calculating area on topographic maps. area of a square formula area = length x width
TRANSCRIPT
Calculating Area on Topographic Maps
Area of a Square
FormulaArea = Length x Width
Calculating the area of an even boundary
A map with a scale of 1:50 000. The length of this map is 5cm and the width is 3cm. Calculate the area represented by the map. Convert the length and width into what they represent in
reality before using the formula*. Scale 1:50 000 - therefore each cm on the map
represents 0.5 km in reality Length: 5cm x 0.5 km = 2.5km
Width: 3cm x 0.5 km = 1.5 km Area = Length x Width = 2.5km x 1.5km = 3.75 sq.
km
Calculating the area of an uneven boundary
Calculate the area of Klinger Lake.
How to do it…
Step 1: Work out the area of one grid square on the map. Scale of this map: 1:50 000, therefore each cm
represents 0.5km Length: 2cm x 0.5km = 1.0km Width: 2cm X 0.5 km = 1.0km Area of One Grid Square = 1.0km x 1.0km = 1.0 sq. kmStep 2: Determine the number of squares that the object
occupies. Klinger Lake occupies a total of about 0.5 of a grid
square.Step 3: Multiply the number of grid squares that the object
occupies by the area of one grid square. Hence, 0.5 of a square x 1.0 sq. km = 0.5 sq. km which
is the area of Klinger Lake.
Another way to do it…
Calculate the area of the built up portion of the city (i.e. the pink shaded area).
Working with Percentages…
Step 1: Work out the area of one grid square on the map. It is the same as the previous map: 1.0 sq.km.Step 2: Determine the number of squares that the object
occupies. In this situation, one could go from grid square to grid
square determing how much the built up area occupies each square.
i.e. 0.1 of a grid square (5866) + 0.4 (5966) + 0.7 (5967) + 0.7 (6067) + 0.03 (5868) + 0.5 (5968) + 1.0 (6068) + 0.25 (6168) + 0.2 (5869) + 0.6 (5969) + 1.0 (6069) + 0.85 (6169) + 0.2 (6269) + 0.8 (6070) + 0.85 (6170) + 0.2 (6270) + 0.2 (6071) + 0.4 (6171) = 8.98 squares
Step 3: Multiply the number of grid squares that the object occupies by the area of one grid square.
Hence, 8.98 squares x 1.0 sq.km = 8.98 sq. km which is the area of downtown St. John's.