Transcript Land Surveying

Land Surveying
Definition of Surveying in the State of
Tennessee (T.C.A. 62-18-102)
Any service of work, the adequate performance of which
involves the application of special knowledge of the
principles of mathematics, the related physical and applied
sciences, and the relevant requirements of law for
adequate evidence to the act of measuring and locating
lines, angles, elevations, natural and man-made features
…for the purpose of determining areas and volumes, for
the monumenting of property boundaries, and for the
platting and layout of lands and subdivisions thereof,
including the topography, drainage, alignment and grades
of streets, and for the preparation and perpetuation of
maps, records, plats, field notes, records and property
descriptions that represent these surveys.
Famous Land Surveyors
• George Washington
Surveyor General in Virginia, 1749
• Thomas Jefferson
County Surveyor for Albemarle County, VA, 1773
• Lewis and Clark
Expedition to explore and survey the west
• Daniel Boone
Resolved Kentucky land disputes
• Abraham Lincoln
Surveyor in Illinois when elected to state
legislature
Land Surveying
The science of determining the relative
positions of points on the Earth’s surface.
– Geodetic Surveys
– Plane Surveys
Geodetic Survey
• Takes into account the true size, shape, and
gravity fields of the Earth
– The geoid is the equipotential surface of the
Earth’s gravity field which best fits global mean sea
level
• Provides significant
precision
• Establishes highly
accurate control
networks
Images courtesy NOAA
http://celebrating200years.noaa.gov/foundations/gravity_surveys/
Plane Survey
• Assumes the Earth’s surface to be a plane (flat)
• More common than geodetic surveys
• Precise enough for small-scale surveys in a
limited area, such as a construction site
• Used to determine legal boundaries,
construction surveys, and small-area
topographic or control surveys
©iStockphoto.com
Geodetic Survey
Line of equal elevation
Plumb Line
Geodetic vs. Plane Survey
Rod
Plane Survey
Line of equal elevation
Rod
Horizontal Plane
Earth’s surface
Geoid or other Datum
Types of Surveys
•
•
•
•
•
Control Survey
Topographic Survey
Property Survey
Site Survey
Construction Survey
Control Survey
Establish precise
horizontal and
vertical positions of
points that serve as
a reference for other
surveys
Photos Courtesy NOAA
Courtesy Department of Public Works, Seminole County, FL
Topographic Survey
Gathers data on the location of natural and manmade features, contours, and ground elevation
to create a topographic map
Courtesy USGS
Property Survey
(or Boundary Survey)
• Establishes property
lines for a lot
• Used to create a plat
Site Survey
(Plot Survey or Lot Survey)
• Combination of a property survey and
topographic survey
• May be required to receive a construction permit
Construction Survey
Locates points and elevations that can be
used to establish correct locations and
elevations for engineering and
architectural projects
Courtesy Isle of Palms, SC Recreation Department
National Spatial Reference
System (NSRS)
Common set of reference points for all
surveys
Horizontal Datum = Collection of
points of known latitude and longitude
Vertical Datum = Collection of points
of known elevation
Courtesy NOAA
http://oceanservice.noaa.gov/education/kits/geod
esy/geo05_horizdatum.html
Benchmark (BM) = Permanent mark
that establishes a point of known
elevation
Wikimedia.org
Reference System Data
Information on datum points available at
http://www.ngs.noaa.gov/cgibin/datasheet.prl
Example Data Sheet
Optical Equipment
Requires a visual line-of-sight
©iStockphoto.com
A theodolite measures
vertical and horizontal
angles
©iStockphoto.co
m
A total station is an
electronic/optical
surveying instrument
Optical Equipment
Automatic (Auto) Level
• Commonly used on
building sites
• Internal compensator
can automatically
level the instrument
Kennedy
• Measures difference in elevation between
the line of sight and a point
Kennedy
Other Equipment
©iStockphoto.com
Professional Tape Measure
Kennedy
Kennedy
Leveling Rod
Courtesy USGS
http://gallery.usgs.gov/photos/07_22_20
09_j51Qi76Hgb_07_22_2009_13
Tripod
Kennedy
Field Book
GPS Technology
Global Positioning System
• A global navigation satellite
system
• Developed by the U.S.
