Section II Plotting Equipment and Firing Chart Preparation Some photomaps have spot altitudes, but interpolation for altitude is difficult and inaccurate. Determination of the scale of vertical control of photographs is discussed in FM 21-26. Normally, vertical control can be established by estimation only. Photomaps may include errors caused by tilt, distortion caused by relief, and errors caused by poor assembly, If points cannot be located on the photomap by inspection, the photomap scale must be determined before points can be located on the photomap survey. A photomap must not be considered exact until its accuracy has been verified. A photomap is a reproduction of an aerial photograph or a mosaic of aerial photographs on which grid lines, marginal information, and place names are superimposed. If a map is not based on accurate and adequate ground survey control, it should be used only to obtain approximate locations and vertical control to supplement a grid sheet firing chart.Ĭ. Deflections and azimuths are not affected. For example, if a 1:50,000-scale map is used, the ranges determined with the RDP must be doubled. If the map scale is other than 1:25,000, the range readings obtained from plotting equipment must be adjusted. Only maps based on accurate ground survey should be used for constructing firing charts. A map is a graphic representation, drawn to scale, of a portion of the earth's surface. The rightmost and topmost grid lines are not labeled because data are not determined from these grid lines.ī. The FDO assigns the lower left-hand corner casting and northing coordinates, and the direction of the long axis (east-west or north-south) also is specified. The grid sheet is numbered to correspond to the map area of the zone of operation of the supported force. The locations of all points plotted on the grid sheet must be determined either by survey data, map inspection, or firing. This scale provides the best compromise between accuracy and convenience and is therefore the scale for which standard plotting equipment is graduated. The intervals between these grid lines will create 1,000-meter grid squares on a scale of 1:25,000. A grid sheet is a plain sheet of paper or plastic (mylar) on which equally spaced horizontal and vertical lines, called grid lines, are printed. The most commonly used materials for constructing firing charts are as follows:Ī. Additional positions, fire support coordinating measures, and other data needed for the safe and accurate conduct of fire may also be recorded. 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. DescriptionĪ 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). The horizontal control operator (HCO) maintains the primary firing chart, and the vertical control operator (VCO) maintains a backup, or check, chart and a 1:50,000-scale situation map with tactical overlay(s). Regardless of the type constructed two firing charts are maintained in a manual FDC. They are surveyed firing charts and observed firing charts. Two types of firing charts may be constructed in the FDC. This section implements a portion of QSTAG 224. The determination of chart data requires the construction and operation of firing chart. Chart data consist of chart range, chart deflection, and angle T. One of the elements to the solution of the gunnery problem is the determination of chart data.
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