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Distance Measuring

Distance Measuring. Two principles of measuring distance. 1) It takes two points to form a line. 2) The shortest distance between two points is a straight line. . Distance. In surveying, the term “distance” has two uses.

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Distance Measuring

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  1. Distance Measuring

  2. Two principles of measuring distance 1) It takes two points to form a line. 2) The shortest distance between two points is a straight line.

  3. Distance • In 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 object

  4. Best method • Determined by: • Environment • Use of the data • Equipment available • Expertise of individuals • Personal preference • Topography • Client specifications • Regulations • Standard practice The most important factor is the use of the data.

  5. Example • What method should be used to determine the amount of materials needed to build a fence?

  6. Barbed Wire • Barbed wire is usually purchased in rolls that contain 100 rods of wire. • Does the precision need to be 1/100’s of a foot? • No

  7. Wooden Pole • Horizontal poles are usually six to eight feet. • Is pacing an acceptable method? • Yes

  8. Foundation • Measuring the location of forms for a foundation is a different job. • Distances should be measured to 1/8 or 1/4 inch.

  9. Horizontal & Slope Distance • Horizontal 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%.

  10. Difference Between Horizontal and Slope Distance • The illustration shows the difference that occurs for a 3% slope. • The actual difference in length is: When the slope is 3%, the difference between slope distance and horizontal distance is 0.05 feet per 100 feet.

  11. Horizontal Distance • To measure horizontal distance, the tape must be on a horizontal plane. • The earth surface is seldom a horizontal plane.

  12. Slope distance When distance is measured on the surface of the ground it is called slope (surface) distance.

  13. 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.

  14. Using Equipment To Measure Horizontal Distance • Chain, level and plumb bob.

  15. Using Equipment To Measure Horizontal Distance--Stadia Stadia distance is a horizontal distance because a level instrument is used to collect the data.

  16. 1/2 Stadia

  17. Using 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.

  18. Calculating Horizontal Distance • To calculate horizontal distance you must know the slope distance and one additional bit of information for each station. Either: • % slope • or • Change in elevation • or • Vertical angle.

  19. Calculating Horizontal Distance --Percent slope

  20. Calculating Horizontal Distance--Difference in Elevation

  21. Calculating Horizontal Distance--Vertical Angle

  22. Questions ?

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