Transcript Surveying - St. Bonaventure University

Surveying
CS 128/ES 228 - Lecture 10a
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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
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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.
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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?
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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
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Basic methods

Locating a point

Measuring an angle

Measuring a distance

Measuring differences
in elevation
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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
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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
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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)
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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
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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
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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
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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
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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
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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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