Mapping Unit Review

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”?

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 16 th of an inch). b) What would be the actual field distance between two trees that are 4-1/4” apart on the map?

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. 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

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)

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

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. Describe how you can lay out a 90  corner using rulers or tapes (chains). Ans: set up your measurements in ratios of 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. 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

Find the Corner Angle. 17’7” 10’