There are two coordinate systems in use that a hiker should know. UTM (Univeral Transverse Mercator) is used on maps such as the USGS and Green Trails. Latitude and longitude is the other coordinate system and has 2 forms. Degrees Minutes Seconds is the original form used by sailers. This has been modified to a Decimal Degrees notation that is used by websites and GPS systems. A thorough understanding of these systems may not be necessary. Just understand that each can uniquely identify a location. Given this you can find a location on a paper map, enter it into a GPS, computer or website to get information about a location and even call in a rescue should someone get hurt in the mountains.
The important thing is to be able to recognize the different formats of coordinates. The following are the coordinates for the beginning and end of the Annette lake trail in all three formats. Get familiar with these so that you know what you are looking at when you find them on websites and maps etc.
Annette Lake TrailheadDecimal Degrees latitude and longitude
47.3929, -121.4738
Degrees Minutes Seconds latitude and longitude
47°23'34", -121°28'26"
Univeral Transverse Mercator
10T 0615174E 5249952N
Annette Lake Trail End
Decimal Degrees latitude and longitude
47.3603, -121.4749
Degrees Minutes Seconds latitude and longitude
47°21'37", -121°28'29"
Univeral Transverse Mercator
10T 0615167E 5246334N
Next in this tutorial is Finding Coordinates