When used properly, this spreadsheet will correctly figure coordinates and locations from a 7.5 minute, USGS topo map. It will also convert measured distance, on the map, to real distance and vice versa. This spreadsheet should be used only with a 7.5 minute USGS topo map.
On the first section of the sheet, "Finding a coordinate from a location," you enter your measurement, in inches, and the values of the coordinate line you measured from, into the appropriate blue cells of the sheet. When you do this and hit "Enter" the new coordinate will show in the green cell, to the right of the original coordinate and on the same line. Since the coordinate lines on the map are listed only in Degrees, Minutes and Seconds, that's the way you enter your original coordinate into the blue cells. However, since some GPS units give readings in Degrees, Minutes, Seconds and Thousandths of a minute, that's how the coordinates are shown in the green area, where your new, figured coordinate, will appear.
In the next section of the sheet, "Finding a location from a coordinate," in the box labeled "Original coordinate," simply enter the values of your original coordinate into the appropriate, blue cells. In the column labeled "Thou Min / Secs," you can enter that part of the coordinate in seconds, or thousandths of a minute. Either will work, just fine. Next, in the box labeled "Coordinate line closest to original coordinate value," you look on the map and find the coordinate line that's closest to the values of your original coordinate and enter the values of that coordinate line into the appropriate blue cells of that box. When you've done this and hit "Enter," the box labeled "Location, figured from the original coordinate" will show how far you need to measure from the appropriate coordinate lines, to get your new location.
The box labeled "Orig. Thou. Min. to Secs. and Vice Versa" in the "Finding a location from a coordinate" section is for reference only. If you enter the value of your original coordinate in seconds, this box will convert it to thousandths of a minute, or if you enter the value as thousandths of a minute, it will convert it to seconds.
In the box labeled "Converting measured distance to real distance," you simply put the distance, measured on the map, into the blue cell of the box and hit "Enter." Once you do this, in the green cells, the sheet will display the real distance in miles, meters, yards and feet, for the measured distance.
In the box labeled "Converting real distance to measured distance," in the blue cells, you enter the number of miles, meters, yards or feet that you want converted to measured distance and hit "Enter." Then, in the green cells, the sheet will display the measured distance, on the map, for that real distance.
To the best of my knowledge, this spreadsheet will accurately figure locations, coordinates and distance, both measured and real, from
any 7.5 Minute USGS topographical map. However, it is each individual's responsibility to verify, through every reliable means available, that all
calculations regarding navigation are correct and applicable to any planned excursion. Should anyone find a problem with
this spreadsheet, please let me know.
