Calculating Global Coordinates

Latitude and longitude can be used to give accurate descriptions of any point on the surface of the globe. These global coordinates are measured in degrees, minutes and seconds. There are 60 minutes to a degree, and 60 seconds to a minute, so they are cumbersome units to work with.

To simplify the units, sometimes positions are expressed in fractions of a degree, for example the latitude of Hornsby Railway Station in Sydney, is approximately 33.705 deg S (the longitude is approximately 151.097 deg E). Unfortunately there is no standard for expressing global coordinates, so map users must often convert from one to the other.

Example:

Express the location of Hornsby Station in degrees, minutes and seconds.
33.705 degrees
= 33 degrees .705 x 60 minutes
= 33 degrees 42.3 minutes
= 33 degrees 42 minutes .3 x 60 seconds
= 33 degrees 42 minutes 18 seconds
or using symbols
= 33ø 42' 36" S

Quiz:

Give the longitude of Hornsby Station in degrees, minutes, seconds.

By dividing by 60, locations expressed as degrees, minutes, seconds can be easily converted back to fractional degrees.
Click here to see more examples.

However latitudes and longitudes are not useful for a number of other tasks, in particular they cannot readily be used to estimate the distance between 2 locations, as longitude varies depending on what latitude it is measured at. One degree of longitude is 111km at the equator, but zero distance at the poles.

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