DAR ES SALAAM INSTITUTE OF TECHNOLOGY

DEPARTMENT OF CIVIL ENGINEERING

TEST 1 EXAMINATIONS

SEMESTER II, 2023/2024

MODULE: CEU 07205 – CONTROL SURVEYING

BENG20-CE-1, BENG20-CE-2 & BENG20-CE-3

INSTRUCTIONS; ANSWER ALL QUESTIONS

(19/JUNE/2024) TIME ;0230 HRS

1. WRITE TRUE OR FALSE

I. Horizontal controls points serve as points of departure and closure for leveling
operations and as reference benchmarks during subsequent construction work.
FALSE
II. With Trigonometric leveling, differences in elevation are measured with respect
to a horizontal line of sight established by the leveling instrument. FALSE
III. Differential leveling is especially effective in establishing control for profile lines,
for strip photography, and in areas where the landscape is steep (mountainous).
FALSE
IV. “Employing higher quality instruments and more accurate staves, more rigorous
observing techniques, Restricted climatic and environmental conditions, refined
booking and reduction, least squares adjustment for a levelling net” should be
followed& adhered while conducting third order or less order levelling. FALSE
V. GPS satellites provide orthometric heights directly, which must be converted to
ellipsoidal heights using geoid models for accurate vertical control. Orthometric
heights are referenced to the Earth's ellipsoid, while ellipsoidal heights are
referenced to the geoid. FALSE
VI. Temperature changes during a differential leveling survey can introduce
systematic errors that affect the accuracy of height measurements. TRUE
VII. GNSS receivers directly measure Orthometric heights above sea level, eliminating
the need for geoid undulation corrections in elevation calculations. FALSE
VIII. Reciprocal leveling is a technique used to minimize errors in differential leveling
surveys by averaging the height differences observed from two directions. TRUE
IX. Differential leveling and GNSS can be used together in hybrid surveys to leverage
the strengths of both methods, achieving higher accuracy in elevation
determination. TRUE
 X. Integration of data from multiple sources, including GNSS, spirit leveling, and
other techniques does not optimize accuracy for height determination rather than
depreciating their accuracy. FALSE
XI. GNSS (Global Navigation Satellite System) leveling provides instantaneous and
accurate orthometric heights above sea level without the need for geoid
undulation corrections. FALSE
XII. The goal of leveling in setting out surveys is to establish a horizontal reference
plane for accurate positioning of structures and infrastructure elements in
construction projects. FALSE
XIII. Network design in control surveying focuses primarily on establishing precise
horizontal coordinates for survey control points, with less emphasis on vertical
control. FALSE
XIV. Post-analysis in surveying is unnecessary if data collection and measurements
were conducted accurately during the surveying process. FALSE
XV. Monumentation is an optional stage in control surveying that is only necessary for
large-scale projects or surveys covering extensive areas. FALSE
XVI. Monuments in Control survey are designed to be temporary and can be easily
relocated or replaced if their original location becomes inaccessible or obscured.
FALSE
XVII. Observation stage in control surveys focuses primarily on selecting and calibrating
survey instruments based on project specifications and accuracy requirements
FALSE
XVIII. The accuracy of data reporting in control surveys is primarily determined by the
speed at which survey data is compiled and delivered. FALSE
XIX. Precise leveling surveys are primarily used for establishing accurate horizontal
coordinates of survey control points, with less emphasis on vertical elevation
determination. FALSE
XX. Curvature and refraction corrections are necessary in precise leveling to account
for the Earth's curvature and atmospheric effects, ensuring accurate elevation
measurement TRUE

2.
a. How can an angular closure be computed on a link traverse? 1 marks

Calculation of angular misclosure by finding difference between the observed

bearings with the closing bearings.

 A1 +(angles) -(n – 1) 180= A2

 where A1 is the initial or starting bearing, A2 is the closing or final
bearing, and n is the number of angles measured.
b. Concisely elucidate significance of reconnaissance in establishing traverse
stations. 2 marks
Enable the optimizing (time, accuracy & cost) the traverse networks
Help attaining accuracy and precision

c. In a GNSS survey, point A has a geoid undulation of -30 meters and point B has a
geoid undulation of -28 meters. If the ellipsoidal height at point A is 110 meters
and at point B is 108 meters, calculate the orthometric height difference between
the two points. 4 marks

a) Understand the terms:

 Ellipsoidal Height (h): The height above the ellipsoid.

