1. Leveling
Intro to Leveling

2. Why do we level?
To determine elevation with respect to an imaginary level surface (geoid)
Leveling allows you to tie the depths acquired with the sonar to the geoid
Vertical control is established to provide a basic framework for large mapping projects, to establish new
vertical control in remote areas, or to further densify existing vertical control in an area. The purpose of
vertical control surveys is to establish elevations at convenient points over the project area. These
established points (benchmarks) can then serve as points of departure and closure for leveling operations
and as reference benchmarks during subsequent construction work.
The NGS, NOS, USGS, other Federal
agencies, and many USACE commands have established vertical control throughout the CONUS. Unless
otherwise directed, these benchmarks will be used as a basis for all vertical control surveys. Descriptions
of benchmark data and their published elevation values can be found in data holdings issued by the
agency maintaining the circuit.

3. Leveling

4. Equipment Level – An instrument used for measuring vertical distances
With differential leveling, differences in elevation are measured with
respect to a horizontal line of sight established by the leveling instrument. Once the instrument is leveled
(using either a spirit bubble or automated compensator), its line of sight lies a horizontal plane. Leveling
comprises a determination of the difference in height between a known elevation and the instrument and
the difference in height from the instrument to an unknown point by measuring the vertical distance with
3-wire level – stadia hairs allow you to calculate horizontal distance. The substadia lines in instruments meant for
three wire leveling are short cross lines that cannot be mistaken for the long central line used for ordinary
leveling
Crosshairs used to be spiderweb
a precise or semi-precise level and leveling rods.

5. Compensated level
Allows level to work correctly if not perfectly level
Easily damaged

6. Level rod
A long brightly painted rod, accurately calibrated in metric units (or feet and inches), used for obtaining elevations and stadia measurements of distance in mapping with a major surveying instrument.

7. Leveling terminology
Backsight - reading on a rod that is held on a point whose elevation has been previously determined
Foresight - reading on a rod that is held at a point whose elevation is to be determined 1 2 3 1 2 3
BM A
BM B

8. Leveling terminology cont.
Turning point - a temporary point whose elevation is determined by additions and subtractions of backsights and foresights respectively. 1 2 3 1 2 3
BM B 1 2 3
BM A

9. Leveling terminology cont.
Bust – Error is outside of tolerance for comparison of the forward run to the backward run
Blunder – Gross error caused by human mistake
Thread Interval- Difference between upper thread and middle thread, lower thread and middle thread
Thread error- Inaccurate reading of rod resulting in greater than 2mm difference between thread interval

10. 11 10 09 08 SAMPLE ROD READING TOP THREAD = MIDDLE THREAD =
BOTTOM THREAD =
0937
0892
0848
1048
1003
0960
1162
1118
1072 11 10
This method can be used for most types of leveling work and will
achieve any practical level of accuracy.
Three wire leveling can be applied if the
reticule of the level has stadia lines and substadia that are spaced so that the stadia intercept is 0.3 foot at
100 feet, rather than the more typical 1.0 feet at 100 feet. The substadia lines in instruments meant for
three wire leveling are short cross lines that cannot be mistaken for the long central line used for ordinary
leveling.
the rod is read at each of the three lines and the average is used for the final result. Before each
reading, the level bubble is centered. The half-stadia intervals are compared to check for blunders. 09
Note: Tread interval from top to middle = 45 and middle to bottom = 43. Ideally, the thread intervals should be equal, however this seldom occurs in the field. Thread intervals for 3rd order levels should match within 2 therefore, this would be an acceptable reading. 08

11. Importance of balancing
3 – 3 = 0 1 2 3 BM 1 2 3 BM
Also important for collimation
Distance X
Distance Y
Distance X

12. Bird’s eye view of a standard level run
Backward Run
Forward Run -5 +5
SPUR
SPUR -5 +5 +2 +2 -4
Most level operations require a line of sight less than 300 or 400 feet long
The leveling operation consists of holding a rod vertically on a point of known
elevation. A level reading is then made through the telescope on the rod, known as a backsight (BS),
which gives the vertical distance from the ground elevation to the line of sight. By adding this backsight
reading to the known elevation, the line of sight elevation, called "height of instrument" (HI), is
determined. Another rod is place on a point of unknown elevation, and a foresight (FS) reading is taken.
By subtracting the FS reading from the height of instrument, the elevation of the new point is established.
After the foresight is completed, the rod remains on that point and the instrument and back rod are moved
to forward positions. The instrument is set up approximately midway between the old and new rod
positions. The new sighting on the back rod is a backsight for a new HI, and the sighting on the front rod
is a FS for a new elevation. The points on which the rods are held for foresights and backsights are called
"turning points." Other foresights made to points not along the main line are known as "sideshots." This
procedure is used as many times as necessary to transfer a point of known elevation to another distant
point of unknown elevation -2 -2 -3 +4 +3

