CHAPTER  12 DIRECT LINEAR MEASUREMENTS AND FIELD SURVEY SAFETY This  chapter  covers  the  various  duties,  the techniques, and the skills a chaining crew member must  learn  thoroughly  concerning  chaining  opera- tions  and  some  of  the  devices  used  in  chaining itself.  DIRECT  LINEAR  MEASUREMENTS,  as used   in   this   chapter,    are  methods  used  for measuring  horizontal  distances  with  a  tape  (or chain) and/or with electronic distance-measuring instruments presently available in the military. As a crew member, you should be concerned not  only  about  the  task  at  hand  but  also  about the  potential  hazards  to  which  you  may  be exposed  in  the  field.  It  is  important,  therefore, that  you  recognize  the  precautions  and  safety measures applicable to the survey field crew. In this  chapter  we  shall  discuss  these  precautions and  safety  measures  and  also  additional  duties normally  performed  by  the  crew. DUTIES  OF  A  CHAINING CREW  MEMBER During   a   typical   chaining   operation,   it   is possible that many and varied duties other than the actual chaining itself are to be undertaken as part  of  the  whole  process.  To  prepare  the  field chaining party for the task ahead, we shall present some  of  these  duties,  as  applicable.  In  some cases,  these  duties  can  be  modified  or  tailored, contingent  upon  the  mission,  terrain  features,  and other  conditions  that  may  affect  the  speed  and accuracy  of  the  operation. GIVING  HAND  AND  VOICE  SIGNALS During   fieldwork,   it   is   essential   that   you communicate   with   the   other   members   of   the survey party over considerable distances. Some- times  you  may  be  close  enough  to  use  voice communication;  more  often,  you  will  use  hand signals.  Avoid  shouting;  it  is  the  sign  of  a beginner. Standard voice signals between chain- men must be used at all times to avoid misunder- standing.  There  are  also  several  recommended hand signals, most of which are shown in figure 12-1. Those shown are recommended, but any set of signals mutually agreed upon and understood by all members of the party can also be used. It is  important  to  face  the  person  being  signaled. Sometimes, if it is difficult for you to see the other person,  it  helps  to  hold  white  flagging  in  your hand  when  giving  signals.  When  signals  are  given over snow-covered areas, red or orange flagging is  more  appropriate. Explanations  of  the  hand  signals  shown  in figure  12-1  are  as  follows: 1.  ALL  RIGHT.  The  “all  right”  is  given  by the  instrumentman  when  the  alignment  is  OK  for a plumb line, a range pole, a stake, a hub, or any other  device  used  as  a  target,  or  when  the instrumentman has finished all activities at your location. It is given by waving both arms up and down while extending them out horizontally from the shoulders. If the instrumentman, in aligning a target, extends both arms out horizontally from the  shoulders  without  waving  them,  the  signal means that the target should be held steady while a  quick  check  of  its  position  is  being  made. 2.  MOVE  RIGHT  OR  LEFT.  This  signal  is given by the instrumentman when lining in a target on a predetermined line. It is given by moving the appropriate hand outward from the shoulder. A slow  motion  of  the  hand  means  that  you  must move   a   long   distance;   a   quick,   short   motion means  that  you  must  move  a  short  distance. 3.  GIVE  ME  A  BACKSIGHT.  This  signal is given when the instrumentman wants a target held at a previously located point. It is given by extending one arm upward with the palm of the hand  forward. 4.  GIVE  ME  A  LINE  OR  THIS  ISA  HUB. This signal, given by the rodman or the chainman, is intended to indicate a hub or to ask for a line on  the  point  indicating  the  exact  location. It   is   given   by   holding   a   range   pole horizontally  overhead,  then  moving  it  to  a  vertical 12-1