Geographic Coordinates

Geographic coordinates (latitude and longitude) are displayed in several formats.

Most of the passes and gaps shown on this web site are documented by the United States Board on Geographic Names
which displays the latitude and longitude in the format dddmmss-direction.
This example from the Berthoud Pass page (which was copied from the USGS site) shows the pass is located
at 39 degrees, 47 minutes and 54 seconds North, and 105 degrees, 46 minutes and 40 seconds West.

Feature Name ID Class County State Latitude Longitude Ele(ft) Map BGN Date Entry Date
Berthoud Pass 181335 Gap Clear Creek CO 394754N 1054640W 11325 Berthoud Pass - 13-OCT-1978

The Colorado Mountain Passes Excel spreadsheet displays the coordinates in the dddmmss-direction format just as done by the USGS,
but also includes the symbols for degrees (°), minutes (") and seconds ("). For example:

Latitude Longitude
39°47'54"N 105°46'40"W

Other common formats include:
Decimal degrees - ddd.dddddd - 39.798333N 105.777778W (commonly used on Google Maps)
Degrees and decimal minutes - ddd mm.mmmmmm - 39 47.9N 105 46.666666W
Decimal degrees, decimal minutes, and decimal seconds - dd mm ss.ssssss - 39 47 54.1N 105 46 40.7W

Many GPS units can be set to accept and display the user's preferred format.
Note, north is positive latitude, south is negative latitude. East is positive longitude, west is negative longitude.
1 degree = 60 minutes. 1 minute = 60 seconds.

"The Passes of Colorado, An Encyclopedia of Watershed Divides", by Ed Helmuth & Gloria Helmuth, shows location, not with geographic coordinates, but with township and range nomenclature, such as "T7S R77W, Map 6".
"Colorado Road & Recreation Atlas" by Benchmark Maps, shows the geographic location on the vertical and horizontal borders of the maps in ddd°mm' format. Seconds can be extrapolated. For instance, the point 1/2 way between the 39°40' line and the 39°50' line would be 39°40'30" .
   Google Maps and Google Earth use formats decimal degrees (ddd.dddddd-direction), degrees and decimal minutes (ddd mm.mmmmmm-direction), and decimal degrees, decimal minutes, and decimal seconds (dd mm ss.ssssss direction - note the included blanks).
A helpful feature of Google Maps is to right click on a location, then click on "What's here?". A pop-up will appear that shows the location in the dd.dddddd, +/-ddd.dddddd format.

For more details, check these links:
Wikipedia, Geographic Coordinate System
Wikipedia, Geographic Coordinate Conversion
GIS Geography, Latitude, Longitude and Coordinate System Grids
Township and Range explanation
Township and Range - Public Land Survey System on Google Earth.

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© 2017 Randy Bishop
Last modified: August 11, 2017