ATP-3-09-30 Observed Fires Download
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28 September 2017 ATP 3-09.30 A-1 Appendix A Observer Self-location Methods The observer can obtain an initial location by map-spot and compass, however, should refine the observation post location and the orientation of the laser rangefinder with more accurate means as soon as possible. If possible, observer location should be determined by survey. Lacking survey control, however, the observer has a variety of techniques available to self-locate. An observer should always use the most accurate means of self-location available that the situation permits. Observer coordinates (also called OBCO) should be sent to higher headquarters and the FDC (when in direct support) as set in unit SOP. It is recommended that this be no less than every 15 minutes or 500 meters travelled while patrolling. When in a static OP, location is sent upon initial establishment of the OP and needs to only be sent again if there is refinement to the initial grid or if the OP is moved. SELF-LOCATION BY USE OF TWO KNOWN POINTS A-1. The observer sends to the FDC the direction, distance, and vertical angle to two known points separated by at least 300 mils, and must also specify which known point is on the left. The FDC determines the laser rangefinder location. Then the FDC determines the correct orienting azimuth to one of the known points. This information is sent through secure means to the observer. The observer then plots their location on the map and reorients the laser rangefinder on the known point with the corrected azimuth. Self-location can be done by using two known points, one known point and one burst, or two bursts. Note. The observer’s location can also be determined by using only one point. However, the accuracy of the observer’s location depends on the accuracy of the initial azimuth orientation of the laser rangefinder. A-2. With this method, the observer uses two known points (see figure A-1 on page A-2). A known point may be established through survey, firing, or measuring from a map. If measured from a map, the point must be easily identifiable on the ground; for example, a church steeple, a water tower, or a prominent road junction. The observer must be sure of the ability to associate the known point on the ground with the same point on the map. This method of self-location is the most accurate and, therefore, the preferred technique. When using a voice call for fire, the observer will announce TRILATERATION in the method of fire.The observer sends to the FDC the direction, distance, and vertical angle to two known points separated by at least 300 mils, and must also specify which known point is on the left. The FDC determines the laser rangefinder location. Then the FDC determines the correct orienting azimuth to one of the known points. This information is sent through secure means to the observer. The observer then plots own location on the map and reorients the laser rangefinder on the known point with the corrected azimuth. Self-location can be done by using two known points, one known point and one burst, or two bursts.