GPS coordinate formats explained
The three common ways to write latitude and longitude, where each is used and how to read them.
Decimal degrees (DD)
Decimal degrees write the whole coordinate as a single signed number, such as 40.7128, -74.006. Positive latitude is North, negative is South; positive longitude is East, negative is West. This format is the easiest to store, sort and use in code, which is why mapping APIs and spreadsheets prefer it.
Degrees minutes seconds (DMS)
DMS splits each coordinate into whole degrees, minutes and seconds, like 40 42 46 N. There are 60 minutes in a degree and 60 seconds in a minute. DMS is the traditional notation on paper maps and nautical charts and is still common in surveying.
Degrees decimal minutes (DDM)
DDM keeps the degrees and minutes but writes the seconds as a decimal fraction of a minute, like 40 42.768 N. Most handheld and marine GPS units default to this format because it balances precision with a compact display.
Converting between them
To go from DMS to decimal, add the minutes divided by 60 and the seconds divided by 3600 to the degrees. To go the other way, take the fractional part of the decimal degrees, multiply by 60 for minutes, then take the new fractional part and multiply by 60 again for seconds.