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Distance MeasuringTwo principles of measuring distanceDistanceBest methodExampleBarbed WireWooden PoleFoundationHorizontal & Slope DistanceDifference Between Horizontal and Slope DistanceHorizontal DistanceSlope distanceDetermining Horizontal DistanceUsing Equipment To Measure Horizontal DistanceUsing Equipment To Measure Horizontal Distance--Stadia1/2 StadiaUsing Equipment To Measure Horizontal Distance--(EDM)Calculating Horizontal DistanceCalculating Horizontal Distance --Percent slopeCalculating Horizontal Distance--Difference in ElevationCalculating Horizontal Distance--Vertical AngleQuestions ?Distance MeasuringTwo principles of measuring distance1) It takes two points to form a line. 2) The shortest distance between two points is a straight line.DistanceIn surveying, the term “distance” has two uses. The common use is to measure the displacement (distance) between two or more points. Distance can also be used to define the dimensions of an objectBest methodDetermined by:EnvironmentUse of the dataEquipment availableExpertise of individualsPersonal preferenceTopographyClient specificationsRegulationsStandard practiceThe most important factor is the use of the data.ExampleWhat method should be used to determine the amount of materials needed to build a fence?Barbed WireBarbed wire is usually purchased in rolls that contain 100 rods of wire.Does the precision need to be 1/100’s of a foot? NoWooden PoleHorizontal poles are usually six to eight feet.Is pacing an acceptable method?YesFoundationMeasuring the location of forms for a foundation is a different job.Distances should be measured to 1/8 or 1/4 inch.Horizontal & Slope DistanceHorizontal distance is a distance measured on a horizontal plane.Horizontal distance can also be calculated.Slope distance is a distance measured on a surface that is not a plane.For general surveying the difference between horizontal and slope distance is ignored for slopes less than 5%.Difference Between Horizontal and Slope DistanceThe illustration shows the difference that occurs for a 3% slope.The actual difference in length is: € % Slope =riserun x 100Rise =% slope100 x run = 0.03 x 100 = 3 € a2= b2+c2 b = a2−c2 = 1002−32= 99.95When the slope is 3%, the difference between slope distance and horizontal distance is 0.05 feet per 100 feet.Horizontal DistanceTo measure horizontal distance, the tape must be on a horizontal plane.The earth surface is seldom a horizontal plane.Slope distanceWhen distance is measured on the surface of the ground it is called slope (surface) distance.Determining Horizontal Distance The surveyor has two choices.Use equipment and techniques to measure horizontal distance.Measure slope distance and collect additional information to calculate horizontal distance.Using Equipment To Measure Horizontal DistanceChain, level and plumb bob.Using Equipment To Measure Horizontal Distance--StadiaStadia distance is a horizontal distance because a level instrument is used to collect the data.1/2 StadiaUsing Equipment To Measure Horizontal Distance--(EDM)An EDM measures distance by determining the amount of time required for a signal to leave the instrument, reflect off of the target, or object, and return.If the instrument is level when the measurement is taken, the measurement is horizontal distance.Calculating Horizontal DistanceTo calculate horizontal distance you must know the slope distance and one additional bit of information for each station. Either:% slopeorChange in elevationorVertical angle.Calculating Horizontal Distance --Percent slope € % Slope =RiseRun x 100Rise =% Slope x Run100=2 x 255.30 ft100= 5.11 ft € a2= b2+c2b = a2−c2 = 255.302−5.112 = 255.25 ftCalculating Horizontal Distance--Difference in Elevation € a2= b2+c2b = a2−c2 = 234.52−6.52 = 234.41 ft€ Cosin θ =adjhypadj = Cosin θ x hyp= Cosin 19.2 x 510.17 ft= 0.9444 x 510.17= 481.79 ft Calculating Horizontal Distance--Vertical AngleQuestions

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