 # Surveying Defined What is surveying Surveying is the

• Slides: 30 Surveying Defined • What is surveying? Surveying is the art of measuring distances, angles and positions on or near the surface of the earth. • Why it is an art? Because only a surveyor who possesses through understanding of surveying techniques will be able to determine the most efficient methods required to obtain optimal results over a wide variety of surveying problems. • Why it is scientific? Because the use of mathematical techniques to analyze field data, accuracy and reliability depends on understanding scientific principles underlying and affecting survey measurement. Why should I study surveying? • You may be required to perform simple surveying operations (particularly if you're employed in construction company and Local Gov. ), or you will need to discuss your needs with surveyors. • Every Engineer needs surveying skills Categories of Surveying: Plane Surveying – surveying with the reference base for fieldwork and computations are assumed to be a flat horizontal surface. Generally within a 12 mile radius the pull of gravity is very nearly parallel to that at any other point within the radius and thus horizontal lines can be considered straight. Geodetic Surveying – surveying technique to determine relative positions of widely spaced points, lengths, and directions which require the consideration of the size and shape of the earth. (Takes the earth’s curvature into account. ) Geoid surface 12/18/2021 4 ° - ‘ - “ to Decimal Degrees n 32° 15’ 24” n n n 1 degree = 60 minutes 1 minute = 60 seconds 24” = 24/60’ = 0. 4’ 15’ 24” = 15. 4’ = 15. 4/60° = 0. 2567° 32° 15’ 24” = 32. 2567° Most calculators do trig calculations using decimal degrees - CONVERT! Geometry of a Circle 23° 18’ Total angle = 360° 4 quadrants - NE, SW, NW - each total 90° Angles typically measured East from North or East from South Clockwise (CW) and Counterclockwise (CCW) angles add to 360° NW NE SW SE 360° - 23° 18’ = 336° 42’ Geodde plan eleps 12/18/2021 7 BRANCHES OF SURVEYING 1 - Topographic survey: preliminary surveys used to tie earth surface features. 2 - Hydrographic survey: preliminary surveys tie underwater feature to surface control line 3 - Route surveys: preliminary, layout and control surveys that range over a narrow but long strip of land (highways, railroads, electricity transmission lines and channels). 4 - Property surveys: preliminary, layout and control surveys determine boundary locations for a new map. 5 - Aerial survey: preliminary and final surveys convert aerial photograph into scale map using photogram metric tech. 6 - Construction survey: layout of engineering work. 7 - Final (as built) survey: preliminary surveys tie in features that just have been constructed PHASES OF SURVEYING 1 - Field Work Data procurement phase 2 - Office Work: – • • • � data are Analyzed Reduced to useful form by mathematical calculations Adjusted Frequently converted to graphical mode of Expression 12/18/2021 10 Parts of Surveyor’s work: • Decision making (selecting techniques, equipments, etc. ) • Fieldwork (data acquisition) • Data processing (calculations to give locations, areas, volumes, etc. ) • Mapping (maps, plans, charts) • Reporting (conclusion of the task) 12/18/2021 11 Surveying Instrument 1 - Transit and theodolite: Establish straight or curved lines, horizontal and vertical angles. 2 - The level and rod: measure difference in elevations. 3 - Steel tape: measure horizontal and slope distances. 4 - Total station. 5 - GPS (global positioning system) receivers. Steel tape Level ( stadia principle ) Total station Thedilite GPS Errors - No measurement (except count) can be free of error. -True value is determined statistically (mean) to calculate error. Systematic error: error whose magnitude and algebraic sign can be determined and eliminated (temp. error). Random Error: - Error due to surveyor skill. - Tend to cancel each other. - Little significance except for high precision survey. - Unskilled or careless surveyor can make problem. - Large random error doesn’t result in accurate work even if they cancel. Mistakes There are many mistakes that cold be happened to surveyors. - Blunders made by survey personnel e. g. 68 instead of 86. - Miscounting tape length, measuring from wrong point. - Mistakes will occur and must be discovered and eliminated by verifying the measurement (Repeat Geometry analysis, etc. ). - Every measurement should be repeated to eliminate mistakes and improved precision. ACCURACY & PRECISION q Accuracy : closeness between measurement and "true” value. q Precision : closeness to one another of a set of repeated observations 12/18/2021 16 Direct and Indirect Measurement § Direct measurement § Applying a tape to a line § Applying a protractor to a line § Turning an angle with a transit § Indirect § Secured when direct measurement is not possible. Always will be in relation to some other measured quantity. Thus some knowledge of math functions are necessary Measuring Four kinds of measurements form the basis for all plane surveying Distance ◦ § Horizontal distance § Slop distance § Vertical distance � Angles • Horizontal angles • Vertical angles 12/18/2021 19 Horizontal angles Vertical angels 12/18/2021 20 Units of Measure Distance � Basic units are for length and � The Foot – King Edward I proclaimed that one inch was equal to three ◦ corns of barley laid end to end. The meter – Is defined as one wavelength of the element Krypton by an ◦ international committee that worked 19 years to come to consensus on October 1960. UNITS OF LENGTH qmperial units (feet): §Usually subdivided into decimal units in Surveying, use of inches. Defined 1 Yard = 0. 9144 meter (exact) § 1 ft = 0. 3048 m (exact) § 1 inch = 25. 4 mm (exact) §Did not change relationship established by Congress – kept for surveying and called U. S. Survey foot 12/18/2021 22 q. SI units (meters): §Le System International d’Unites (International System of Units §Normally subdivided into decimeter, centimeter, millimeter NORMAL PREFIXES FOR METER �� exa (E) 10^18 �� peta (p) 10^15 �� tera (t) 10^12 �� giga (g) 10^9 �� mega (m) 10^6 �� kilo (k) 10^3 �� hecto (h) 10^2 �� deka (da) 10^1 �� Ex: kilometer = 1, 000 m �� deci (d) 10^-1 �� centi (c) 10^-2 �� milli (m) 10^-3 �� micro (μ)10^-6 �� nana (n) 10^-9 �� pico (p) 10^-12 �� femto (f) 10^-15 �� atto (a) 10^-18 12/18/2021 �� Ex: millimeter = 0. 001 m 23 Unit measuring of angles Deg-Min-Sec 24 ° - ‘ - “ to Decimal Degrees n 32° 15’ 24” n n n 1 degree = 60 minutes 1 minute = 60 seconds 24” = 24/60’ = 0. 4’ 15’ 24” = 15. 4’ = 15. 4/60° = 0. 2567° 32° 15’ 24” = 32. 2567° Most calculators do trig calculations using decimal degrees - CONVERT! Geometry of a Circle 23° 18’ Total angle = 360° 4 quadrants - NE, SW, NW - each total 90° Angles typically measured East from North or East from South Clockwise (CW) and Counterclockwise (CCW) angles add to 360° NW NE SW SE 360° - 23° 18’ = 336° 42’    