Department of Defense
• A constellation of satellites that
broadcast radio signals
• Receivers intercept several
satellite signals in order to
determine precise location
Courtesy NASA
Widimedia.com
GPS
Kennedy
©iStockphoto.com
Telescope
Auto Level
Sight
Mirror
Diopter
Adjustment
Ring
Bulls Eye
Level
Horizontal
Tangent
Knob
Horizontal
Angle
Rotation Ring
Eyepiece
Leveling
Screws
Kennedy
Reading the Rod
Vertical
crosshair
Stadia hairs
Horizontal
crosshair
View through the telescope
Beveled
hatch
marks
Reading the Rod
Upper Stadia Reading = 5.30 ft
Rod Reading = 5.25 ft
Lower Stadia Reading = 5.20 ft
Stadia Readings
• Estimate distance between rod
and instrument
• Rod intercept is the difference
between stadia readings
• Estimated distance
• Stadia multiplier typically = 100
– Indicated on inside of instrument
case or in Instructional Manual
Stadia Readings
Upper Stadia Reading = 5.30 ft
Lower Stadia Reading = 5.20 ft
Rod Intercept = 0.10 ft
Stadia Reading
Upper Stadia = 5.13 ft
Rod Reading = 5.06 ft
Lower Stadia = 4.99 ft
Read the Rod
Differential Leveling
The establishment of differences in
elevation between two or more points with
respect to a datum
Instrument
Rod
Rod
BM
Point of
Unknown
Elevation
Differential Leveling
• Start with point of
known elevation
• Sight to rod on BM
Backsight (BS)
• Height of Instrument (HI)
HI = BM elev + BS
HI = 350.00 + 7.59 = 357.59 ft
357.59 ft
357.59 ft (HI)
7.59 ft
Benchmark (BM)
Point of Reference
(POR)
Rod reading
7.59 ft (BS)
Field Notes
AUTO LEVEL READINGS
STADIA
PT
BM
(+)
BS
HI
7.59
357.59
(-)
FS
ELEV
TOP/BOT
STADIA
DIST
/Angle
350.00
7.85 / 7.33
52 ft
Without moving the
tripod,
• Sight to rod on point
of unknown
elevation
Foresight (FS)
Rod reading
2.36 ft (FS)
• Identify elevation of
point
Elev = HI - FS
Elev = 357.59 – 2.36 = 355.23 ft
2.36 ft
Differential Leveling
Elev.
355.23 ft
Point of Interest
Field Notes
AUTO LEVEL READINGS
STADIA
PT
BM
PT- A
(+)
BS
7.59
HI
(-)
FS
ELEV
TOP/BOT
STADIA
DIST
/Angle
357.59
x
350.00
7.85 / 7.33
52 ft
2.36
355.23
2.54 / 2.19
35 ft
Differential Leveling
2.36 ft (FS)
7.59 ft (BS)
Differential Leveling
Elev. 350.00 ft
Field Notes
AUTO LEVEL READINGS
STADIA
PT
BM
(+)
BS
7.59
HI
(-)
FS
357.59
x
ELEV
TOP/BOT
STADIA
DIST
/Angle
350.00
7.85 / 7.33
52 ft
35 ft
PT-A
2.36
355.23
2.54 / 2.19
PT- B
4.17
353.42
4.40 / 3.93
47 ft
PT-C
12.91
344.68
13.21 / 12.61
60 ft
Image Sources
Sanford, F. (2006). Seminole County geodetic control
points. Seminole County, Florida: Department of Public
Works.
United States Geological Survey (USGS)
National Oceanographic and Atmospheric Administration
Photo Library
http://www.photolib.noaa.gov/cgs/marks1.html
Istockphoto.com