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Mapping Unit Review

Learn how to calculate elevations, distances, bearings, and angles in land surveying. Understand scale conversions and accurate measurements using compass and level readings.

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Mapping Unit Review

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  1. Mapping Unit Review

  2. Problem 1 • 1.A level is set up on a job site and a reading is taken off the benchmark. The reading on the rod is found to be 3’- 5” and the benchmark is at an elevation of 1062’- 4”. • A) what is the elevation if the rod measures 6’ 9”? • B) What should the rod read if the elevation is 1060’ 8”?

  3. Problem 2 • 2.On a map using a scale of 1 in. = 15 ft.: • a)How long would you draw a fence line that was 82’- 6” long in the field? (answer to the nearest 16th of an inch). • b)What would be the actual field distance between two trees that are 4-1/4” apart on the map?

  4. Essay/short answer • 3.Describe how to find a bearing, relative to true North, in the field using a compass. • Ans: Take the compass reading of your object and add that location’s angle of declination. • 4.Explain how to find the angle of declination for a given location. • Ans: 1. Identify a place where true north is known. Find the compass reading for that direction. Subtract the compass reading from 360 degrees.

  5. 5. Explain each step to set up the transit/level so a person can read your directions and be able to erect it correctly. • Ans: see ppt. on T/L

  6. Short answer/Essay • 6.Describe at least two ways to find the angle of a corner, in complete detail so another person could follow your direction and accomplish it. • Method (I): • 1. Take the compass reading for both fence/ property lines, pointing into the corners. • 2. Subtract the compass readings and you have your corner angle. (not very accurate)

  7. Method (II) • 1. Measure 10 feet from the corner on both fences/property lines. • 2. Measure the triangular distance between the ten foot marks. • 3. Draw the resulting isosceles triangle and insert the altitude of the vertex angle. (This line is the angle bisector, and the perpendicular bisector of the base). • continued

  8. Corner angle method II (cont’) • 4. Draw the resulting right triangle from half the isosceles triangle. Use the definition of sine to solve for half the corner angle: sinθ = (opp. side/ hyp.) So, θ = sin-1(O/H) • 5. Double the half angle to get the corner angle.

  9. 9.Describe how you can lay out a 90 corner using rulers or tapes (chains). • Ans: set up your measurements in ratios of 3-4-5. Measure 4 feet along a fence from a specific point. From the same point measure out 3 feet approximately 90 degrees. From the ends of the 3 and 4 foot tapes you will measure 5 feet.

  10. 10.Describe the procedure to find the bearing and heading of a fence line or property line. • Ans: Find the compass reading and add the angle of declination. The heading starts with north or south and ends with east or west. i.e. N 9° E

  11. Find the Corner Angle. 10’ 10’ 17’7”

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