There are so many different map co-ordinate systems; Just looking at my Sat-Nav gives me a choice of about 30 different Position Formats, everything from DD MM SS.S to Borneo RSD, Irish ITM, and many others.
The DD MM SS.S is the preferred Aeronautical method, but beware of the similar DD MM.MMM system used by some.
If you want to take height into account, then there are also several approximations. WGS84 is a popular Mapping Spheroid.