(to Western Hemisphere,Eastern Hemisphere,Footprints by Dish Size)
Latitude/Longitude Convention
and Degrees to Decimal Conversion
(dish size list)

Footprints by Dish Size - Magnetic Deviation - Latitude/Longitude Convention - Explanation Chart
Latitude is measured from the equator, with positive values going north and negative values going south. Longitude is measured from the Prime Meridian, the longitude that runs through Greenwich, England), with positive values going east and negative values going west. So, for example, 65 degrees west longitude, 45 degrees north latitude is -65 degrees longitude and +45 degrees latitude. 

To convert your site's coordinates from degrees, minutes, seconds format to decimal format, use this easy
degrees + (minutes/60) + (seconds/3600).

For example: Site coordinates of

42º 8' 10"

would be calculated as:

42 + (8/60) + (10/3600) = 42.1361
42 + (.1333) + (.0028) = 42.1361.

NOTE: You can round to any decimal place, but is suggested to go to the 4th decimal place.