Civil Engineering Surveying Roy Frank

Planning A Survey  Planning requires a well rounded understanding of surveying practices  Process: 1. Choice of accuracy required (depends on use to be made) 1. Basic Control 2. Topographic 3. Photogrammetry

Planning A Survey 2.Existing Control 1.Search records for existing control in area 1.Illinois Geological Survey – Urbana, IL 2.National Geodetic Survey – Rolla, MO or Rockville, Maryland 3.Reconnaissance: 1.Search Procedure: 1.Description often dated 2.Can use GPS receiver (Lat. And Long) 3.Probe, detectors – often problems - brass

Planning A Survey 4.Choice of Instruments and Methods 1.Depends on availability, location, existing features, and accuracy 5.Computation and Drafting

Accuracy and Errors  Accuracy depends on: 1.Precise instruments 2.Precise Methods 3.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 1.Blunders 2.Systematic Error 3.Accidental Error  Blunder is a mistake, to help eliminate: 1.Every value to be recorded must be checked by some independent field observation

Errors 2. Once check indicates that there is no blunder, field record must never be changed or destroyed 3. 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: 1.All surveying equipment must be designed and used so that whenever possible systematic errors will be eliminated automatically 2.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 1. Surveys and mapping of bodies of water and shorelines 2.Rivers and Lakes – Process different 2.Rivers 2.Normal process is to establish 2 parallel lines of control points on opposite sides 3.River Portion: 2 processes 2.EDM similar to radial 3.Dual instrument with position by angle and intersection 3.Lakes 2.Normal process same as river but generally do not have current problems

Overall Process: 1. Establish control points both horizontal and vertical 2. Preplan where sections are to be taken (this is basis for control points on shore) 3. Cross sections taken 4. If EDM, radials taken from control points due to difficulty in obtaining shots under 300’ 5. 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: 1. Establish system of BM’s throughout area gauges will be installed 2. Establish elevation mark at site for installation 3. After gauges are installed, check elevation of each

Topographic Surveys  6 Basic Methods 1. Radial 2.Plus/Offset 2.Plus Offset 2.Establish baseline (Often centerline), establish points at station interval 50’, 100’, 200’ 3.Tie planimetric data by distance down line plus distance right or left (looking up stationing) 4.Establish elevations on station points then elevation out a predetermined distance with shots at breaks

Topographic Surveys 4.Due additional section to locate features in between stations 5.Equipment: Tape, Level, Rod, Transit, - Right Angle Prism? 2.Grid Method 1.Take cross Section Groups and Combine 2.Establish Grid baseline – often property line 3.Establish Perpendicular line 4.Both Marked at grid interval (25’, 50’) 5.Planimetric tied plus/offset in each grid 6.Grid laid out by double taping 7.Field notes 1 – 2 grids/page

Topographic Surveys 3.Photogrammetry 1.Limitations 1.Trees – Leaves off – no large growths of coniferous 2.Ground Cover – grass, thick weeds and vines, snow 3.Clear Sky 4.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 4.GPS: Total Station System 1.Basic of GPS 1.Topo with GPS 2.Topo: Trimble Total Station (RTK) 2.Limitations: 1.Must be able to maintain satellite signal – Trees, Building 2.Signal Reflection (Multipath) – Buildings, Fences, Roofs 3.Debate over elevation (0.15’ +/- my belief)

Topographic Surveys 5.Trace Contour 1.Used to identify several contours around an area 6.Plane Table Surveys 1.Rarely used 2.Method prepares a manuscript map in the field

Mapping and Map Drafting  2 Basic Types of Maps used in Engineering 1.Line Drawing 2.Photogrametrically prepared manuscript or orthophoto map

Mapping and Map Drafting 1.Datum in Mapping:  Datum used to correlate measurements, to determine elevations and horizontal positions for points at different locations  Topographic Maps using Symbols Show: 1.Spatial configuration of Earths surface (contours) 2.Natural Features (Lakes, Rivers, etc.) 3.Physical Changes caused by man

Mapping and Map Drafting 2.Planning Maps  Used in planning Engineering work or overall planning at the urban, Regional, or National Levels 3.Plotting Contours:  Interpolation: 1.Estimation 2.Computation

Mapping and Map Drafting 4.Contours  Characteristics of Contours: 1.Horizontal distance between contour lines is inversely proportionate to the slope 2.Uniform slopes have contours evenly spaced 3.Along plane surfaces (manmade) contour lines are straight and parallel 4.Contour lines are perpendicular to lines of steepest slope 5.All contours close upon themselves 6.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 1.Clarity with which features can be shown 2.Cost (larger scale – higher cost) 3.Correlation of Map data with related maps 4.Desired size of map sheet 5.Physical factors (number and character), nature of terrain, required contour interval

Mapping and Map Drafting 5.Map Classifications  Based on American Society of Civil Engineering, Surveying, and Mapping Division 1.Design Maps:  Used to design and construct 6.Information shown on Maps: