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Land survey
- 2. LAND SURVEY PRESENTED BY: Hashim Ullah Wazir (Group leader) 2016-QUD-F-67 • M. Salman Khan 2016-QUD-F-84 • Haris Shah 2016-QUD-F-60 • Umar Ullah Khan 2016-QUD-F-82 • Muhammad Bilal 2016-QUD-F-57 • Syed Abdullah Shah 2016-QUD-F-89 • Mohsin Khayal 2016-QUD-F-73
- 3. TO PRESENT • Definition of surveying • Famous land surveyors • Land surveying • Types of land survey • Equipments used in survey
- 4. Definition of Surveying in the State of Tennessee (T.C.A. 62-18-102) Any service of work, the performance which involves the application of special knowledge of measuring and locating lines, angles, elevations, natural and man-made features …for the purpose of determining areas and volumes, for the property boundaries, and for the platting and layout of lands and subdivisions also include the topography, drainage, alignment and grades of streets, and for the preparation of maps, records, plats, field notes, records and property descriptions that represent these surveys.
- 5. 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
- 6. Land Surveying The science of determining the relative positions of points on the Earth’s surface. –Geodetic Surveys –Plane Surveys
- 7. 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/
- 8. 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
- 9. Horizontal Plane PlumbLine 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
- 10. Types of Surveys • Control Survey • Topographic Survey • Property Survey • Site Survey • Construction Survey
- 11. Control Survey Establish precise horizontal and vertical positions of points that serve as a reference for other surveys Courtesy Department of Public Works, Seminole County, FL Photos Courtesy NOAA
- 12. Topographic Survey Gathers data on the location of natural and man- made features, contours, and ground elevation to create a topographic map Courtesy USGS
- 13. Property Survey (or Boundary Survey) • Establishes property lines for a lot • Used to create a plat
- 14. Site Survey (Plot Survey or Lot Survey) • Combination of a property survey and topographic survey • May be required to receive a construction permit
- 15. 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
- 16. 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 Benchmark (BM) = Permanent mark that establishes a point of known elevation Wikimedia.org Courtesy NOAA http://oceanservice.noaa.gov/education/kits/geod esy/geo05_horizdatum.html
- 17. Optical Equipment Requires a visual line-of-sight A theodolite measures vertical and horizontal angles A total station is an electronic/optical surveying instrument ©iStockphoto.com ©iStockphoto.co m
- 18. 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
- 19. Auto Level Bulls Eye Level Telescope Leveling Screws Horizontal Angle Rotation Ring Eyepiece Horizontal Tangent Knob Sight Diopter Adjustment Ring Mirror Kennedy
- 20. Other Equipment Courtesy USGS http://gallery.usgs.gov/photos/07_22_20 09_j51Qi76Hgb_07_22_2009_13 TripodLeveling Rod Professional Tape Measure ©iStockphoto.com Field Book Kennedy Kennedy Kennedy Kennedy
- 21. 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
Editor's Notes
- There are two categories of land surveys that require different surveying methods – geodetic surveys and plane surveys.
- A geodetic survey is based on the true shape of the Earth. The true shape of the Earth is not a sphere but an irregular ellipsoid shape. Many models of the true shape of the Earth exist. One model, the geoid, is a model of the assumed mean sea level which is dependent on the gravitational forces around the world. The western hemisphere geoid is shown in the computer-generated model on the left. The yellow and orange areas are further from the center of the Earth than the blue areas. Geodetic surveys use the geoid or another similarly shaped model as a basis. These surveys are performed with great precision and are used to establish highly accurate control networks that provide points of known position throughout the US and the world.
- In a geodetic survey, the geoid is taken as the datum. Lines that indicate level surfaces undulate with the strength of the gravitational field. In a plane survey, the curvature the Earth is considered flat, and lines of equal elevation are assumed to be horizontal planes. In this class, we will perform plane surveys.
- Control surveys are used to establish the latitude, longitude, and/or elevation of reference points that can be used for other types of surveys. The image here is published in the Seminole County Geodetic Control Points document (2006), which provides a description of the location of each control point in addition to the latitude, longitude, and/or elevation. These control points can then be used as a basis for topographic, construction, or other surveys. The photos show survey crew members setting survey marks during control surveys in Alaska. The black and white image was taken near White Pass, Alaska in 1936. The color photo is a more recent shot of a crew member mixing cement to set a mark in a rock in Southeast Alaska.
- This is an example of a topographic map for the area surrounding Stowe, Vermont. The contour lines indicate lines of constant elevation.
- This is an example of a recorded plat created from a property survey near Mount Pleasant, SC. The property lines are located using a length and a bearing angle.
- This site plan shows both property lines and contours from a topographic survey.
- Examples of construction surveys include staking a line and grade for a foundation, a fence, or a road. In the picture, the string lines were laid out based on a construction survey. Notice the surveying equipment to the right in the picture used to ensure that the foundations are poured to the correct elevation.
- The top photograph is an example of a horizontal datum marker. The bottom photo shows a benchmark.
- A level measures vertical differences in elevation. A theodolite measures vertical and horizontal angles. A total station is an electronic/optical instrument that combines a theodolite and an electronic distance meter (EDM) to measure distances.
- An automatic or auto level is commonly used on building sites because it is easy to set up and use.
- Before using the Auto level, the instrument should be leveled so that when the instrument is rotated, the line of sight defines a horizontal plane. The leveling screws allow the surveyor to adjust the alignment of the instrument to provide a horizontal line of sight. If properly calibrated, the instrument will be level when the bubble in the bulls eye level is within the circle. The mirror will reflect the bulls eye level when viewing from the eyepiece height. The sight can be used to roughly align the telescope with the rod position. Rotation of the horizontal tangent knob results in a fine horizontal adjustment. When looking through the telescope, it will slowly adjust the view left to right. The horizontal rotation ring is used to approximate horizontal angles. Rotating the diopter adjustment ring, which surrounds the eyepiece, can sharpen the crosshairs when viewed through the eyepiece.
- Other equipment often used in conventional optical surveys are a leveling rod, a tripod, a professional tape measure, and a field book. The tripod supports the surveying instrument. The tape is used to measure distances. The leveling rod is used to measure vertical distances with optical equipment and looks like an extra long measuring stick. The field book is used to record the measurements and observations taken during a survey.
- The GPS system can be used for surveying as well as navigation. The GPS system is a free-to-access system developed by the US Department of Defense. It consists of a constellation of many satellites that orbit the Earth, each broadcasting a unique radio signal. GPS receivers determine the distance to each satellite based on the time it takes the signal to reach the receiver. The location of the receiver on Earth can be determined from as few as three satellite signals. Multiple satellites are always accessible from any point on Earth at any time. The top picture is a NASA image of one of the GPS satellites. The bottom image shows a moment in time when a GPS receiver on Earth has access to 12 satellite signals. As the satellites orbit and the Earth spins, the number of visible satellites from a location changes.
- Some recreational GPS navigation units only calculate horizontal position (latitude and longitude) and superimpose the location on a map image. These units do not need a high degree of accuracy and may calculate location to within a few meters – close enough to determine which road you are on. Other handheld GPS receivers, like the one pictured here on the right, provide both horizontal and vertical position in terms of latitude, longitude, and elevation. The accuracy varies with the unit. Professional grade GPS surveying equipment, like that shown in the left image, provides a much higher level of accuracy than the lower cost recreational units. It calculates both horizontal and vertical position to a high degree of accuracy. This surveyor is setting up GPS surveying equipment which includes an antenna, a GPS receiver, and a remote receiver.