 Geoid Undulation (N): The difference between the geoid (mean sea
level) and the ellipsoid at a given point. A negative value indicates
the geoid is below the ellipsoid.

b) Given data:

 Ellipsoidal height at point A (hA): 110 meters

 Ellipsoidal height at point B (hB): 108 meters

 Geoid undulation at point A (NA): -30 meters

 Geoid undulation at point B (NB): -28 meters

c) Calculate Orthometric Heights (H):

 Orthometric height (H) is related to ellipsoidal height (h) and geoid

undulation (N) by the formula: 𝐻=ℎ−𝑁H=h−N

d) Calculate Orthometric Heights at Points A and B:

 For point A: 𝐻𝐴=ℎ𝐴−𝑁𝐴HA=hA−NA 𝐻𝐴=110−(−30)

 HA=110−(−30) 𝐻𝐴=110+30HA=110+30 𝐻𝐴=140HA=140 meters

 For point B: 𝐻𝐵=ℎ𝐵−𝑁𝐵HB=hB−NB 𝐻𝐵=108−(−28)

 HB=108−(−28) 𝐻𝐵=108+28HB=108+28 𝐻𝐵=136HB=136 meters

e) Calculate the Orthometric Height Difference:

 Now, calculate the orthometric height difference between points A

and B: Δ𝐻=𝐻𝐴−𝐻𝐵 ΔH=HA−HB Δ𝐻=140−136 ΔH=140−136 Δ𝐻=4
 ΔH=4 meters

3.
a. Among principles governing conduct of any survey work is called “working from
the whole to the part” precisely explain this principle. 3 marks
Precise controls surveying (Establishing of precise control points (The
establishment of two- or three-dimensional control networks) being the reference
controls points used as base for other works’
Thesea are series of points or positions which are spatially located for the
purpose of topographic surveying, for the control of supplementary points,
or dimensional control on site.
Following to subsidiary surveying works to locate, sett or detail surveying
by offsetting, triangulation, trilateration and etc.

b. To find the elevation of the top (Q) of a hill, a flag staff of 2 m height was erected
and observations were made from two stations P and R, 60 m meters apart. The
horizontal angle measured at P between R and the top of the flat staff was 60º 30'
and that measured at R between the top of the flag staff and P was 68º18'. The
angle of elevation to the top of the flag staff was measured to be 10º12' at P. The
angle of elevation to the top of the flag staff measured was to be 10º48' at R. Staff
readings on BM when the instruments was at P was 1.965 m and that with the
instrument at R was 2.055 m. Calculate the elevation of the top of the hill if that of
B.M. was 435.065 m. 7 marks
c. The top Q of a chimney was sighted from two stations P and R, at very different
levels, the stations P and R being in the line with top of the chimney.The angle of
eleveation from P to the top [ of the chimney was 38 deg 21 min and that from R
to the top of the chimney was 21deg 18 min. The angle of elevation from R to a
staff(vane) 2m above the foot of staff held at P was 15deg 11 min. The heights of
the instrument at P and R were 1.87m and 1.64m respectively. The horizontal
distance between P and R was 127 m and the reduced level of R was 112.78m, Find
the reduced level of the top of the chimney and the horizontal distance to the
chimney. 8 marks
4.
a) To expedite going down a hill, the back sight distances were consistently held to
100 m, while the foresight distances were held to 250 m. There were 46 setups. If
the observed elevation differences were −283.98 m, what is the elevation difference
corrected for Earth curvature and refraction? 3marks

b) A preengineering baseline was run down a very steep hill (Figure below). Rather
than measure horizontally downhill with the steel tape, the surveyor measured
the vertical angle with a theodolite and the slope distance with an EDM. The
vertical angle was 21°26, turned to a prism on a plumbed range pole 4.88 m above
the ground. The slope distance from the theodolite to the prism was 148.61 m. The
theodolite’s optical center was 4.669 m above the upper baseline station at 110
+71.25 m.
 i. If the elevation of the upper station is 324.28m, what is the elevation of the
lower station?
ii. What is the chainage of the lower station? 4marks

c) Trigonometrical levelling is carried out on a coastal site to transfer heights from

cliff top to beach. The following measurements are taken with a total station set at
control point A located at the top of the cliff to a reflector setup at control point B
on the beach.

Slope distance AB is 97.328 ± 0.005 m

Vertical angle from A to B is 15°57'05" ± 30"

The heights of the total station and reflector above points A and B are:
Height of total station above A 1.564 _±0.005 m
Height of reflector above B 1.420 ± 0.005 m

The height of point A is 29.639 ± 0.005 m

Calculate the height of B and its standard error.

If a better accuracy was required for the height of point B, which

measurement would you improve and why? 8 marks