Unitec Institute of Technology
Land Surveying 2 (2015)
(ENGG & DE6207)
Assignment No. 2
(10% of total course)
“Precise Levelling
Observations,
Reductions & Analysis”
Due Date: 20 April 2015
Introduction
Precise Levelling is one of the functions a surveyor can be required to undertake as
part of the process of establishing reliable height information on a project. Nearly all
construction & infrastructure projects require reliable level and height information, to
varying degrees of precision and accuracy. It is common for such information to be at
the high end of the accuracy scale, requiring suitable techniques and instrumentation to
establish reliable and accurate values.
Accordingly, as with construction setout, precise levelling is an important skill to
understand and learn.
Correct and accurate level information is required for different purposes, some examples
of which are as follows:
 For overall, project network control purposes.
 To enable setout height information to meet certain tolerance limits.
 Monitoring purposes as part of any post construction phase, or where such
monitoring is required during specific parts of construction.
As per normal surveying practice, reduced level information supplied by the surveyor
must be correct. As such, it is vital that independent checks are completed as part of the
observation process to ensure such reliability. In general, the main criterion is to have
sufficient redundancy to ensure any gross errors are found and rectified. This is normally
achieved by completing independent check observations and measurements.
Assignment Details
For this assignment, you will be required to complete a full set of precise levelling
observations in terms of established Unitec benchmarks C2A & Y5. In addition, you are
required to observe to marks C3, C4, C5 & C6, Y6A as part of the observational
process, with the aim of deriving final reduced level values for these marks in terms of
the LINZ 2V order level origin values provided herein.
The field levelling observations will be completed in groups of 3, however every team
member must complete their own precise levelling observation-run between BMs, and
be involved in assisting their team members to complete theirs, by holding the levelling
staff in a vertical and stable manner, and measuring and monitoring distances between
change points as required. Note that this includes the completion of a separate 2-peg
collimation-calibration test before the completion of each observation period.
Results are to be processed and analysed on an individual basis, with individual
reports submitted for assessment purposes. If you miss this initial calibration test
requirement, you will need to redo all your levelling observations, so don’t forget !
Observing Specifications
The following requirements apply:
 Use double run levelling.
 Use the “BF-FB Line Levelling” method of levelling.
 Maximum 25m for each forward/backsight distance.
 Sight and Crest Clearance (except on elevated PRMs).
 Sight Distances.
 Sight Imbalances.

Height Misclosure of Run.
≤ 0.5m
5m ≤ D ≤ 25m
I ≤ ± 0.5m
ΣI ≤ ± 2.0m
Δ ≤ ± 2mm x √L
where D is the sight distance, I is the single set-up sight distance imbalance, L is the
approximate length (in Kilometres) of the levelling run and Δ is the misclosure.
A “Run” is closed when you return to (FS) the benchmark where you first started the BFFB line levelling sequence.
Field observations will need to form a closed-loop in both directions between the
specified benchmarks, with appropriate attention paid to minimising errors, such as
collimation, equalising backsights and foresights and the like.
Equipment
Each group should ensure that they have the following levelling equipment:
 1 x Digital Level (with at least 2 x instrument batteries)
 2 x Digital Level Staves with staff bubbles (if windy: bring support poles)
 1 x Tripod (sturdy)
 1 x Field Bag:
 2 x Change Plates (minimum);
 30 m tape;
 Chalk
The precise levelling instruments (Leica DNA03, or Trimble DiNi)) will be available for
completion of this assignment, although you will need to book them through David
Poyner (Unitec Survey Technician) to ensure all groups have access to the equipment to
allow completion of the field work as necessary.
Practical Procedure
Details of the operation of the digital level to complete this practical assignment have
been provided during the lectures. Practical procedure details are as follows:
 Each group will be allocated the same level run, which will be approximately
0.7km long. The run will connect the two existing BMs, and there are a series of
five new BMs along the route to be observed.
 Duties of observer, booker, and staff person are to be rotated, with one complete
run to be undertaken by each group member.
 A collimation check of the level is required, before levelling commences and
immediately after the completed levelling operation. The results of these
collimation checks are to be included within the final report.
 Change Point (CP) setting out is to be shared and should be carried out in the
most effective manner.
 The levelling staves need to be handled with care – only extend as far as
required. Caution must always be taken with regard to your own safety,
pedestrian safety and when working alongside roadways. It is the responsibility
of all members of the field party to ensure appropriate safety measures are in
place, and due care and attention is paid to identification of hazards. Correct
PPE must be worn at all times during this field assignment.
 Further, it is essential that the levelling staves are held vertically and in a stable
manner at all times. This is necessary to avoid rework due to excessive
misclosure and to provide the best chance of achieving the required accuracies.
 Change-plates are to be used as CPs for the staves. Plates need to be seated
by (gently) stepping on the change-plate supplied to ensure a stable platform for
the staff.
 Upon commencement of your levelling runs, initially allow the levelling instrument
to adapt to the ambient temperature prior to commencing work;
 The observer assumes control of operations and should determine what length
sight-distances will be used when setting out. Some factors to be considered are:
wind, air pollutants, heat shimmer and access roads. The observer will indicate
when staff personnel can remove their staves, pins, or change-plates.
 It is desirable to carry out observations at a consistent and even pace, at each
set-up.
Benchmark Information
Benchmark Approx. Northing
Approx. Easting
Point C2A
Point Y5
395135mE
394717mE
799872mN
799892mN
Reduced Level (Ak
MSL Datum 1946)
27.9307m
23.0241m
Precise levelling data can be processed using the levelling module within the Leica Geo
Office programme (version 8.3) for which Unitec has licences currently operating. These
can be accessed via any of the computer labs.
Figure 1 – Unitec site & levelling mark locations
Report Format
This assignment is to be presented using a short report structure using a conventional
word processing package.
The various elements to be contained within this format are as follows:
 Levelling methods and processes utilised.
 Relevant group details, observation dates, etc
 Reduction of data (to enable final results to be determined).
 Independent field checks completed and levelling closures achieved.
 Processing of results through appropriate software package.
 Presentation of final precise levelling results for the three unknown marks.
 Summary & conclusions
Note that presentation is again important, so make the effort to submit a report of
suitable quality and content.
Total mark for this section of the assignment will be 10% of the total course mark.
Due date for this assignment will be 20 April 2015, by 1:00pm.