Fig 4.1 illustrates a part of a typical grid system with the given eastings of 72 to 76 units and northing of 31 to 34 units. A and B are two points on the map of which grid reference are required.
Grid references are always given with the eastings value first followed by the northing value; the grid reference of the intersection of the easting line 74 with northing line 33 is therefore 7433.
When giving a grid reference to a square, the reference is always to the southwest corner of the square. Thus the reference to the square in which A falls in Fig 4.1 is 7433. Similarly, B falls in square 7632.
Grid reference with a square (6/8 fig gird reference)
To provide an accurate grid reference to a point of details it is necessary to break up the grid square shown on the map into ten subdivision in each direction as shown in Fig 4.2. This shows the details within the square 7632 containing the points B that is a bridge.
The center point of this bridge is in the small square whose southwest corner id 7/10 east of easting 76 and also 7/10 north of northing 32. Its easting is thus 76.7 and is northing 32.7 units. Omitting the decimal points, the grid reference is thus written as 767327. |
