Coordinates & places · 4 min
Read and plot coordinates
What latitude and longitude mean, the formats you will meet, and how to drop any pair on a map.
Coordinates & places
Every place has two numbers
A coordinate is a place written as two numbers. Latitude says how far north or south of the equator it is, from -90 at the South Pole to 90 at the North Pole.
Longitude says how far east or west it is of the line through Greenwich, London, from -180 to 180. Together they point at one spot on Earth.
Dublin's Spire: 53.3498, -6.2603. North of the equator (positive), west of Greenwich (negative).
Lesson notes
Everything from the cards above, on one page to come back to.
Every place has two numbers
A coordinate is a place written as two numbers. Latitude says how far north or south of the equator it is, from -90 at the South Pole to 90 at the North Pole.
Longitude says how far east or west it is of the line through Greenwich, London, from -180 to 180. Together they point at one spot on Earth.
Dublin's Spire: 53.3498, -6.2603. North of the equator (positive), west of Greenwich (negative).
Latitude first, almost always
Google Maps, phones and most spreadsheets write latitude first, then longitude, separated by a comma: 48.8584, 2.2945.
One degree of latitude is about 111 km (69 miles). So the fourth decimal place is roughly 11 metres, enough to pick out a single building.
The same place, written another way
Older maps, GPS units and legal documents use degrees, minutes and seconds (DMS). A degree has 60 minutes and a minute has 60 seconds, like a clock.
To turn DMS into decimal degrees: degrees + minutes ÷ 60 + seconds ÷ 3600. A letter (N, S, E, W) gives the sign: S and W are negative.
53° 20' 59" N = 53 + 20/60 + 59/3600 = 53.3497
Questions
Which comes first, latitude or longitude?
Latitude, in almost everything people copy and paste: Google Maps, phones and spreadsheets all write latitude, then longitude. The big exception is GeoJSON files, which store longitude first.
How many decimal places do I need?
Four decimal places is about 11 metres, enough for a building. Five is about a metre. More than six adds nothing a phone or map can use.
How do I convert degrees, minutes and seconds to decimal?
Add the degrees, the minutes divided by 60 and the seconds divided by 3600. Make the result negative for S or W.