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Understand key steps in survey planning - from control and reconnaissance to computations and errors. Explore tools like GPS, theodolites, and photogrammetry. Learn techniques for hydrographic and topographic surveys. Discover essential rules and methods for accurate data collection.
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Civil Engineering Surveying Roy Frank
Planning A Survey • Planning requires a well rounded understanding of surveying practices • Process: • Choice of accuracy required (depends on use to be made) • Basic Control • Topographic • Photogrammetry
Planning A Survey • Existing Control • Search records for existing control in area • Illinois Geological Survey – Urbana, IL • National Geodetic Survey – Rolla, MO or Rockville, Maryland • Reconnaissance: • Search Procedure: • Description often dated • Can use GPS receiver (Lat. And Long) • Probe, detectors – often problems - brass
Planning A Survey • Choice of Instruments and Methods • Depends on availability, location, existing features, and accuracy • Computation and Drafting
Accuracy and Errors • Accuracy depends on: • Precise instruments • Precise Methods • Good Planning • Example: Angle turned with theodolite, pointed with care; readings checked thus good precision. Angle’s of 2-3” expected, real results angle’s 15” = accuracy
Errors • 3 Types • Blunders • Systematic Error • Accidental Error • Blunder is a mistake, to help eliminate: • Every value to be recorded must be checked by some independent field observation
Errors • Once check indicates that there is no blunder, field record must never be changed or destroyed • An overall check must be applied to every control survey. Make as many overall checks as possible.
Errors • Systematic Error – an error that under the same conditions will always be of same size and sign. • Basic Rules to Eliminate: • All surveying equipment must be designed and used so that whenever possible systematic errors will be eliminated automatically • Systematic error which can not be eliminated must be evaluated and their relationship to conditions that cause them must be determined. • Example: Temperature Corrections
Errors • Accidental Errors – (random errors) represent the limit of precision in the determination of a value • Corrected be laws of probability • Compass Rule and Least Squares
Hydrographic Surveys • Surveys and mapping of bodies of water and shorelines • Rivers and Lakes – Process different • Rivers • Normal process is to establish 2 parallel lines of control points on opposite sides • River Portion: 2 processes • EDM similar to radial • Dual instrument with position by angle and intersection • Lakes • Normal process same as river but generally do not have current problems
Overall Process: • Establish control points both horizontal and vertical • Preplan where sections are to be taken (this is basis for control points on shore) • Cross sections taken • If EDM, radials taken from control points due to difficulty in obtaining shots under 300’ • May have to combine cross sections and radial location to pick up anomalies not covered by cross sections
Gauging Stations • Purpose is to install either manually read or automatic gauges to determine stream, river, lake, or ocean elevations • Process: • Establish system of BM’s throughout area gauges will be installed • Establish elevation mark at site for installation • After gauges are installed, check elevation of each
Topographic Surveys • 6 Basic Methods • Radial • Plus/Offset • Plus Offset • Establish baseline (Often centerline), establish points at station interval 50’, 100’, 200’ • Tie planimetric data by distance down line plus distance right or left (looking up stationing) • Establish elevations on station points then elevation out a predetermined distance with shots at breaks
Topographic Surveys • Due additional section to locate features in between stations • Equipment: Tape, Level, Rod, Transit, - Right Angle Prism? • Grid Method • Take cross Section Groups and Combine • Establish Grid baseline – often property line • Establish Perpendicular line • Both Marked at grid interval (25’, 50’) • Planimetric tied plus/offset in each grid • Grid laid out by double taping • Field notes 1 – 2 grids/page
Topographic Surveys • Photogrammetry • Limitations • Trees – Leaves off – no large growths of coniferous • Ground Cover – grass, thick weeds and vines, snow • Clear Sky • Tall Buildings • Due to these Limitations Illinois only has on the average of 2 weeks flying time
Topographic Surveys • Scale – Photo • S = (f/H’) • Coordinates From Photos • XA = (xa/f)(H-ha) • YA = (ya/f)(H-ha) • Height of an object • r = radial dist. to top • d = radial dist. to top – radial dist. to bottom • h= d (H’) / r
Topographic Surveys • GPS: Total Station System • Basic of GPS • Topo with GPS • Topo: Trimble Total Station (RTK) • Limitations: • Must be able to maintain satellite signal – Trees, Building • Signal Reflection (Multipath) – Buildings, Fences, Roofs • Debate over elevation (0.15’ +/- my belief)
