CS 128/ES Lecture 10a1 Surveying

CS 128/ES Lecture 10a2 Data for a GIS Raster data - characteristics? - sources? Vector data - characteristics? - sources? Bottom: Elements of Surveying. U. S. Army, TM 5-232, 1971

CS 128/ES Lecture 10a3 History of surveying Babylon: knew triangle; developed base-60 system Egypt: used simple plumb line sighting & right-angle instruments. Great pyramid: base square to 0.2 m out of 230 (0.09%) Top: The Roman Land Surveyors. O. A. W. Dilke, 1971

CS 128/ES Lecture 10a4 The motive for surveying? The priests also said that this king divided the country among all the Egyptians, giving each an equal square plot. This was the source of his revenue, as he made them pay a fixed annual tax. If anyone’s land were taken away by the river, he came to the king and told him what had happened. Then the king sent men to look at the land and measure how much less it was, so that in future the owner would pay the due proportion. Herodotus, referring perhaps to Sesostris II of Egypt ( BC). From: Dilke. The Roman Land Surveyors. Barnes & Noble, NY

CS 128/ES Lecture 10a5 Two types of surveys Geodetic survey - covers distances large enough that curvature of Earth is significant - establishes network of precisely located control points Plane survey [not ‘plain’] - straight lines & angles are sufficient - what about long, linear features?

CS 128/ES Lecture 10a6 National Geodetic Survey Functions:  defines & manages the National Spatial Reference System  sets standards for geodetic surveys  maintains a database of U. S. geodetic markers

CS 128/ES Lecture 10a7 NGSurvey data sheets

CS 128/ES Lecture 10a8 Uses for plane surveys Land survey Engineering or construction surveys Field mapping Top: Plane Table Mapping. M. Denny. Bottom:

CS 128/ES Lecture 10a9 Basic methods Locating a point Measuring an angle Measuring a distance Measuring differences in elevation

CS 128/ES Lecture 10a10 Locating a point Start with known location or previous point Direction + distance common for plane surveys (ex. “metes & bounds”) Two angles common for geodesy Principles of Surveying. 2 nd ed. C. A. Herubin, 1978

CS 128/ES Lecture 10a11 Measuring an angle Horizontal angles: use level, transit, or theodolite Vertical angle: use transit or theodolite Either: - graduated circles or - digital readout Both: Principles of Surveying. 2nd ed. C. A. Herubin, 1978

CS 128/ES Lecture 10a12 Angles: readability Horizontal & vertical circles typically graduated to 1 o for construction grade instruments, 5’ or better for survey instruments Vernier improves resolution by 10x or better  Digital readouts to 5” or better Principles of Surveying. 2nd ed. C. A. Herubin, 1978

CS 128/ES Lecture 10a13 Measuring a distance Start with known location or previous point Three techniques: 1. Taping 2. Stadia markings 3. Electronic distance measurements (EDM)

CS 128/ES Lecture 10a14 Taping: errors (& fixes) Alignment – plumb bob Tension – tension handle (or experience) Thermal expansion – correction tables Slope - cosines Diagram:

CS 128/ES Lecture 10a15 Stadia markings + rod stadia hairs define a known vertical angle horiz. distance = 100x vertical less accurate than taping but faster Both: Principles of Surveying. 2nd ed. C. A. Herubin, 1978

CS 128/ES Lecture 10a16 Electronic Distance Measurement Optical: uses parallax. Inexpensive but error ≥ 1% Ultrasonic: mid-priced. Accuracy ~ 0.1% Laser: moderate to very expensive. Accuracy 1 ppt or better

CS 128/ES Lecture 10a17 Measuring elevations Known as “leveling” Uses a level (optical or laser) & a rod All measurements are relative (to a starting elevation) Height of instrument Both: Elements of Surveying. U. S. Army, TM 5-232, 1971

CS 128/ES Lecture 10a18 Optical vs. laser leveling Optical leveling requires 2 workers Laser leveling can be done alone, but easiest when rod is equipped with autodetector (high/low/on signals) Top: Principles of Surveying. 2nd ed. C. A. Herubin, 1978 Bottom: Topcon web site

CS 128/ES Lecture 10a19 Putting it together Two ways of mapping a region: Traversing – used to locate specific features Triangulation – used to establish a control network over a region Both: Elements of Surveying. U. S. Army, TM 5-232, 1971

CS 128/ES Lecture 10a20 Types of traverses Allowable “misclosure” First order, Class I: - 4 mm in 1 km mm in 1000 km Third order: - 12 mm in 1 km mm in 1000 km Land surveys: ??? Both: Elements of Surveying. U. S. Army, TM 5-232, 1971

CS 128/ES Lecture 10a21 The total station Combines theodolite, EDM, data logger & surveying software Log ~ 8000 points, download data to computer Why doesn’t ES have one??? Topcon web site