The latitude/longitude system

Longitude lines (example in blue at right) run north-south and meet at the North and South Poles; they are also called meridians. Latitude lines (example in red at right) run east-west and don't meet. For this reason they are also called parallels. Longitude divides the Earth's surface into 360 thin slivers of one degree each. Latitude divides the Earth's surface into 180 thin rings of one degree each. These divisions and their numbering are easier to see if you map the Earth as a flat sheet instead of a sphere. In the sphere to the right and in the flat map below, the lat/long gridlines are drawn five degrees apart.

The 360 one-degree longitude lines are numbered in two 180-degree lots running east and west from the 0º line of longitude (also called the prime meridian). The 0º line runs through Greenwich, England. Halfway around the globe is the longitude line (in the mid-Pacific) which is both 180º east and 180º west of Greenwich. The main island of Tasmania lies between 143ºE and 149ºE longitude.

The 180 one-degree latitude lines are numbered in two 90-degree lots running north and south from the 0º line of latitude, which is the Equator. The North Pole is 90ºN and the South Pole is 90ºS. The main island of Tasmania lies between 40ºS and 44ºS latitude.

Each degree of latitude and longitude is divided into 60 minutes, and each minute is divided into 60 seconds. Both latitude and longitude are usually written as degrees (symbolised º ), minutes ( ' ) and seconds ( " ). In the lat/long system, a location is specified by giving its latitude first, then its longitude. For example, the Queen Victoria Museum at Royal Park in Launceston is at 41º26'23"S 147º07'58"E (AGD66).

It's important to remember that even though the lat/long grid on the flat map looks like a grid of squares, it isn't that way on the real Earth (see the sphere above). The distance between one-degree lines depends on where you are. It's largest at the Equator and smallest at the Poles.

Lat/long formats

41º 26' 23"S is in degree-minute-second format, abbreviated DMS. Three other formats are in common use for lat/long:

Decimal degrees, or DD. This format gives degrees latitude (or longitude) as a simple decimal. For example, 42.5000°S is 42 and a half degrees, which is the same as 42° 30' 00"S. Decimal degrees are also symbolised as DDD.dddd.

Decimal minutes, or DDDMM.mm. This format gives whole degrees and decimal minutes. For example, 42° 24.33'S is 42 degrees, 24 and one-third minutes, which is the same as 42° 24' 20"S.

Decimal seconds, or DDDMMSS.s. This format gives whole degrees, whole minutes and decimal seconds. For example, 42° 15' 31.7"S is 42 degrees, 15 minutes and 31 and seven-tenths seconds. In DMS format this would be rounded up to 42° 15' 32"S.

You can convert between lat/long formats using the tools on the conversions page. If you prefer to do your own conversions, see the formulas below:

   DDD° MM' SS" (DMS)
   = (DDD + MM/60 + SS/3600)° (decimal degrees)
   = DDD° (MM + SS/60)' (decimal minutes)

   DDD.dddd° (decimal degrees)
   = DDD° (60 x 0.dddd)' (decimal minutes)

   DDD° MM.mm' (decimal minutes)
   = DDD° MM' (60 x 0.mm)" (decimal seconds; round off for DMS)

top of page