CE310 Week 2 Notes
CE310 Week 2 Notes CE 310
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This 3 page Class Notes was uploaded by Nicole carkin on Monday September 5, 2016. The Class Notes belongs to CE 310 at Pennsylvania State University taught by Brian Naberezny in Fall 2016. Since its upload, it has received 5 views. For similar materials see Surveying in Civil Engineering at Pennsylvania State University.
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Date Created: 09/05/16
CE 310: Surveying Week 2 Lecture and Lab notes Units and Sig. Figs. (significant figures) 5 Basic Types of Observations Distances and angles Magnitudes and their Units Quantities: Length, Angle, Area, Volume Units depend on which system you are using o English or Metric(SI) Length Standards Foot (English) or Meter (SI) US Survey Foot  o 1 m = 39.37 in International Survey Foot  o 1 in = 2.54 cm o 1 ft = 0.3048 m The two different versions create small discrepancies Problems It is impossible to convert everything from U.S. to International Each state chooses which to follow, so its different everywhere SOLUTION: Surveyors measure in decimal feet for conversions Before the Foot There was a Rod/Pole/Perch = 16.5 ft Gunters chain; metal; 100 links; 66 ft 1 mi = 80 chains = 5280 ft Vara 33 in Example to convert from feet to chains: chains units are given in chains and links 1132.86 ft * (1 chain / 66 feet) = 17.1645 chains now convert the decimal 0.1645 * (100 links/1 chain) = 16.445 links 17 chains 16.4 links the chain will be a whole number, use sig figs Area Standards SI: m , ha (hectare), km 2 2 ha = 10,000 m English: ft , yd , acre, arpent o Acre= 10 chains = 10*66 = 43,560 ft 2 o Arpent .85 acres Volume Standards SI: m 3 3 3 English: ft , yd , acrefoot Angle Standards SI: rad English: Written as: Degree Minutes’ Seconds” o Degree () = 1/360 of a circle = 60 min o 1 min (‘) = 60 sec (“) o Decimal degrees (ddd.dddd) will see these in lab o HP format (ddd.mmss) Example to convert to Degrees Minutes Seconds from 45.5069 45 Use the whole number as the degree 0.5069*60 = 30.404 30’ Take the decimal portion and convert to minutes 0.141*60=24.84 25” Take the decimal portion and convert to seconds 45 30’ 25” Accuracy and Precision Observations can be direct or indirect Direct – Measuring device can be applied directly Indirect – Value is determined by relationship of other observations Accuracy and the Number of Digits Sig figs Example: o Tape measure, graduated to 0.01 ft If you measure 1.15 ft that is three sig figs and the last is estimated Must use sig figs for accuracy o If you add that is false precision o Don’t waste time and drop sig figs Digits ≠ sig. figs. Problems with zeros and sig fig intent o Use notations or hachmarks Stick to the same precision o You can only be as precise as your least precise tool Addition/subtraction o Round to the left most decimal Multiplication/Division o Keep the same # of least sig figs involved Sig Figs in Surveying Field measure preformed to set precision o Used in calcs In computations carry out to one more Round final answer Conversions are exact o Use smallest involved not the conversion factors How to round o Odd with a 5 round up o Even ditch the 5 and stay Errors sources can be natural, instrumental, or personal o Natural: environment o Instrumental: construction or adjustment of instruments o Personal: limitations of human Systematic or random Discrepancy is the difference between two observations of the same quantity Small discrepancy: no mistakes, small random errors; may be systematic errors Large discrepancy: mistake or presence of systematic errors Accuracy ≠ Precision Precision: consistency or refinement of a group of observations o Small discrepancies >high precision, Large discrepancies > low precision Accuracy: absolute nearness of an observation to the true
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