FM-3-09 Fire Support and Field Artillery Operations Download
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Appendix C C-12 FM 3-09 30 April 2020 C-71. 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-72. 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 method that should only be use under emergency conditions and every attempt should be made to construct a surveyed firing chart as soon as possible. Since all locations are based upon firing data, observed firing charts contain errors because of nonstandard conditions. Manual gunnery methods are described in TC 3- 09.81.