There are three situations in which target reading, rather than direct reading, is done on the face of the rod: When  the  rod  is  too  far  from  the  level  to  be read  directly  through  the  telescope: When a reading to the nearest 0.001 foot, rather than  to  the  nearest  0.01  foot,  is  desired  (a vernier on the target or on the back of the rod makes  this  possible; When  the  instrumentman  desires  to  ensure against  the  possibility  of  reading  the  wrong foot  (large  red  letter)  designation  on  the  rod. For target readings up to 7.000 feet, the rod is used fully closed, and the rodman, on signals from the instrumentman, sets the target at the point where its horizontal axis is intercepted by the cross hair, as seen through the telescope. When the target is located, it is clamped  in  place  with  the  target  screw  clamp,  as shown  in  figure  5-9. When  a  reading  to  only  the nearest  0.01  foot  is  desired,  the  graduation  indicated by the target’s horizontal axis is read; in figure 5-9, this reading is 5.84 feet. If reading to the nearest 0.001 foot is desired, the rodman reads the vernier (small scale running from 0 to 10) on the target. The 0 on the vernier indicates that  the  reading  lies  between  5.840  feet  and  5.850 feet. To determine how many thousandths of a foot over 5.840 feet, you examine the graduations on the vernier to determine which one is most exactly in line with a graduation (top or bottom of a black dash) on the rod. In figure 5-9, this graduation on the vernier is the  3;  therefore,  the  reading  to  the  nearest  0.001  foot is 5.843 feet. For target readings of more than 7.000 feet, the procedure  is  a  little  different.  If  you  look  at  the left-hand view of figure 5-8 (showing the back of the rod),  you  will  see  that  only  the  back  of  the  upper section  is  graduated,  and  that  it  is  graduated downward from 7.000 feet at the top to 13.09 feet at the bottom. You can also see there is a rod vernier fixed to the top of the lower section of the rod. This vernier is read against the graduations on the back of the upper section. For a target reading of more than 7.000 feet, the rodman first clamps the target at the upper section of the rod. Then, on signals from the instrumentman, the rodman extends the rod upward to the point where the horizontal axis of the target is intercepted by the cross hair. The rodman then clamps the rod, using the rod clamp  screw  shown  in  figure  5-13,  and  reads  the vernier  on  the  back  of  the  rod,  also  shown  in  that figure. In this case, the 0 on the vernier indicates a certain  number  of  thousandths  more  than  7.100  feet. Remember, that in this case, you read the rod and the vernier down from the top, not up from the bottom. To   determine   the   thousandths,   determine   which vernier  graduation  lines  up  most  exactly  with  a graduation  on  the  rod. In  this  case,  it  is  the  7; therefore, the rod reading is 7.107 feet. Rod Levels A  rod  reading  is  accurate  only  if  the  rod  is perfectly plumb (vertical) at the time of the reading. If the rod is out of plumb, the reading will be greater than the actual vertical distance between the height of Figure 5-13.—Philadelphia rod target reading of more than 7.000 ft. 5-8