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# Introduction

This website explains how to locate a place in Tasmania using numbers.

There are two ways to do this. You can either state the latitude and longitude ('lat/lon') of the place, or you can give the grid reference of the place in the UTM system. Both methods are explained on these pages.

Here's an example, a place in the centre of Tasmania:

 Location in words summit of Gaol Hill, ca 5.5 km S of Waddamana Lat/lon 42°10'34"S 146°45'14"E Grid reference DP796306

How to get those numbers?

• GPS. If you were standing on the summit of Gaol Hill with a GPS unit in your hand, you could set the GPS to record either the lat/lon or the grid reference of your position.
• Digital map. You could determine both the lat/lon and the grid reference using the Tasmanian government's online LISTmap service, or you could get the lat/lon alone from Google Maps.
• Google Earth. You could determine the lat/lon or the grid reference using Google Earth.
• Paper map. You could find Gaol Hill on the 1:25 000 scale 'Waddamana' map sheet produced by the Tasmanian government. You could then use the grid of UTM lines on the map to estimate the grid reference of the summit. How to do this is explained on the locations from maps page. (You could estimate the lat/lon from the map as well, but that's a lot harder to do.)

This website also explains the 'fiddly bits' in locating with numbers. For example, the Gaol Hill lat/lon could be annotated as 42°10'34"S 146°45'14"E (WGS84), and the grid reference as DP796306 (GDA). The strange-looking codes in brackets (WGS84, GDA) are datums, which are discussed on the datums page.

There are several different ways to write the same lat/lon. A GPS unit, for example, might show the Gaol Hill summit as 42°10.567'S 146°45.233'E or as -42.17611 146.75389. There are also different formats for UTM grid references, and your GPS unit might report 55G 479674 5330629. The different formats are explained on the latitude/longitude and UTM grid references pages. You can convert from one lat/lon or UTM format to another using the information on those pages, or you can use your GPS or Google Earth to do the job for you.

Converting lat/lon to UTM grid reference (and vice versa) is not as simple as interconverting formats. On the conversions page is information about free software and websites that interconvert lat/lon and grid references, with some cautions about their use.

King Island is a special part of Tasmania because it straddles two different UTM grid zones. If you're reporting grid references from King Island, be sure to read the page on the King Island problem.

Two very important issues in locating a place are error and uncertainty. Is your location just where you say it is? Plus or minus how much? How do you know?

Finally, on the locations in words page you'll find a discussion of problems involved in using words to describe where a place is located. Best practice is to use both words and numbers.