Map, Compass & GPS

Map, Compass & GPS
Wild flowers along Fall Creek on the way to the Green Lakes - Oregon

Saturday, June 25, 2011

GPS Setup - Map Datum

Getting to the right destination is important to the backcountry traveler.  Setting your GPS to the right Map Datum makes a big difference.  Not selecting the right datum could put you miles away from your intended location!!!!
Datum is a term that GPS users should be aware of.  It is a set-up function and option found on all receivers.

Figure 1 The units page where you can change map datum.

In essence, map datum is a mathematical model used to take information from a spherical earth and adjust that information for placement on a flat map.  Of course we can get much more technical but in reality, that is about all the hiker/hunter needs to know.
It is the application of datum that is important to hikers.
Today, most US Geologic Survey (USGS) topographic (topo) maps are based on a map datum called the North American Datum of 1927; or NAD 27.  This information is found at the bottom left of a topo.

To read the rest of the article go here.

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