Surveying - St. Bonaventure University
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Transcript Surveying - St. Bonaventure University
Surveying
CS 128/ES 228 - Lecture 10a
1
Data for a GIS
Raster data
- characteristics?
- sources?
Vector data
- characteristics?
- sources?
Bottom: Elements of Surveying. U. S. Army, TM 5-232, 1971
CS 128/ES 228 - Lecture 10a
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History of surveying
Babylon: knew 3-4-5
triangle; developed
base-60 system
Egypt: used simple
plumb line sighting &
right-angle
instruments.
Great pyramid: base
square to 0.2 m out
of 230 (0.09%)
Top: The Roman Land Surveyors. O. A. W. Dilke, 1971
CS 128/ES 228 - Lecture 10a
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The motive for surveying?
The priests also said that this king
divided the country among all the Egyptians,
giving each an equal square plot. This was
the source of his revenue, as he made them
pay a fixed annual tax. If anyone’s land were
taken away by the river, he came to the king
and told him what had happened. Then the
king sent men to look at the land and
measure how much less it was, so that in
future the owner would pay the due
proportion.
Herodotus, referring perhaps to Sesostris II of
Egypt (1897-1878 BC). From: Dilke. The Roman
Land Surveyors. Barnes & Noble, NY. 1971.
CS 128/ES 228 - Lecture 10a
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Two types of surveys
Geodetic survey
- covers distances large enough that
curvature of Earth is significant
- establishes network of precisely
located control points
Plane survey [not ‘plain’]
- straight lines & angles are sufficient
- what about long, linear features?
CS 128/ES 228 - Lecture 10a
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National Geodetic Survey
Functions:
defines & manages
the National Spatial
Reference System
sets standards for
geodetic surveys
maintains a database
of U. S. geodetic
markers
www.ngs.noaa.gov
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NGSurvey data sheets
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Uses for plane surveys
Land survey
Engineering or
construction surveys
Field mapping
Top: Plane Table Mapping. M. Denny. www.pobonline.com...
Bottom: www.tpub.com/engbas/11-24.htm
CS 128/ES 228 - Lecture 10a
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Basic methods
Locating a point
Measuring an angle
Measuring a distance
Measuring differences
in elevation
CS 128/ES 228 - Lecture 10a
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Locating a point
Start with known
location or previous
point
Direction + distance
common for plane
surveys (ex. “metes
& bounds”)
Two angles common
for geodesy
Principles of Surveying. 2nd ed. C. A. Herubin, 1978
CS 128/ES 228 - Lecture 10a
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Measuring an angle
Horizontal angles:
use level, transit, or
theodolite
Vertical angle: use
transit or theodolite
Both: Principles of Surveying.
2nd ed. C. A. Herubin, 1978
Either:
- graduated circles
or
- digital readout
CS 128/ES 228 - Lecture 10a
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Angles: readability
Horizontal & vertical
circles typically
graduated to 1o for
construction grade
instruments, 5’ or
better for survey
instruments
Vernier improves
resolution by 10x or
better
Principles of Surveying. 2nd ed. C. A. Herubin, 1978
Digital readouts to 5”
or better
CS 128/ES 228 - Lecture 10a
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Measuring a distance
Start with known location or
previous point
Three techniques:
1. Taping
2. Stadia markings
3. Electronic distance
measurements (EDM)
CS 128/ES 228 - Lecture 10a
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Taping: errors (& fixes)
Alignment – plumb bob
Tension – tension
handle (or experience)
Thermal expansion –
correction tables
Diagram: www.benmeadows.com
Slope - cosines
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Stadia markings + rod
stadia hairs
define a known
vertical angle
horiz. distance
= 100x vertical
less accurate
than taping but
faster
Both: Principles of Surveying. 2nd ed. C. A. Herubin, 1978
CS 128/ES 228 - Lecture 10a
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Electronic Distance Measurement
Optical: uses parallax.
Inexpensive but error
≥ 1%
Ultrasonic: mid-priced.
Accuracy ~ 0.1%
Laser: moderate to very
expensive. Accuracy 1
ppt or better
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Measuring elevations
Known as “leveling”
Uses a level (optical
or laser) & a rod
All measurements
are relative (to a
starting elevation)
Height of
instrument
Both: Elements of Surveying. U. S. Army, TM 5-232, 1971
CS 128/ES 228 - Lecture 10a
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Optical vs. laser leveling
Optical leveling requires
2 workers
Laser leveling can be
done alone, but easiest
when rod is equipped
with autodetector
(high/low/on signals)
Top: Principles of Surveying. 2nd ed. C. A. Herubin, 1978
Bottom: Topcon web site
CS 128/ES 228 - Lecture 10a
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Putting it together
Two ways of mapping
a region:
Traversing – used to
locate specific
features
Triangulation – used
to establish a
control network
over a region
Both: Elements of Surveying.
U. S. Army, TM 5-232, 1971
CS 128/ES 228 - Lecture 10a
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Types of traverses
Allowable “misclosure”
First order, Class I:
- 4 mm in 1 km
- 127 mm in 1000 km
Third order:
- 12 mm in 1 km
- 380 mm in 1000 km
Land surveys: ???
Both: Elements of Surveying.
U. S. Army, TM 5-232, 1971
CS 128/ES 228 - Lecture 10a
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The total station
Topcon web site
Combines theodolite,
EDM, data logger &
surveying software
Log ~ 8000 points,
download data to
computer
Why doesn’t ES have
one???
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