The Advantages of Using Precise Co-ordinates

Even if your latitude and longitude co-ordinates are definitely correct, if you use data that is precise only to the nearest minute of arc (e.g. 52n36), you can still only achieve an accuracy of about a mile (1.6 km) radius with this.

Therefore we recommend always using degrees, minutes and seconds of arc (e.g. 52n36’28) wherever possible.
This will give precision to within about 30 metres on the ground (providing the co-ordinates are accurate as well as precise, of course!). See also The Problem of Zero Longitude

Where our co-ordinates originate from the GNIS Server and only give the nearest minute of arc, you can use the map provided to improve the accuracy (though for some countries the maps are not yet detailed enough to do this outside large cities).


In an astrological chart, even just a mile or two out can make a slight difference to the natal angles, some transits and some progressions. Fifty miles out (yes, we have discovered errors of that magnitude when testing some well-known co-ordinate collections provided to astrologers) is easily enough to tip a cuspal birth-chart into a different Rising-Sign, for example.