TM 1-1510-218-10 3-76 Table 3-17.  GPS Status Codes DISPLAY EXPLANATION ACQ Acquisition DEGRD Navigation with position degradation FAILR Receiver failure INIT Initialization NAV Navigation NAV A Navigation with altitude aiding NAV D Navigation with data collection TRAN Transition In the initialization stage, the GPS receiver is in the   process   of   initializing   and   collecting   information such  as  the  date,  time,  and  last  position.    Next  the receiver    collects    data    from    its     own    memory    to determine   which   satellites   should   be   visible.      After completing    the    initialization    process,    the    receiver begins  the  acquisition  process.    During  this  time,  the visible   satellites   are   being   acquired   and   data   from them is being obtained. The    transition    stage    indicates    an    adequate number  of  satellites  for  navigation  has  been  acquired and is being tracked, but no position data can yet be produced. Normal navigation is indicated by a NAV, NAV A, or  a  NAV  D  GPS  state.    NAV  A  indicates  that  the altitude  input  is  being  used  in  the  position  solution.   NAV D indicates that besides calculating position, the receiver    is    collecting    and    storing    in    its    memory ephemera and almanac data information. The  specific  GPS  satellites  or  Space  Vehicles (SV),  being  received are displayed in the left column.   Each  satellite  has  its  own  identification  number.    An asterisk   (*)   to   the   left   of   the   satellite   indicates   this particular  satellite  is  not  presently  being  used  in  the navigation solution. The  satellite's  health,  transmitted  by  satellite,  is indicated  to  the  right  of  the  satellite  number.    Health designators are defined in Table 3-18. The    Signal    to    Noise    Ratio    (SNR)    for    each satellite   being   received   is   displayed   in   the   middle column   and   indicates   the   signal   strength   for   each satellite.  The higher the SNR value, the stronger the signal.  Values usable for navigation will be in the mid 30's  to  50's.    Typical  values  are  in  the  middle  of  this range. Table 3-18.  Satellite Health DISPLAY EXPLANATION B Bad W Weak – Unknown Blank Good The elevation (ELE) above the horizon for each satellite  is  provided  in  the  right  column  and  will  range from 5 ° to 90°.  Refer to Figure 3-111. (2)   STA  2  Page.    The  STA  2  page  displays the systems estimate of the position error expressed in nautical miles.  Refer to Figure 3-112.  The KLN 90B's position error depends on such factors as the number of  satellites  being  received,  the  strength  of  the  GPS signals,  and  the  geometry  of  the  satellites  presently being used for navigation. STA+1 STATE   NAV SV SNR ELE 02  40 11^o 11  42 47^o 16  36 06^o *18B 33 65^o Figure 3-111.  STA 1 Page STA 2 ESTIMATED POSN ERROR       .07NM Figure 3-112.  STA 2 Page