GPS Setup – Using the Right Coordinates – Part 2

By Blake Miller

I have received a few emails about what coordinate system to use with a GPS?

Coordinate system refers to the geographic grid used on a map; Latitude and Longitude is a coordinate system.  The GPS receiver may call it position format.

My recommendation would be to consider:

1.    When traveling outside of the United States find out what system the visited country uses.  The GPS receiver has coordinate systems pre-loaded for many countries around the world.

 

a.    On a Garmin select “Setup” then select “Units” (below).

 

 

b.    Select the drop down menu under “Position Format” and rocker down to view the country options.

c.    If on a tour or with a guide ask which coordinate system they use.

 

2.    In the United States, take a look at the map to be used for the trip during pre-trip planning.  Some of the options will be:

a.    Latitude and Longitude in various formats:

                                          i.    Degrees Minutes Seconds

                                        ii.    Degrees Minutes.minutes

                                       iii.    Degrees.degrees (this is rare)

b.    Universal Transverse Mercator Grid.

c.    The Public Land Survey System (PLSS) – Township Range & Section.  This coordinate system is found on National Forest maps.  This system will not be an option in the GPS receiver.  PLSS has been around for around 200 years.  The Forest Service and industry still uses it.  It’s a bit tedious to use.  A good reference for the PLSS is to visit:

http://nationalatlas.gov/articles/boundaries/a_plss.html

 

For more information about selecting the right coordinates using Latitude and Longitude visit: http://outdoorquest.biz/gps_setup__using_the_right_coor.htm

 

I’d also suggest consider using Universal Transverse Mercator (UTM – listed above).  UTM is a grid system that is simple and easy to use; young people can grasp this grid concept easily. The system was inspired by the military and developed in the 1940’s.  This grid is a basic X/Y grid; up & down, left & right. 

 

Text Box: The spacing between “ticks” is 100 meters

 

Text Box: Spacing between coordinates is 1000 meters

 

 

 

The map above is a USGS topographic map (scale is 1:24,000) with a UTM grid overlaid on the map.  The grid squares are 1000 meters by 1000 meters.  Terrain Navigator map software provides an outstanding border that identifies the coordinate data.  Between each coordinate are small tick marks that have a spacing of 100 meters.

 

Dick Blust Jr.’s article captures the essence of UTM:

 

“OK, here's how it works in a nutshell: a UTM coordinate is your distance from west to east across your zone in meters - your Easting - and, again in meters, your distance north of the Equator - your Northing. That's it. Period. The key thing to remember about UTM is that it only deals with two directions: west moving east and south moving north: the numbers always get bigger as you go east, and they always get bigger as you go north. Always. Everything, therefore, is east and north, or, if you prefer, right and up. The way UTM breaks down, every square meter has - indeed, is - its own coordinate.”

 

Read more of Dick Blust’s articles at: http://www.kifaru.net/navigate1.htm

 

A fine reference for learn UTM grid is Lawrence Latham’s book “GPS Made Easy.”  Chapter 5 has an easy to understand tutorial on this grid system; that’s how I learned it.

 

Of course there is a bunch of information on the internet.

 

Because I use my Terrain Navigator (USGS maps) software a lot in my land navigation classes, hiking and hunting I find myself using UTM almost exclusively.  A basic HP/Epson printer provides a map of excellent quality, clarity and detail.  For my trips I will print my maps at the standard scale (1:24,000) of my route; this may require the printing of several maps.  I will also print a map zoomed out one level that provide a readable scale at about 1:48,000; this gives the broad overview of the route.  The new map set is stored in a 1 gallon ziplock bag in my pack.  I provide a set to my hiking partner and one stays home with my trip plan (visit my web side to download the trip plan at: http://outdoorquest.biz/Links.htm.)  Maps are printed on 8 ˝ x 11 paper.