text: Denied, Degraded and Disrupted Operations
  artillery safely, there is a person or persons designated to verify the task. Verification of data includes
  independent checks including:
  C-65. Independent checks are performed on each howitzer by the section chief to verify lay of the howitzer,
  emplaced retaining pins, prefire checks, charges, fuze settings, and set deflection and quadrant, as well as
  ensuring the announced firing data is applied as announced.
  C-66. Independent checks are also performed in the FDC where the database must be verified, either as the
  information is input or as a total review once the entire database has been constructed. The checks are
  continuous since the FDC must verify any additions, changes, or deletions to the database as they occur.
  C-67. A means to assist rapid transmission of commands to the howitzers are terrain gun position corrections.
  Terrain gun position corrections are individual howitzer corrections applied to the gunner's aid on the
  panoramic telescope (pantel), the correction counter on the range quadrant, and the fuze setting of each
  howitzer (TC 3-09.81). The digital link between the AFATDS and the howitzer will at some point fail to
  function. The problem may be in the AFATDS, one or more of the Gun Display Unit Replacement (referred
  to as a GDU-R), section chief display, or the communications link. When the failure occurs, voice fire
  commands must be transmitted to one or more of the howitzers. If the failure is at the AFATDS, voice
  commands must be transmitted to each of the howitzers. It is important that terrain gun position corrections
  be computed. These corrections, as a minimum, should be computed for the primary, left, and right sectors.
  C-68. During some types of degraded howitzer operations, the battery or platoon FDC may assume direct
  control of technical fire direction and send firing data to the howitzer. For example, if the digital control
  system of an individual howitzer section is degraded or inoperative, the FDC may compute technical firing
  data for that section. The preferred method requires an operational howitzer to locate next to the degraded
  howitzer and the degraded howitzer uses the operational howitzer's firing data. For more information see the
  appropriate technical manual for the specific cannon system and ATP 3-09.50.
  C-69. Manual backup should be established as a form of "position improvement" and should not impede
  setup or processing with automated means. The manual backup also serves as a basis of a rapid independent
  check to the automated solution. One of the elements to the solution of the gunnery problem is the
  determination of chart data. Chart data consists of chart range, chart deflection, and angle T. The
  determination of chart data requires the construction and operation of a firing chart.
  SECTION IV – FIRING CHARTS
  C-70. A firing chart is a graphic representation of a portion of the earth's surface used for determining
  distance (or range) and direction (azimuth or deflection) (TC 3-09.81). The chart may be constructed by using
  a map, a photomap, a grid sheet, or other material on which the relative locations of batteries, known points,
  targets, and observers can be plotted. Additional positions, FS coordinating measures, and other data needed
  for the safe and accurate conduct of fire may also be recorded.
  C-71. A surveyed firing chart is a chart on which the location of all required points (battery or platoon
  positions, known points, and observation points) are plotted (TC 3-09.81). These locations can be based on
  survey or map inspection. All plotted points are in correct relation to one another and reflect actual map
  coordinates.
  C-72. Chart data consist of chart range and chart deflection from the firing unit to the target and angle T. In
  a manual FDC, two firing charts will be constructed and used to check each other.
  C-73. One chart may differ slightly from another because of small differences in construction caused by
  human limitations in reading the graphical equipment. Because of these differences, the following tolerances
  between charts are permissible:
  * Range or distance ±30 m.
  * Azimuth or deflection ±3 mils.
  * Angle T ±30 mils.
  C-74. When survey control and maps are not available, delivery of indirect fires is possible by using observed
  firing charts. An observed firing chart is a firing chart on which all units and targets are plotted relative to
  each other from data determined by firing a registration (TC 3-09.81). Observed firing charts are an expedient