Topographic Surveys • Trace Contour • Used to identify several contours around an area • Plane Table Surveys • Rarely used • Method prepares a manuscript map in the field
Mapping and Map Drafting • 2 Basic Types of Maps used in Engineering • Line Drawing • Photogrametrically prepared manuscript or orthophoto map
Mapping and Map Drafting • Datum in Mapping: • Datum used to correlate measurements, to determine elevations and horizontal positions for points at different locations • Topographic Maps using Symbols Show: • Spatial configuration of Earths surface (contours) • Natural Features (Lakes, Rivers, etc.) • Physical Changes caused by man
Mapping and Map Drafting • Planning Maps • Used in planning Engineering work or overall planning at the urban, Regional, or National Levels • Plotting Contours: • Interpolation: • Estimation • Computation
Mapping and Map Drafting • Contours • Characteristics of Contours: • Horizontal distance between contour lines is inversely proportionate to the slope • Uniform slopes have contours evenly spaced • Along plane surfaces (manmade) contour lines are straight and parallel • Contour lines are perpendicular to lines of steepest slope • All contours close upon themselves • Different contours do not merge or cross one another (except vertical walls, overhangs, cliffs) on map
Mapping and Map Drafting • Factors that influence choice of map scale • Clarity with which features can be shown • Cost (larger scale – higher cost) • Correlation of Map data with related maps • Desired size of map sheet • Physical factors (number and character), nature of terrain, required contour interval
Mapping and Map Drafting • Map Classifications • Based on American Society of Civil Engineering, Surveying, and Mapping Division • Design Maps: • Used to design and construct • Information shown on Maps:
Mapping and Map Drafting • The following should be on a map: • Direction of Meridian (North) • Graphical Scale (Bar in case of reduction) • Legend or key of symbols • Title Block (identifiers) • Contour Interval • Datum to which both Horizontal and Vertical are Referenced • If coordinate base used – what system
Mapping and Map Drafting • If map is to become public record (subdivision). It must contain in addition to the above: • Length of each line • Direction of each line (bearing or angles) • Subdivision numbering system (lot and block) • Location and Kind of monuments • Names of property owners (on site and adjacent) • Full description of Boundary • Certificate of Surveyor that map is correct
Planning and Estimating from Topo Maps • Purpose of Topo maps • Profiles • Grade contour • Drainage Area • Limits determined by following characteristics: • Begins and ends at the point in the stream to which it applies • Passes through every saddle that divides drainage area • Often follows ridges • Reservoir Capacity
Earthwork Computations by Average End Area Prepare Cross Sections Differentiate between existing & proposed Planimeter Cross Sections Amount of cut & fill for each cross section Beginning and end stations have 0 value Compute Volume Conversion Constant: 1.852 = (100/27)/ 2 = {(Sta. Dist.)/ [CF/CY]} / 2
Earthwork by Average End Area • EARTHWORK BY AVERAGE END AREA (EXAMPLE) • END AREAS: STATION CUT EMBANKMENT 0+00 0 0 1+00 10 156 2+60 50 795 3+00 197 1526 4+80 5 110 5+00 0 0
SAMPLE END AREA STATION SUM SUM CUT FILL CUT FILL D/100 CUT FILL CUT FILL 0+00 0 0 10 156 1.0 10 156 10 156 1+00 10 156 60 951 1.6 96 1522 106 1678 2+60 50 795 247 2321 0.4 99 929 205 2607 3+00 197 1526 202 1636 1.8 364 2945 569 5552 4+80 5 110 5 110 0.2 1 22 570 5574 CUT: 570 X 1.852 = 1056 Cubic Yards EMBANKMENT: 5574 X 1.852 = 10324 Cubic Yards Compaction Factor = 25%, 10324 CY X 1.25 = 12905 CY Fill
U.S. Rectangular System • “IDEAL” Process: • Area divided by establishment of Principal Meridians and Baselines • Area divided into 24 mile square tracts quadrangle using guide meridians and Standards of Parallel (correction lines) • Divide 24 mile² tracts into 16 townships each 6 miles square • Divide townships into 36 one mile square sections
U.S. Rectangular System • “IDEAL” Process: • Area divided by establishment of Principal Meridians and Baselines • Area divided into 24 mile square tracts quadrangle using guide meridians and Standards of Parallel (correction lines) • Divide 24 mile² tracts into 16 townships each 6 miles square • Divide townships into 36 one mile square sections
Easements • Easement is a Legal document which allows someone to do something to and or through your property • Types: • Access (ingress/egress) • Construction • Water rights • Utility
Easement must Describe • What it is for (purpose) • Who between Must be signed by all who’s name appears on deed • Width of easement • Duration – specified number of years or perpetual or life • Description of where located Based on Rectangular system unless subdivision
Description Method for Waterline Easements • A strip 30 feet wide over, under, and across the _____ side of the _____ ¼ of the _____¼ of Section, ___, T__ __, R__ __of the ___ P.M., __________ County, Illinois said strip lying ______ of and adjacent to the _______ right of way line of the existing public road.
