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1. GRADIENT
How to calculate the gradient using a topological map
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2. Formula to be applied
• Gradient is an expression of the change in
elevation over the distance covered along the
surface.
• Gradient =
Vertical difference (in height)
Horizontal distance (on the ground)
• Express gradient in the format VD:HD
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3. example
Calculate the gradient of the road
from the bridge at Cocoa Estate to
the junction near the radio mast on
the coast.
(adapted from CSEC 2012 Geography CXC May/June – Qn 1(v))
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4. Dominica (Lesser Antilles)
Examine the contour lines that pass through each point for
the heights; and use the scale to ascertain the distance
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5. Steps to take
• Identify the heights of the two locations
• Measure the distance in a straight line between the
two points.
• OR if specified, along the route identified (e.g the road,
or river, etc)
• Ensure that both the height and the distance have
been expressed in the same units (i.e metres or feet)
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6. What do we now know?
• The height of the bridge is
65 metres
• The height of the junction is 5 metres
• The measurement of the distance between
the bridge and the junction is 3000 metres
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7. Applying the formula
•
Vertical difference (in height)
Horizontal distance (on the ground)
65 - 5
3000
•
therefore the gradient VD:HD
(60: 3000) is 1: 50
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8. sketched
For every fifty metres (in distance) you advanced from the
bridge towards the junction you would have descended one
metre (in height)
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