1. Data capture on the ground:
fundamentals of land surveying
Traditional survey techniques
Electronic and satellite based
techniques

2. Traditional Plane Surveying
• The measurement, recording and
calculation of the horizontal location of
details of the land, and the preparation
of maps from those records.

3. The basic parts of a plane survey
Detail
Station point
Control line
Control
framework
Detail line

4. Basic definitions
• Detail; the actual geographical entities of
interest
• Control framework; carefully measured
network of points and lines which tie together
detail measurements
• Control lines; carefully measured straight
lines making up a control framework
• Station points; points on a control framework
locating the ends of control lines.
• Go from the whole to the part: control to
detail

5. The whole: control frameworks
Chain survey:
control framework
built of triangles
Traverse survey:
control framework
of lines and angles
between the lines

6. The part: detail measurements
Station point
Control line
Station point
Detail line: tie line Detail line:offset line
part of a triangle at right angles to control line

7. Drawing up the survey
First draw the control line
-then draw the detail lines
-then join the dots

8. Height surveying equipment

9. Spirit levelling: measuring relative heights directly.
Automatic level
on tripod
Horizontal line of sight

10. Spirit levelling: measuring relative heights directly.
4m levelling staff
4m
3.1
Automatic level
on tripod
0m Horizontal line of sight

11. Spirit levelling: measuring relative heights directly.
3.1 2.9
Automatic level
on tripod
0m Horizontal line of sight

12. Spirit levelling: measuring relative heights directly.
4m
3.1 2.9 3.0
Automatic level
on tripod
0m Horizontal line of sight

13. Spirit levelling: measuring relative heights directly.
4m
3.1 2.9 3.0 2.1 1.6 0.5
Automatic level
on tripod
0m Horizontal line of sight
The difference between any two readings is the relative
difference in height between those two points

14. Relative heights and reduced levels
• The relative height between Cirencester and Birdlip is
surveyed at 98.7m
Birdlip
98.7m
Cirencester

15. Relative heights and reduced levels
• The relative height between Cirencester and Birdlip is
surveyed at 98.7m
• The height of Cirencester above Mean sea level is
known to be 127.3 m, its “reduced level above datum”
Birdlip
98.7m
Cirencester
127.3m
Mean sea level=0.0m
(The datum level)

16. Relative heights and reduced levels
• The relative height between Cirencester and Birdlip is
surveyed at 98.7m
• The height of Cirencester above Mean sea level is
known to be 127.3 m, its “reduced level above datum”
Birdlip
98.7m
Cirencester
127.3m 226.0m
Mean sea level=0.0m
(The datum level)
• The reduced level of Birdlip is Cirencester’s reduced
level plus the relative height between the two towns
127.3 + 98.7= 226.0m

17. Converting relative measurements to reduced levels
Add or subtract sequential relative heights from previous reduced level
4m
3.1 2.9 3.0 2.1 1.6 0.5
102.6m
101.5m
101.0m
100.2m 100.1m Height above datum of
100 m AMSL 0m 100m one point is needed
(Above Mean Sea Level
OS datum (msl)

18. Ordnance survey datum level and bench marks
OS public bench mark
OS fundamental
bench mark
Levelled height
survey
Newlyn:
OS tidal station =
OD Cirencester
127.3m AOD

19. Measuring large changes in height in small steps
• Big changes in height measured by
adding/subtracting lots of small
changes
• Two bits of equipment used
– The “level” on a tripod
– The survey staff
Birdlip
staff
level ?
a
Cirencester

20. Measuring large changes in height in small steps
• Big changes in height measured by
adding/subtracting lots of small
changes
• Two bits of equipment used
– The “level” on a tripod
– The survey staff
Birdlip
staff
level ?
b
a
Cirencester

21. Measuring large changes in height in small steps
• Big changes in height measured by
adding/subtracting lots of small
changes
• Two bits of equipment used
– The “level” on a tripod
– The survey staff
Birdlip
staff
level ?
b
a
Cirencester

22. Measuring large changes in height in small steps
• Big changes in height measured by
adding/subtracting lots of small
changes
• Two bits of equipment used
– The “level” on a tripod
– The survey staff
Birdlip
staff
level ?
b
a
Cirencester

23. Measuring large changes in height in small steps
• Big changes in height measured by
adding/subtracting lots of small
changes
• Two bits of equipment used
– The “level” on a tripod
– The survey staff
Birdlip
staff e
d
level c ?
b
a
Cirencester

24. Measuring large changes in height in small steps
• Big changes in height measured by
adding/subtracting lots of small
changes
• Two bits of equipment used
– The “level” on a tripod
– The survey staff
Birdlip
staff e
d
level c ?
b
a
Cirencester ?=a+b+c+d-e

25. Measuring large changes in height in small steps
• Big changes in height measured by
adding/subtracting lots of small
changes
• Two bits of equipment used
– The “level” on a tripod
– The survey staff
Birdlip
staff e
d
level c ?
b
a
Cirencester “change points” ?=a+b+c+d-e

26. Accuracy of this simple technique
• Great Trigonometrical Survey of India, 1802 – 1832
• Height accuracy at Nepalese, compared to starting
point in Madras, was 6”
Maps © Royal Geographical Society

27. Trigonometrical leveling: relative heights calculated
target
Theodolite (measures
horizontal and
vertical angles) L
h
o
d
h=Lsin o
Knowing L is the tricky part.
This is now measured electronically

28. Electro-optical distance measurement (EDM)
IR pulse returns to unit. Distance is calculated from the
time difference between transmission and reception of IR
pulse
EDM unit
Right angled
EDM unit sends a reflector (corner
focussed pulse of Infra- cube)sends IR
red (IR) radiation beam directly
back to EDM unit

29. EDM used to monitor Mount St Helens
• EDM stations are
permanently established
• At regular intervals
measurements are taken
between these stations
• Changes in measurements
show change to the shape of
the volcano

30. Electronic Field Equipment
• Electro-optical distance measuring
(edm) device
• Electronic theodolite that measures
angles automatically
• Both are now usually combined into a
single unit known as a total station or
to give it its technical name
electro-optical tacheometer

31. Total station equipment

32. Trigonometrical surveying with EDM based “Total station”
reflector
Total station:
measures L by EDM
and o electronically L
h
o
d
h=Lsin o
Knowing L is now easy. Total station
automatically calculates h and d
d=Lcos o

33. Laser surveying
• Light
• Amplified
• Stimulated
• Emission of
• Radiation
• LASER beams are coherent and do not
disburse, so can travel enormous
distances and still remain visible
Light
Laser

34. Laser distance measurement
• LIDAR: LIght Detecting And Ranging
• Visual equivalent of RADAR
• LASER based EDM where distance
from LASER unit to point at which it
strikes and object is measured and
recorded

35. LASER scanning
• LIDAR based LASER Scanner scans a
series of laser pulses over the surface
of distant object.
• By measuring the distance of each point
scanned and the angle to the scanning
beam, the location of the scanned point
can be calculated and displayed in 3-D,
creating a “point cloud” image of the
object

36. LASER scanning output