13. Bird’s eye view of a “RAINIER” level run
Backward Run
Forward Run -5 +5
SPUR
SPUR -5 +5 +2 +2 -4
Most level operations require a line of sight less than 300 or 400 feet long
The leveling operation consists of holding a rod vertically on a point of known
elevation. A level reading is then made through the telescope on the rod, known as a backsight (BS),
which gives the vertical distance from the ground elevation to the line of sight. By adding this backsight
reading to the known elevation, the line of sight elevation, called "height of instrument" (HI), is
determined. Another rod is place on a point of unknown elevation, and a foresight (FS) reading is taken.
By subtracting the FS reading from the height of instrument, the elevation of the new point is established.
After the foresight is completed, the rod remains on that point and the instrument and back rod are moved
to forward positions. The instrument is set up approximately midway between the old and new rod
positions. The new sighting on the back rod is a backsight for a new HI, and the sighting on the front rod
is a FS for a new elevation. The points on which the rods are held for foresights and backsights are called
"turning points." Other foresights made to points not along the main line are known as "sideshots." This
procedure is used as many times as necessary to transfer a point of known elevation to another distant
point of unknown elevation -2 -2 -3 +4 +3

14. Sample Level Run UNBALANCED BM B is 1 m below BM A _ BS 2 FS 2 1 2 3 11 2 3 TP _ TP BS 1 FS 3 1 2 3
The difference in elevation = 0 + (-2) + 1 = -1 m _
What is the difference in elevation between BM A and BM B? BS 2 FS 1 1 2 3
BM B is 1 m below BM A
Distance X1
Distance X1
Distance X2
BM A
BM B
Difference in Elevation = -2 m
Distance X2
Distance X3
Distance X3
Distance Y
Distance X3
Difference in Elevation = +1 m
UNBALANCED

15. Error

16. Parallax

17. Collimation
Collimation – the accuracy of the alignment of the optics of the level. Poor collimation will result in gross errors and possibly a bust. 1 2 3
No instrument is perfectly aligned.
to determine, against a
standard of accuracy, whether the instrument is properly adjusted;
and to compute a factor to correct balanced and unbalanced setups

18. Kukkamaki setup
Allow instruments to acclimate to ambient temperature for at least 10 minutes!! 1 2 3 1 2 3
10m
20m
10m
20m

19. ) ) ) ) ) Paper Kukkamaki - Collimation Check Kukkamaki
3rd 1
sum ) mm
BS1
sum ) mm
FS1
C = ( h h2 ) mm
20 m 1
BS1 - FS1 = h1
BS2 - FS2 = h2
where 2
sum ) mm
BS2
sum ) mm
FS2
10 m
ROD 1
ROD 2
SET UP 1
BS 1
FS 1
20 m
SET UP 2
BS 2
FS 2
KUKKAMAKI COURSE & SET UPS )
= Difference
h = Height
BS = Backsight
FS = Foresight
C = Collimation Error
Instrument SN:
Rod SN:
Party Chief:
Observer:
Recorder:
Rod Person:

20. ) : 2 1929 Kahului 161 5680 1 1 No 9 196 11/24/98 Difference < 30
2 1929
No 9 196
11/24/98
Difference < 30
1724
1654
1583
Difference < 2
1620
1548
1477 1 2
1653.7 mm 70 71 75 73
1548.3 mm 72 71 80 79
1) Sum all thread readings in
BS column.
2) Sum all thread readings in
FS column.
3) BS - FS
4) Divide by 3
5) Convert to meters
DE Computation
4961 mm
141 mm
+ 148 mm
289 mm
4645 mm
143 mm
+ 159 mm
302 mm
1628
1553
1480
1649
1569
1490 +
4661 mm +
4708 mm BS
9622 mm FS
9353 mm
BS - FS =
9.622 m m m m m
0.289 m m
0.591 m x m
1000
0.196 km
Distance Computation
1) Sum all THREAD INTERVALS.
2) Multiply by the Instruments Stadia.
3) Convert to Km.
Tip for Quick Mean
0.269 m )
1 = mm
2 = mm
Top Interval > Bottom Interval, then add to Middle Hair
Top Interval < Bottom Interval, then subtract from Middle Hair 3
Stadia m :
check
- (FORWARD RUN + BACKWARD RUN) m m m
0.20 km
Always use smallest distance

21. 1668
1592
1518
4778 mm
1612
1542
1471
4625 mm
1722
1716
1711
5149 mm
1692
1612
1532
4836 mm
1562
1489
1417
4468 mm
1664
1659
1653
4976 mm 9 10 11 mm mm mm mm 80 73 72 5 6 mm mm mm mm 76 74 70 71 6 5
160 mm
+ 145 mm
+ 11 mm
316 mm
150 mm
+ 141 mm
+ 11 mm
302 mm + + mm mm
BS - FS = m m
0.272 m 3 m
4.7600 m
0.316 m m
0.618 m x m
1000
0.205 km )
Stadia
check )

22. Paper leveling made easy!
Newiz
Paper leveling made easy!

23. Run