TAPE CORRECTIONS
Lecture 4
GE 10: GENERAL SURVEYING I
Department of Geodetic Engineering (DGE)
Training Center for Applied Geodesy and Photogrammetry (TCAGP)
College of Engineering, University of the Philippines, Diliman
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Tape Corrections in Geodetic Engineering: Rules, Causes, and Equations, Study Guides, Projects, Research of Engineering
An in-depth look into tape corrections in geodetic engineering. It covers the rules for tape corrections, causes of errors, and equations to apply for each correction. Topics include corrections for tape not of standard length, slope, alignment, temperature, tension, and wind.
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2021/2022
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TAPE CORRECTIONS
Lecture 4
GE 10: GENERAL SURVEYING I
Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman
Objectives
By the end of the lecture the students should be
able to:
- Identify, enumerate and apply correctly the
rules and general statement for tape corrections
- Discuss the causes of errors in taping and
carry out corresponding corrections
- Determine equations to apply for each tape
correction
Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman
Tape Corrections
Department of Geodetic Engineering (DGE)Training Center for Applied Geodesy and Photogrammetry (TCAGP)College of Engineering, University of the Philippines, Diliman 4
Rules in Tape Corrections
5
First Rule:
When a line is measured with a tape that is “TOO LONG” , corrections are ADDED
Second Rule:
When laying out a length with a tape that is “TOO LONG”, corrections are SUBTRACTED
Third Rule: When a line is measured or laid out with a tape that is “TOO SHORT”, corrections applied are opposite of 1st^ and 2 nd^ rules Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman
Corrections to Tape
7
- Due to tape not of standard length
- Due to Slope
- Due to Alignment
- Due to Temperature
- Due to Tension
- Due to Sag
- Due to Wind Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman
Often due to imperfections in their manufacture
Also due to constant use of tapes becoming
worn, kinked, and improperly repaired when
breaks occurred.
Corrections may vary from few millimeters or
centimeters
Tape Not of Standard Length
Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman 8
CL = Corrected length of the line to be measured or laid out ML = length measured or laid out Corr = Correction per tape length (TL-NL) TL = True or Actual Length NL = Nominal Length of tape
NL
ML CL ML Corr
Tape Not of Standard Length
Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman 10
The length of line AB measured with a 50-m tape is
465.285 m. The tape used is found out to be 0.016 m
too long. Determine the correct length of AB.
Tape Not of Standard Length
11
Example
Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman
When distances are measured along a slope, the equivalent horizontal distance may correspondingly be determined by applying an approximate or exact slope correction
Due to Slope
13
h
d s C
Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman
3
2 4
2 8 s
h
s
h Ch
s
h Ch 2
2
Ch s 1 cos
Gentle Slopes (<20%)
Steep Slopes (Between 20% & 30%)
Very Steep Slopes (>30%)
Ch = slope correction = s-d h = Delev between pts s = measured slope distance d = equivalent Horizontal distance
h
d s C
(^14)
Due to Slope
Corrections to Tape
The slope distance of line AB is 76.52 m. The difference in
elevation is 30.55 m for points A and B. Determine the slope
correction for line AB assuming slopes are gentle, steep and
very steep.
ANSWERS:
Ch: gentle = 6.098 m, steep = 6.341 m , very steep = 6.363 m
16
Example
Due to Slope
3
2 4
2 8 s
h
s
h Ch s
h Ch 2
2 Ch s 1 cos
Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman
Linear error due to inaccuracy in alignment of a tape
Similar to the effect of slope
Easier to control and smaller in magnitude
Generally least important among different tape corrections
17
Due to Alignment
Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman
t s
C kL T T
Ct = Correction due to change in temperature k = coefficient of linear expansion (steel = 0.0000116/^0 C) L = length of line measured T = temperature of tape at time of measurements Ts = standard temperature of tape (usually 20^0 C)
19
Due to Temperature
A steel tape is known to be 50 m long at 20^0 C. The tape was used to measure a line 532.28 m long at 35^0 C. Determine:
a) Whether the tape is “too short” or “too long”
b) Ct per tape length
c) Ct total
d) Corrected length of line 20
Example
Due to Temperature
Department of Geodetic Engineering (DGE) Training Center for Applied Geodesy and Photogrammetry (TCAGP) College of Engineering, University of the Philippines, Diliman