How to calculate gradient
Rise/Run = vertical height/horizontal distance
eg: road = 110m
sch = 8m
distance = 5.1km
110m-8m/5.1*1000= 102/5100= 50
1:50
How to convert from:
ft-miles
miles-km
km-miles
- *0.305
- 1.609
3.1000
The formula used to calculate Gradient (Slope)
Gradient = Vertical Interval (V.I.) \div Horizontal Equivalent (H.E.)
What does the Vertical Interval (V.I.) represent?
The difference in height (elevation) between the two points
What does the Horizontal Equivalent (H.E.) represent?
The true horizontal distance between the two points on the ground
First crucial step in the Gradient calculation process
Determine the Vertical Interval (V.I.) by subtracting the lower contour reading from the higher reading.
Second crucial step in the Gradient calculation process
Determine the Horizontal Equivalent (H.E.) by converting the measured map distance to ground distance using the scale.
Third crucial step in the Gradient calculation process
Ensure both V.I. and H.E. are in the same unit (e.g., both meters or both kilometers).
If V.I. = 100m and H.E. = 500m
state the final answer format for the gradient.
The required map feature used to determine the V.I.
Contour Lines (and the spot heights/benchmarks).
Rule for reading Easting grid lines
Read the number of the vertical line to the West (left) of the feature. Eastings run North-South.
Rule for reading Northing grid lines
Read the number of the horizontal line to the South (bottom) of the feature. Northings run East-West.
The order in which grid references MUST be read
Eastings first
Purpose of a 4-Figure Grid Reference
To locate a feature within a 1 square kilometer area (4-figure gives the bottom-left corner).
Purpose of a 6-Figure Grid Reference
To locate a specific feature within a 100 metre \times 100 metre square.
How to convert a 4-figure to a 6-figure reference (e.g.
from 4268)
Definition of Contour Line
A line on a map joining places of equal height above sea level.
What do closely spaced contour lines indicate?
A steep slope or gradient.
What do widely spaced contour lines indicate?
A gentle slope or gradient.
How do contour lines indicate a river valley?
They form a V-shape
1st Point (0°/360°)
North (N)
2nd Point (22.5°)
North North East (NNE)
3rd Point (45°)
North East (NE)
4th Point (67.5°)
East North East (ENE)
