New Geography in Action Junior Cycle Geography Calculating area
Finding the area of a region or feature on a map can be done in two different ways. This depends on the shape of the area in question. Regular area
Top Tip
This can be in the shape of a rectangle or square area on the map. We calculate the area by counting the total number of grid boxes. You can also multiply the number of squares across by the number of squares down. Your answer must then be converted to km².
Irregular area
This is the shape of a non-rectangle or square area, for example a harbour or a lake. To get the area we must first count the full boxes that are taken up by the harbour or lake. We then count any boxes that are half or more covered by the harbour or lake. To finish, we add the two together and give the answer in km² approx.
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We learned in Chapter 1 that the scale on Ordnance Survey maps is 2 cm to 1 km. Every box on the grid is 1 km by 1 km. This makes each grid box 1 km² in area.
See Video 6: Calculating area: Regular area
See Video 7: Calculating area: Irregular area
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NUMERACY ACT VITY
Look at the OS map of Bray above. (i) Can you calculate the area of the map in km²? (ii) Calculate the area of water on the map in km².
