Identifying Chaining Mistakes and Errors

Solving Surveying Problems by Tape

Caring for and Maintaining a Survey Tape

Engineering Aid 3 - Beginning Structural engineering guide book
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First, solving for we have Since Reference to a table of natural functions shows that the angle with cos equal to 0.87872 measures, to the nearest 1 min., 28°29´. The intervals measured off from A were made equal for mere convenience. The solution will work just as well for unequal intervals. In determining the size of an angle by the tangent method, you simply lay off a right triangle and solve for angle A by the common tangent solution. Suppose that in figure 12-20, you want to determine the size of angle A. Measure off AC a convenient length (say, 80.0 ft). Lay off CB perpendicular to AC and measure it; say it measures 54.5 ft, as shown. The angle is computed by using the following formula: The angle with tangent 0.68125 measures 34°18´. Figure 12-20.-Determining the size of an angle by the tangent method. LAYING OFF AN ANGLE OF A GIVEN SIZE.— An angle of a given size can be laid off by tape by applying the tangent right triangle solution. Suppose that in figure 12-21, you want to lay off a line AC from A, 25° from line AB, Again measure off a convenient 80.0 ft from A to establish point B. Erect a perpendicular from B as shown by the dotted line. You want to measure off along this perpendicular side a (opposite side), the distance that, when divided by the adjacent side, will give the value of the natural tangent of 25°. Use the following formula: Measure off 37.3 ft from B to establish point C. A line from A through C will form an angle of 25° from AB. Identifying Chaining Mistakes and Errors In surveying, distinctions are made between ERRORS and MISTAKES. Errors are caused by factors such as the effects of nature, the physical condition of the personnel performing the survey, and the condition of your instruments. Mistakes, however, are simply human blunders. While errors may be compensated for, mistakes can be detected, correct, and better yet, prevented only by the exercise of care. COMMON MISTAKES.— Mistakes may result from poor work habits, lack of judgment, or confusion. They are often costly, time con- suming, and difficult to detect. The easiest way to avoid them is to establish a definite procedure and follow it, being constantly alert during the Figure 12-21.-Laying off an angle of a given size. 12-22

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