Global Positioning System(GPS) • Worldwide system of navigation satellites by U.S. Department of Defense • Started in 1982 • Civil GPS Service (CGS) • Views civil users in 3 groups: • Professional • Commercial • Recreational
Global Positioning System(GPS) • Provides info in 4 categories: • Planning information • Current status information • Historical information • Responses to user questions
Global Positioning System(GPS) • Information may be obtained from: • DOT/RSPA ATTN DMA 26 Room 8405 Washington, DC 20590 • Commandant USCG Headquarters G-NRN-2 2100 2nd Street SW Washington, DC 20593
Global Positioning System(GPS) • Information may be obtained from: • National Geodetic Survey NOAA; N/CG 142 Rockwall 306 Rockville, Maryland 20852
Global Positioning System(GPS) • Satellites broadcast on 2 bands • L1 modulated with P code (Precise Positioning Service – PPS) • L2 modulated with C/A code (Standard Positioning Service – SPS) • C/A mode intended for general use and capable of providing single point positioning • P mode is much more accurate but is reserved for military and government use
Global Positioning System(GPS) • Planning GPS Surveys – as important as the sophisticated needed to collect the data • Planning Phases: Presurvey reconnaissance; 2 stations site requirements; 3 connections to existing geodetic control; 4 network design; 5 satellite availability; 6 observing schedule
Global Positioning System(GPS) • Reconnaissance (presurvey) • Important to minimize delays or changes in observing schedule • Office planning • Obtain station descriptions • Prepare control diagrams • Preliminary Reconnaissance • Determine recoverability of existing control stations • Provide sketch showing existing and proposed stations • Suitability of existing stations for use by GPS
Global Positioning System(GPS) • Station site Selection (critical factors) • Obstructions with elevations greater than 15º-20º above horizontal should be avoided • Station mark must be suitable for occupation by tripod
Global Positioning System(GPS) • Networks Design • Design depends on • Surveys order and purpose • Number of receivers available • Desired spacing between stations • It is best to connect at least 3 existing geodetic control stations
Global Positioning System(GPS) • Field Operations • Survey team structure – determined totally by operation method • Numbers depends on: • Number of receivers • Number and length of observation stations • Time spent transporting equipment • Logistics and administrative needs
Global Positioning System(GPS) • Transportation • Monumentation • Power supply • Weather
Global Positioning System(GPS) • Total Process: • Establish receivers and have all track simultaneously • Data cleaned – search for ambiguities in data to identify correct integer values • All vector solutions are computed • 2-3 are accomplished by built in receiver computer • Data given by longitude and latitude
New System: NAVSTAR • L2C – civil signal – added to L2 with P code • Block II RM Satellites – Launch 2005-2009 • L5 – New Frequency – more powerful and larger bandwidth • Provides easier signal acquisition and tracking • Block IIF Satellites • Functional in mid 2013
GPS Field Data Collection Techniques • Static – minimum 3 receivers • Occupation/session 1-3 hours • PDOP < 6 with 4 satellites • Occupy 3 stations then move 2, leap frog techniques • Pseudo Static – can work with 2 receivers • Occupy for 2-5 minutes, each station must be occupied twice approximately 2 hours apart • Can loose satellite lock for short periods • PDOP < 5 with 4 satellites