Measurement of Horizontal and Vertical Angle - Memorial University ...

ENGI3703- Surveying and Geomatics Fall 2007
Lab 3: Measurement of Horizontal and Vertical Angle
Objective: To motivate the students to use the techniques and present the concepts of angles
and coordinates.
Preparation: Read chapter 8 in the Elementary Surveying, 11 th ed. Textbook.
Overview: Determining the relative position of points often involves measurements of both
angles and distances. Therefore it is necessary to measure angles to a relatively
high level of accuracy.
Instruments to be used: Check out the following equipment:
Procedure:
Memorial University of Newfoundland
1. Transit or repeating Theodolite
2. Tripod
3. Two range poles
4. Five pegs
5. Plumb bobs
1. Students are divided into groups. Each group does the prescribed exercise.
Each student records his/her own measurements in his/her field book.
2. Lab instructor will demonstrate setup and operation of the theodolite.
3. Using the provided transit or theodolite set up the instrument over a point
(assigned by the instructor). Choose four other different points around 360 0
sweep. Use one of the chosen points as starting point (as a reference).
4. Measure and record the clockwise horizontal angles between the reference
point and the other three chosen points with the provided instrument. Make
one set of measurements with normal scope position and another one with
turned over (‘Plunged’) position.
5. Follow these steps when turning each horizontal angle:
a. Allow two persons at both the backsight point and foresight point to
hold the range poles above the chosen points.
b. Set the horizontal circle to 0º 00’ 00”
• For initial setup, align the upper motion mark and
intermediate plate mark. While looking through the reading
sight, slowly adjust the plate until the view reads zero (see
illustration below). Lock the upper motion and adjust by
rotating the upper motion adjustment dial.
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ENGI3703- Surveying and Geomatics Fall 2007
Classroom work:
Memorial University of Newfoundland
c. Sight the backsight using the LOWER MOTION
• Lock the Lower motion and adjust until the vertical crosshair
splits the string line of your rodperson.
d. Turn to the foresight using the UPPER MOTION
• Unlock the upper motion and advance to your foresight point.
Use the lock and adjustment on the upper motion only.
e. Record horizontal angle to the nearest ¼ minute (15”)
f. Turn the telescope in “Plunged” position and backsight using the
LOWER MOTION
• Unlock the lower motion and turn back to your backsight
point. Lock and adjust using only the lower motion. You will
notice your reading will not change during this step.
g. Turn to the foresight again using the UPPER MOTION, using the
same instructions as before to turn to the foresight point.
h. Record second horizontal angle, which should be double the first
angle.
i. Divide the second reading by two (2) and compare with the first
reading (should be within 30” of the first reading)
6. Choose a point situated well above the ground and with the transit or with the
theodolite measure the vertical angle between the horizontal plane and the top
of the confederation building.
Note:
♦ Make it sure the instrument is leveled properly before measurements.
♦ Original measurements are to be documented (including a sketch) in the
field book.
1. Calculate the sum of all angles, and check against 360 0 .
2. Summarize your data and provide average angles measured with the
instrument by you and by other members of your group.
3. Evaluate your results by comparing the average angle obtained by your group
members.
4. Evaluate the errors you may have committed during measurements.
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ENGI3703- Surveying and Geomatics Fall 2007
Memorial University of Newfoundland
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