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| METHODS OF EXPRESSING SCALE
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| The scale of a British map is expressed as either a "scale in words" or
as a "representative fraction (RF)'. Both methods are normally shown on
each map and on sheet 99 of series M726 edition 6-GSGS you can see on the
front that the scale is expressed as both "1 ¼ inches to 1 mile" (The scale
in words) and as"1:50,000" (The RF). The words explain the distance on the
map that represents a certain distance an the ground, whereas the fraction
expresses the distance on the map as a fraction of the corresponding distance
on the ground. |
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| Example 1 |
| To discover the length of 1 mile on a 1:50,000 map: - On a 1:50000 map,
all distances are 1/50000 x the distance on the ground. - As there are 63,360
inches to a mile, one mile therefore equals 63360/50000- 1.27 inches. |
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| THE SCALE LINE
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| The scale line is drawn to assist in the measurement of distances, and
shows how distances are represented on the map. |
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| Look at the scale on the bottom of MS 99 and it can be seen that the distances
are shown in kilometres, statute miles and nautical miles. (On some maps
they may even be sub-divided into yards, metres or feet - but don't confuse
this with the conversion table, to the left of the scale, which is NOT drawn
to scale.) |
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| Note that the scale does not start at '0'. To the right of '0' there are
a number of large divisions, each division representing the unit of scale
mentioned. To the left of '0', one of these divisions is sub-divided to
show simple fractions of the main unit numbered from right to left. If you
take the top scale (in kilometres) it can be seen that each sub-division
represents 100 metres. |
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| On the 1:50,000 scale map an easy unit of measurement is to use the grid
square: each square is 1000 metres x 1000 metres. |
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| You should try to measure distances on the map and convert them to real
distances. Use a piece of paper to do this. Lay it on the map so that the
edge goes through the two points that you want to know the distance between.
Mark the paper with two marks (on the edge) that coincide with the two positions.
Move the paper to the scale at the bottom of the map placing one point at
the zero position and read off the distance where the other point is on
the scale. |