[ppt]land surveying - wando high school engineering:...
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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 NOAAhttp://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
Horizontal Plane
Plu
mb
Line
Rod
Geodetic Survey Line of equal elevation
Plane Survey Line of equal elevation
Geoid or other Datum
Geodetic vs. Plane Survey
Earth’s surface
Rod
Types of Surveys
• Control Survey• Topographic Survey• Property Survey• Site Survey• Construction Survey
Control SurveyEstablish precise horizontal and vertical positions of points that serve as a reference for other surveys
Courtesy Department of Public Works, Seminole County, FLPhotos Courtesy NOAA
Topographic Survey
Gathers data on the location of natural and man-made 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 SurveyLocates 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 surveysHorizontal Datum = Collection of points of known latitude and longitude
Vertical Datum = Collection of points of known elevation
Benchmark (BM) = Permanent mark that establishes a point of known elevation
Wikimedia.org
Courtesy NOAA http://oceanservice.noaa.gov/education/kits/geodesy/geo05_horizdatum.html
Reference System DataInformation on datum points available at http://www.ngs.noaa.gov/cgi-bin/datasheet.prl
Example Data Sheet
Optical EquipmentRequires a visual line-of-sight
A theodolite measures vertical and horizontal angles
A total station is an electronic/optical surveying instrument
©iStockphoto.com ©iStockphoto.com
Optical Equipment
Automatic (Auto) Level• Commonly used on
building sites• Internal compensator
can automatically level the instrument
• Measures difference in elevation between the line of sight and a point
Kennedy
Other Equipment
Courtesy USGS http://gallery.usgs.gov/photos/07_22_2009_j51Qi76Hgb_07_22_2009_13
TripodLeveling Rod
Professional Tape Measure©iStockphoto.com
Field Book
Kennedy
Kennedy
Kennedy
Kennedy
GPS TechnologyGlobal 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
©iStockphoto.com
Kennedy
Auto Level
Bulls Eye Level
Telescope
Leveling Screws
Horizontal Angle Rotation Ring
EyepieceHorizontal Tangent Knob
Sight
Diopter Adjustment Ring
Mirror
Kennedy
Reading the Rod
View through the telescope
Horizontal crosshair
Verticalcrosshair
Stadia hairs
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
Rod Reading = 5.06 ft
Lower Stadia = 4.99 ft
Upper Stadia = 5.13 ft
Read the Rod
Instrument
Point of Unknown Elevation
Differential Leveling
The establishment of differences in elevation between two or more points with respect to a datum
BM
RodRod
Differential Leveling
• Start with point of known elevation
Benchmark (BM)Point of Reference (POR)
Rod reading7.59 ft (BS)
7.59
ft
• Sight to rod on BMBacksight (BS)
• Height of Instrument (HI)HI = BM elev + BSHI = 350.00 + 7.59 = 357.59 ft
357.59 ft (HI)
357.
59 ft
Field Notes AUTO LEVEL READINGS
STADIA
PT(+)BS HI
(-)FS ELEV
TOP/BOT STADIA
DIST/Angle
BM 350.00
7.59 357.59 7.85 / 7.33 52 ft
Differential LevelingWithout moving the tripod,
• Sight to rod on point of unknown elevation
Foresight (FS)• Identify elevation of
point
Elev.355.23 ft
Rod reading2.36 ft (FS) 2.
36 f
t
Point of Interest
Elev = HI - FSElev = 357.59 – 2.36 = 355.23 ft
Field Notes
AUTO LEVEL READINGS
STADIA
PT(+)BS HI
(-)FS ELEV
TOP/BOT STADIA
DIST/Angle
BM 7.59 357.59 350.00 7.85 / 7.33 52 ft
xPT- A 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(+)BS HI
(-)FS ELEV
TOP/BOT STADIA
DIST/Angle
BM 7.59 357.59 350.00 7.85 / 7.33 52 ft
PT-A 2.36 355.23 2.54 / 2.19 35 ft
x
PT- B 4.17 353.42PT-C 12.91 344.68
4.40 / 3.93 47 ft
13.21 / 12.61 60 ft
Image SourcesSanford, 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