Stadia markings rod n stadia hairs define a
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Stadia markings + rod n stadia hairs define a known vertical angle n horiz. distance = 100 x vertical n less accurate than taping but faster Both: Principles of Surveying. 2 nd ed. C. A. Herubin, 1978 CS 128/ES 228 - Lecture 10 a 1
Electronic Distance Measurement n Optical: uses parallax. Inexpensive but error ≥ 1% n Ultrasonic: mid-priced. Accuracy ~ 0. 1% n Laser: moderate to very expensive. Accuracy 1 ppt or better CS 128/ES 228 - Lecture 10 a 2
Measuring elevations n Known as “leveling” n Uses a level (optical or laser) & a rod n All measurements are relative (to a starting elevation) n Height of instrument Both: Elements of Surveying. U. S. Army, TM 5 -232, 1971 CS 128/ES 228 - Lecture 10 a 3
Optical vs. laser leveling n Optical leveling requires 2 workers n Laser leveling can be done alone, but easiest when rod is equipped with autodetector (high/low/on signals) Top: Principles of Surveying. 2 nd ed. C. A. Herubin, 1978 Bottom: Topcon web site CS 128/ES 228 - Lecture 10 a 4
Putting it together Two ways of mapping a region: n Traversing – used to locate specific features n Triangulation – used to establish a control network over a region Both: Elements of Surveying. U. S. Army, TM 5 -232, 1971 CS 128/ES 228 - Lecture 10 a 5
Types of traverses Allowable “misclosure” n First order, Class I: - 4 mm in 1 km - 127 mm in 1000 km n Third order: - 12 mm in 1 km - 380 mm in 1000 km n Land surveys: ? ? ? Both: Elements of Surveying. U. S. Army, TM 5 -232, 1971 CS 128/ES 228 - Lecture 10 a 6
The total station Topcon web site n Combines theodolite, EDM, data logger & surveying software n Log ~ 8000 points, download data to computer n Why doesn’t ES have one? ? ? CS 128/ES 228 - Lecture 10 a 7
