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www.forest.umaine.edu
www.umaine.edu
College of Natural Sciences,
Forestry, and Agriculture
School of Forest Resources
Unifying Themes and Forests
Measuring Slope
June 23, 2009
by Bill Livingston
School of Forest Resources, University of Maine
Measuring slope is a common activity in when describing a forest habitat or when construction of a trail or road
is needed. In this exercise, we will compare three different methods for measuring slope and elevation change.
Objectives


Use a clinometer, range pole, tape measure, and GPS unit to measure slope and elevation change
Successfully use math to calculate the desired measurment
Materials
2 m range pole (can be made of PVC, photocopies tape measure taped to pole)
Clinometers (commercial or hand-made)
Tape measure (35-100 ft or 10-30 m)
GPS unit
Procedure
1) Learn to use the clinometers
a) Look through the site
b) Keep both eyes open
c) Read the scale on the inside of the clinometer with one eye and site the target with the other eye
2) Find the “eye” height
a) Hold the range pole at the same level as the person holding the clinometers
 You can use any carpenter’s level, but two people are needed. One person watches the level
bubble and lets the second person, who is sighting the range pole, know when the level is level.
b) Site the range pole with the clinometer until the scale shows “0”; read the height on the range pole
where the horizontal sighting line of the clinometers intersects it. This is the “eye” height of the
observer. Write the value in the table.
3) Go to a trail with a steep slope.
4) Range pole method
a) The person with the clinometers stands at the bottom of the slope.
b) The person with the range pole proceeds up the slope until the elevation gain is approximately the
same as the person’s height.
c) Site the range pole with the clinometer until the scale shows “0”; read the height on the range pole
where the horizontal sighting line of the clinometers intersects it. Write the value in the table.
d) Measure the distance from the person with the clinometers to the bottom of the range pole – keep the
tape measure on the ground. Enter the distance in the table.
e) The person with the clinometers goes to the point of the range pole and stands there.
f) Repeat steps d-g until the top of the slope is reached.
Page |2
5) Clinometer method
a) The person with the clinometer stands at the bottom of the slope.
b) The person with the range pole proceeds up to the top of the slope (or as far as the line of site will
allow).
c) Look through the clinometer and place the horizontal sighting line on the range pole at the height of
the “eye” height of the observer.
d) Read the angle on the clinometers scale and enter the value in the table.
e) Measure the distance between the clinometer and range pole. Enter the value in the table.
6) GPS method
a) Start at the bottom of the slope.
b) Turn on the GPS unit and wait until the geographic position is indicated on the screen.
c) Go to the page that gives you elevation and distance traveled. Reset the page so that the distance
traveled (or odometer) is set to zero.
d) Record the elevation.
e) Proceed to the top of the slope.
f) Record the elevation and distance traveled. The distance traveled is the horizontal distance, not the
distance up the slope.
g) Repeat the measures one or two more times.
Data
Page |3
RANGE POLE METHOD
Eye height = ______m
Height Elevation
on Pole Change
(m)
(Eye Height Height on Pole)
(m)
Point 1
Point 2
Point 3
Point 4
Point 5
Point 6
Point 7
Point 8
Point 9
Point 10
Point 11
Distance Horizontal
(m)
Distance (m) =
SqRt(Dist2—
ElevChng2)
Percent Slope
(Elev Change
/HorizDist)*100
Angle
(arcTan of
Percent slope)
Totals
CLINOMETER METHOD
Eye height = ______m
Angle
Distance (m)
Elevation
Change =
Sin(angle)*
distance
Horizontal
Distance (m) =
Cos(angle)*
distance
Percent Slope =
Tan(angle)*100
Point 1
Point 2
Point 3
Totals
----------------
Avg=
GPS METHOD
Elevation
bottom
(ft)
Trial 1
Trial 2
Trial 3
Averages
Elevation Elevation
top (ft)
Change
(ft)
Horizontal Percent Slope
Distance
(Elev Change
(ft)
/Dist)*100
Angles
(arcTan of Percent
slope
Page |4
Page |5
Class Results Table
Range Pole
Range Pole
Elevation
Percent
Change (m) Slope
Average
Range Pole
Clinometer
Clinometer
Clinometer
GPS
GPS
GPS
Horizontal
Distance (m)
Elevation
Change (m)
Percent
Slope
Horizontal
Distance
(m)
Elevation
Change (m)
Percent
Slope
Horizontal
Distance
(m)
Page |6
Questions
1. Which method was the most accurate? Explain.
2. Which method was least accurate? Explain.
3. Which method would you select to use in the future? Explain