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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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