text: Appendix C
  The deviations noted do not invalidate the met message but should be referred to the BN FDC for
  clarification, especially in cases where the message was transmitted verbally.
  C-58. In cases where the met message's validity is called into question, the fire direction officer has a few
  available options.
  * If this is the first met message and it cannot be checked against previous met data, a precision
  registration should be conducted in order to account for all nonstandard conditions. If a registration
  is not feasible and line to line errors are in question, the met may be applied and a check round
  fired to verify accuracy.
  * If the met in question is not the first produced by the CMD-P and the FDC has maintained accuracy
  during fire mission processing with the current met, a dry-fire verification may be conducted in
  order to compare firing solutions. With the current met, compute and record firing data (deflection,
  quadrant elevation, and time fuze setting) for a known point. Next, make the new met current and
  compute firing data for the same known point, comparing the two firing solutions. As a general
  rule, apply the standard tolerances for deflection (±3 mils), quadrant elevation (±3 mils), and time
  fuze setting (±0.1 seconds).
  Note. Additional analysis may be needed when firing at maximum ranges, where each mil causes
  a greater deviation on the ground. Use the appropriate TFT to compare the differences in firing
  data at the known point target range.
  C-59. The fire direction officer also maintains the option to discard the new met and continue firing with the
  current met while maintaining accuracy. While made feasible by the ability of the CMD-P to provide a new
  met every 30 minutes, the FDC should strive to improve accuracy with every chance afforded.
  C-60. The passage of time may decrease the accuracy of a MET message because of the changing nature of
  weather. With existent equipment and technology, the BN FDC has the ability to provide met messages every
  30 minutes. A met message at this frequency has been shown to dramatically increase the accuracy and
  lethality of munitions. This however may be impractical and could slow the responsiveness of the firing unit.
  A firing unit should request a new met message every 2 to 4 hours, depending on the tactical situation.
  C-61. It is critical for a firing unit to request and receive a met message when:
  * Upon entering the initial firing position.
  * Any movements more than 4 kilometers, but the target area remains the same.
  * Anytime direction of fire is more than 800 mils from the original target location.
  * Anytime there is a significant change in weather; that is, a front comes through, or the temperature
  increases or decreases.
  * During transition periods.
  MANUAL COMPUTATION OF MET
  C-62. For manual MET procedures use DA Form 4200 (Met Data Correction Sheet) as outlined in TC 3-
  09.81.
  ACCURATE COMPUTATIONAL PROCEDURES
  C-63. The computation of firing data similarly affects all indirect fire systems, to include mortars, and must
  be accurate. Accurate computational procedures are provided by all FDCs. Automated and manual techniques
  are designed to achieve accurate and timely delivery of fire. The balance between accuracy, speed, and the
  other requirements for accurate fire should be included in the computational procedures.
  C-64. In order to reduce firing incidents is to recognize that individuals make errors, and the best safeguard
  against those errors is an independent double check of all operations in which human error could cause a
  firing incident (sometimes referred to as the two-man rule). A fundamental aspect of safety is that no one
  person performs a critical live fire task then checks that task alone. For every critical task required for firing