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On walks we often say something like
“We’ll meet you on the river flat at 5pm”. While this usually works out,
it is open to misinterpretation - eg "where on the river flat?",
or even "which river?" Many years ago I was a member of a group
waiting at upper Jamieson Hut, while another group was looking for us
at Fry’s hut. When the question was asked “where will we meet” the answer
was “down by the creek where we camped two years ago”. While everyone
concerned knew exactly what was meant, it could be ambiguous to a group
that didn’t know the area. Grid references are a very easy, very accurate
and (almost) foolproof method of pin-pointing a position. We use them
when quoting a location in the Melways. (For example the MCG is on map
2G at point D6). It is just as easy in the bush.
Every walking map you use will be
divided into 1Km squares. If you look at the margins of a map you’ll see
that they’re numbered. Our map shows the numbers 66 & 67 on the East West
(horizontal) axis and the numbers 48 & 49 on the North South (vertical)
axis.
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then be used to quote a grid reference for a 1Km x 1Km square. To
quote the position of a 1km square just remember that you have to
go across before you go up. With this imprinted on your brain you
will be able to quote the grid reference of the square, which in this
case is 66 48.To make things even simpler, all walking maps use the
same grids, so a grid reference taken from one map will identify the
same location on another map of the area produced by a different organisation
or on a different scale. |
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Because this “four figure grid
reference” only gives the location within a 1km square and we usually
need something more accurate than this, most people use a “six figure
grid reference” which places the location within a 100m square.
To do this imagine that every 1km grid square is further divided
by an extra 10 vertical lines and 10 horizontal lines. Imagine that
these lines are numbered 1 to 10. For example the North South grid
lines shown on the our map will now read 660, 661, 662 --- 669,
670. With these extra imaginary lines you can identify the position
X as shown on the map as 662 484. Remember that the whole of the
box that contains the X is will be grid ref 662 484. In this way
you will always be able to accurately identify any location on a
map.
One final point; If you look
closely at a real map, you will notice that the 1km grid values
listed along the edge (ie 66 and 48 in the example) are preceded
by another value in smaller print (eg 5948).
The smaller figure refers to a larger grid of 100 x 100km squares.
Normally this is ignored, as provided you specify which map you
are using, a six figure grid reference will still be unambiguous.
Even the smallest scale topographic maps you are likely to walk
with (1:100,000) won't exceed an area 100 x 100km. These figures
are included in a GPS reading however, specifying a unique location
within Australia.
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