ATP-3-09-30 Observed Fires Download
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Crater and Shell Fragment Analysis and Reports 28 September 2017 ATP 3-09.30 B-5 Figure B-4. Ricochet furrow method Mine Action B-13. This occurs when a shell burst beneath the ground. Occasionally, such a burst will leave a furrow which can be analyzed in the same manner as the ricochet furrow. A mine action crater which does not have furrow cannot be used to determine the direction to the weapon. HIGH-ANGLE SHELL CRATERS (MORTARS) B-14. In a typical mortar crater, the turf at the forward edge (the direction away from the hostile mortar) is undercut. The rear edge of the crater is shorn of vegetation and grooved by splinters. B-15. When fresh, the crater is covered with loose earth, which can cover the firm, burnt inner crater. The ground surrounding the crater is streaked by splinter grooves that radiate from the point of detonation. The ends of the splinter grooves on the rearward side are on an approximately straight line. This line is perpendicular to the line of flight if the crater is on level ground or on a slope with contours perpendicular to the plane of fire. B-16. A fuze tunnel is caused by the fuze burying itself at the bottom of the inner crater in front of the point of detonation. B-17. Three methods may be used to determine direction from a mortar shell crater-the main axis, splinter groove, and fuze tunnel methods. Main Axis Method B-18. The four steps to determine direction by the main axis method (see figure B-5 on page B-6) areas follow: Lay a stake along the main axis of the crater, dividing the crater into symmetrical halves. The stake points in the direction of the mortar. Set up a direction-measuring instrument in line with the stake and away from fragments. Measure the direction to the weapon.