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THE ONLY WAY IS UP!
Area and Grid References
Topographical maps are very useful for showing the LOCATION of features. Numbered grid lines drawn on the map persmits the pinpointing of features, and expressing their locations by using the numbers. The grid lines are made up of:
EASTINGS - vertical lines numbered from west to east (left to right)
NORTHINGS - Horizontal lines numbered from south to north (bottom to top)
The numbers which refer to the Eastings and Northings of a grid on a topographic map are local numbers and are not related to degrees of longitude and latitude.
An area reference is a way of referring to a particular grid box. Of course, any grid box has four corners – so which do we use as the unique area reference for a particular grid box? The answer is that we all agree to use the bottom left hand corner as the eastings and northings that identify a particular grid reference. So, the area reference has four numbers, being two digits for the easting, and two digits for the northing at the bottom left hand corner of the grid square.
An easy way to remember that area references have four digits, and grid references have six digits, is that the A in Area comes before the G in Grid and therefore has less digits in the reference.
A grid reference is much more precice than an area reference as it is more specific, it has more numbers – it uses six numbers by comparison to the four numbers used for the area reference. The extra detail is created by dividing the vertical and horizontal edges of the grid square into tens – imagining that there are ten vertical lines within the grid square, and ten horizontal lines within the grid square. The first two digits is the easting, and the third digit is a number between 0 and 9 which indicates at what tenth along the point is. Similarly, the fourth and fifth digits are the northing, with the sixth digit identifying at what tenth along the northing the point is located.
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