CE 111 Circular Curve Lab
Spring 2005
Objective: Develop skills in determining positions of circular curves for field layout
using standard taping techniques and off-curve EDM measurements. Apply knowledge
of spreadsheet development learned in traverse laboratories to compute circular curve
coordinate and layout data for field survey.
Data
PI Station = 32+ 30.30 with coordinates of 170.34E, 284.51N (your coordinate values
and distances only need to be shown to the nearest 0.01 foot).
Azimuth of BC to PI tangent = 30O 00’ 00”
Delta = 36O 00’ 00” and the curve is to the right
D = 8O 00’ 00
Computations required
1) Complete sufficient manual computations of the circular curve to identify the
following:
 BC and EC stations around the curve, as well as the EC station coming along the
tangent.
 Deflection angle from BC to station 34+00
 Coordinates of Station 34+00
2) General spreadsheet
A basic spreadsheet layout with initial computations will be provided by the
instructor. You are to complete the spreadsheet, and are encouraged to add your own
layout and testing procedures. The final product must be general such that any curve to
the right or to the left could be solved using the basic data. The program must include
the flexibility of computing deflections and coordinates at uniform partial station
distances such as 30+ 25.00, 30+50.00, 30 + 75 in addition to the full station. (Your
instructor has already incorporated this flexibility for you, be sure you understand what is
being accomplished.)
This type of general program is often useful when solving design problems where it is
necessary to fit a curve to meet fixed conditions.
3) Angle and distance measurements for EDM
The surveyor found a convenient location in the field to use to set out the curve
from a single point that was not on the curve. The following measurements were made
from this position to two control points A and B, with the instrument at I.
Instrument at I. Distance IA = 477.86 feet, Distance IB = 499.26 feet. Points A
and B were both west of the instrument. The angle AIB was 85O 19’ 00”.
a)
In the office the coordinates of the control points were found to be:
A: 398.44 E, 215.65 N
B: 432.66 E, 877.13 N.
Calculate the position the surveyor plans to occupy by using two strategies:
1. Use the measured distance data in conjunction with the calculated AB distance
2. Use distance AI and the measured angle.
Distance BI and AB, plus angle AIB could be used to provide a third estimate of point I
coordinates. If we had multiple measurements from point I we could use a “least
squares” statistical approach to find the best estimate of the instrument position.
However, for our purpose, the average of the above two values will be used for the
proposed instrument location.
b)
Using the coordinates from part a, establish a table to show the azimuth and
distance from the instrument to points A and B and all the curve points including the PI,
BC, EC, and every half station along the curve.
The data in this table could be used in the field as follows:
Surveyor Jacobs occupies the instrument station and sets the I to A azimuth on the
horizontal angle scale and sights point A. Once this is set, the horizontal scale is
“released” and the scope is turned until the desired azimuth of another point is found.
The prism operator marks the position at the required distance along this azimuth line,
and sets the desired point.
Report
Provide the development of your solution of the problems and a printout of your
program results. Show your program to the instructor or lab assistant. Random changes
in the program will be made to check that new correct values are found as the input data
are changed.