give decimal latitude and longitude equivalent to the coordinates entered while the "Coordinates and Errors" option will give always decimal latitude and longitude different from those entered if there is one or more offsets in the locality description.

Go directly to the section on Calculating Errors only

Calculating Coordinates and Errors
After selecting the Coordinate calculation type, a new drop-down list box for Locality Type will appear on the screen. When this list is expanded, the application should appear as in Figure 3, below. Select the locality type that best matches the locality for which you are trying to determine the maximum error distance.
NOTE: The calculator is only capable of calculating coordinates for the locality types listed. Coordinates for other types of localities should be determined by traditional means.

After selecting the locality type, a number of controls will appear on the page. These controls allow you to enter or choose values for all of the parameters relevant to the selected locality type. Figure 4, below, shows an image of the Georeferencing Error Calculator when a locality type of "Distance at a heading" is selected from the Locality Type drop-down list.

Suppose the locality you are trying to georeference is "10 mi E (by air) Bakersfield" just as in the example for the "Distance at a heading" locality type. Suppose also that you've obtained the coordinates for Bakersfield (35° 22' 24" N, 119° 1' 4" W) by interpolating the center of town to the nearest second from the USGS Gosford 1:24,000 Quad map.

Select the degrees minutes seconds option from the Coordinate System drop-down list, then enter the coordinates for Bakersfield in the Latitude and Longitude controls that appear.

Select "USGS map: 1:24,000" from the Coordinate Source drop-down list.

The Gosford Quad map uses the North American 1927 horizontal datum (you can find that printed on the bottom of the map), so select "(NAD27) North American 1927" from the Datum drop-down list.

You've interpolated the coordinates to the nearest second, so select "nearest second" from the Coordinate Precision drop-down list.

In this example, the offset distance is 10 mi, so type "10" in the Offset Distance text box and make sure that "mi" is selected in the Distance Units drop-down list.

Bakersfield is quite a big place and we don't know if the original locality meant 10 miles from the center of town or 10 miles from the city limits (or something else entirely), so, given that it is 3 mi from the interpolated coordinates to the east edge of town, the Extent of Named Place should be 3 mi. Enter "3" in the Extent of Named Place text box.
NOTE: If you had measured this distance in kilometers you'd have to convert it to miles and enter that number because the calculator requires that all distance measurements be in the same system.

The distance component in this locality is 10 mi, which is precise to the nearest mile (see the discussion on this topic in the Georeferencing Guidelines). Select "1 mi" in the Distance Precision drop-down list.

The directional component of the locality is east. Select "E" in the Direction Precision drop-down list.

Now that all of the parameters for this locality have been entered, click on the Calculate button. The calculated coordinates (in decimal degrees) for the locality ("10 mi E (by air) Bakersfield" in this example), and the maximum error distance for the calculation will be given in the controls at the lower left of the page as shown in Figure 5, below.

The results, in blue, can be highlighted and copied onto the system clipboard using standard copy and paste key combinations. The long text box at the bottom of the page contains a tab-delimited record of the data for the current calculation. These data can be copied all at once and pasted into an Excel spreadsheet or into a record in Access that has the same field order. The data are given in the following field order:

Original Coordinate System, Coordinate Precision, Distance Precision, Decimal Latitude, Decimal Longitude, Datum, Maximum Error Distance, Distance Units, Extent of Named Place
NOTE: Whenever you make a new selection on the Coordinate System drop-down list, the Coordinate Precision will reset to "nearest degree." Be sure to set the Coordinate Precision after changing the coordinate system.

To begin a new calculation, select the locality type from the Locality Type drop-down list and enter all of the parameters for the new locality in the controls below the drop-down list. If the locality type is the same as for the previously georeferenced locality it is not necessary to select the locality type again. Values selected in the drop-down lists will remain selected until changed by the user, thus facilitating calculations for groups of localities having the same named place.

Calculating Errors only
After selecting the Error calculation type, a new drop-down list box for Locality Type will appear on the screen. When this list is expanded, the application should appear as in Figure 6, below. Select the locality type that best matches the locality for which you are trying to determine the maximum error distance. The calculator is able to calculate the maximum error distance for all of the types of localities described in the Georeferencing Guidelines.

After selecting the locality type, a number of controls will appear on the page. These controls allow you to enter or choose values for all of the parameters relevant to the selected locality type. Figure 7, below, shows an image of the Georeferencing Calculator after a locality type of "Distance at a heading" was selected from the Locality Type drop-down list and the same parameters were entered as for the example in the Calculating Coordinates and Errors section, above.

The results, in blue, can be highlighted and copied onto the system clipboard using standard copy and paste key combinations. Only those controls showing on the page when the Calculate Error button is clicked will figure into the error calculations.
NOTE: Whenever you make a new selection on the Coordinate System drop-down list, the Coordinate Precision will reset to "nearest degree." Be sure to set the Coordinate Precision after changing the coordinate system.

To begin a new calculation, select the locality type from the Locality Type drop-down list and enter all of the parameters for the new locality in the controls below the drop-down list. If the locality type is the same as for the previously georeferenced locality it is not necessary to select the locality type again. Values selected in the drop-down lists will remain selected until changed by the user, thus facilitating error calculations for groups of localities having the same named place.

System Requirements:
The application has been tested on a number of different configurations. Expect it to work in Netscape, Internet Explorer, and Mozilla on any operating sytem in versions that accomodate Java 2.

I haven’t tested the memory requirements of this application. Expect a minor delay the first time you load the calculator into your browser. After that, the files will be cached if your browser settings allow this, and the loading will be much faster.