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Locations from maps

Tasmanian paper maps are overlaid with a grid of lines based on the UTM system. You can locate any place in Tasmania by estimating its grid reference in this system from the map. For an example, see the map image below (at left), taken from the 1:25 000 scale Mole Creek mapsheet (image supplied by TASMAP, State of Tasmania; grid is based on AGD66 datum). We'll estimate a grid reference for the creek junction marked with a black arrow.


1:25K base
 

Before we go any further, please note that Tasmanian 1:25000 scale maps are also available online through the LISTmap service. As explained on the LISTmap page, it is much easier to get a UTM grid reference (or a lat/lon) for a mapped location using LISTmap than it is to follow the procedure described below. What follows are instructions for getting a grid reference from a 1:25000 scale paper map.

The gridlines on the map mark off 1 km squares. The square shown is bounded on the west by the line labeled 47, on the east by the 48 line, on the south by the 98 line and on the north by the 99 line. The meaning of those numbers is explained on the UTM grid references page. On a real map the line numbers are printed along the map's border. They've been pasted on the map image here for convenience.


East-west distances are called eastings. Within our 1 km square, the easting of the creek junction is some portion of the 1 km distance between grid lines 47 and 48. Estimate this portion by dividing the 1 km east-west distance into ten 100 m sections. You can do this by eye, or by measurement with a ruler (each 4 mm on the 1:25 000 map is 100 m on the ground) or by laying a transparent scale rule on top of the 1 km grid square, as shown on the left. The easting for the creek junction is 476, meaning the junction is approximately 600 m east of the '47' 1 km line.

easting
 

North-south distances are called northings. Estimate the northing of the creek junction as you did for the easting, and you'll see (at right) that the northing is 986. In other words, the junction is approximately 600 m north of the '98' 1 km line. You might want to judge that a bit finer and call it 650 m, but as discussed on the error page, it's best to estimate to the nearest 100 m.

northing
 

The grid reference so far is 476 986. The last step is to find the 2-letter code for the 100 km grid square in which our creek junction is located. A 2-letter code is given in the legend of the map, and for the Mole Creek mapsheet is DP. The grid reference for the creek junction is written DP476986.

If you forget how to estimate and write grid references, don't despair! The instructions are given in the map legend. The image at left shows the instructions on the Mole Creek mapsheet.

instructions

DP476986 is in 2-letter, 6-digit format. This UTM format and others are discussed on the UTM grid references page. The datum is AGD66 (see datums page).