• Home
  • Download PDF
  • Order CD-ROM
  • Order in Print
Figure  13-9.-Three  types  of  horizontal  limb  graduations.
Figure  13-12.-Sample  field  notes  from  a  deflection  angle  transit-tape  survey.

Engineering Aid 3 - Beginning Structural engineering guide book
Page Navigation
  413    414    415    416    417  418  419    420    421    422    423  
Figure  13-10.-Setting  the  vernier  at  zero-zero. The  horizontal  limb  is  paired  with  another circle  (the  vernier  plate),  which  is  partially graduated  on  either  side  of  zero  graduations located   180°   apart   on   the   plate.   When   the telescope is in the normal (upright) position, the A vernier is located vertically below the eyepiece, and the B vernier, below the objective end of the telescope. The zero on each vernier is the indicator for reading the sizes of horizontal angles turned on  the  horizontal  limb. Figures  13-10  and  13-11  illustrate  the  method of turning an angle of 30° from a reference line with a transit. 1.  With  the  transit  properly  set  over  the  point or  station,  bring  one  of  the  horizontal  verniers near zero by hand; clamp the upper motion; and, by  turning  the  upper  tangent  screw,  set  one vernier at 0°, usually starting with the A vernier (fig. 13-10). Train the telescope to sight the marker (range pole, chaining pin, or the like) held on the reference  line;  clamp  the  lower  motion;  and,  by using the lower tangent screw, set the line of sight on the marker. Figure 13-11.-Setting an angle exactly on the vernier zero. 2.  Release  the  upper  motion  and  rotate  the telescope to bring the zero on the A vernier in line with th3 30° graduation on the horizontal limb, as  shown  in  figure  13-11.  To  set  the  vernier exactly at 30°, use the upper tangent screw. You may use a magnifying glass to set the vernier easily and  accurately. 3.  Mark  the  next  point  with  a  marker,  and follow the procedures for establishing a point or station. Similarly, you may use the procedures above to measure a horizontal angle by sighting on two existing points and reading their interior angle. In  addition,  the  following  hints  may  help  you when  you  are  taking  horizontal  measurements: 1. Make the centering of the line of sight as close as possible by hand so that you will not turn the  tangent  screw  more  than  one  or  two  turns. Make  the  last  turn  of  the  tangent  screw  clockwise to  compress  the  opposing  springs. 13-10







Western Governors University

Privacy Statement
Press Release
Contact

© Copyright Integrated Publishing, Inc.. All Rights Reserved. Design by Strategico.