Reading and writing coordinates
Degrees, minutes, seconds and signs
Teaching this? Open projector mode
A place has two coordinates, and both can be written in two common styles.
In decimal degrees each number is a single decimal, such as 48.86. In degrees, minutes and seconds (DMS) a degree is split like an hour: 1° = 60 minutes (′) and 1′ = 60 seconds (″). To convert DMS to decimal, use
decimal = degrees + minutes/60 + seconds/3600
For example 40° 30′ is 40 + 30/60 = 40.5°.
Decimal coordinates use signs instead of letters. North and East are positive; South and West are negative. Sydney is at about 33.87° S, 151.21° E, which is written (−33.87, 151.21). Buenos Aires, at about 34.6° S, 58.4° W, is (−34.6, −58.4).
The ranges give you a built-in checker. Latitude must be between −90 and 90. Longitude must be between −180 and 180. A “latitude” of 151.2 cannot be right, so that number has to be the longitude.
Convert 40° 30′ to decimal degrees.
A town is at 34° S, 58° W. Which pair is correct in decimal degrees (latitude, longitude)?
A file has the point (151.2, −33.9). Which number must be the longitude?