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66:(as in the battery illustrated at right). In a four-gun battery, the DP was often located midway between the two central guns. When the guns of a battery were more widely separated, the DP was often taken as a point on the ground perhaps 50 to 100 feet in front of the guns and more or less at the midpoint of the horizontal extent of the battery, visible from all of its guns. An example of such a directing point can be found at
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FORT STRONG USE 1934, was precisely surveyed by the U.S. Army
Engineers in 1934, and although it is not specifically identified as a directing point, there would have been little reason for the mark otherwise. The mark itself remained hidden up through 2010, but may still be in place. A description of the disk and its coordinates are contained
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The green arrow placed by Google Maps in its
Satellite view is located about 100-300 ft. in front of the (now empty) various gun positions of Batteries Ward and Hitchcock of Fort Strong, which mounted 10-inch disappearing guns from about 1905 until the 1930s. This position, marked by a disk labeled
237:, Note 1, at para. 28 ff. Since the azimuths and distances of the guns one from another were known, triangulation could be used to figure out the necessary aiming azimuths for each gun.
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Often the DP was taken as the pintle center of the right-most gun in a battery, as an observer looked over the battery towards the sea. In this case, the referenced gun was called the
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and telephoned to the battery or be performed at the guns. If the guns were relatively close to each other, then it might be enough to point them all at the same azimuth, to fire a
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See for example "FM 4-15: Coast
Artillery Field Manual, Seacoast Artillery, Fire Control and Position Finding," U.S. Government Printing Office, Washington, 1943, p. 20 ff.
155:'s target rod) was placed precisely over the DP marker so that the guns of the battery could sight on it and adjust the offsets of their gun sights.
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A cut-away drawing of a Coast
Artillery battery, showing its two base and stations (upper left), the plotting room (with plotting board), and the
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to identify a precisely surveyed point that was used as the point of reference for preparing the firing data used to aim the guns of a given
24:(DP) (between the two guns, at right). The directing point, on the surface of the blast apron, is indicated by the red dot. Each gun's
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Treatise on
Practical Solid Or Descriptive Geometry: Embracing Orthographic Projection and Perspective Or Radial Projection
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If the guns of a battery were widely separated, the firing data, computed for the DP, might have had to be corrected in
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The directing point for
Battery Stevenson at Fort Warren, Boston Harbor, set in the grass strip between its two guns.
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of the battery. The photo at left below illustrates a DP like this, between the two guns of
Battery Stevenson at
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A copper bolt set in concrete marks the DP for the mortars of
Battery Whitman at Fort Andrews in Boston Harbor.
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Often a target, for example a vertical wooden sighting panel (or a sighting pole, not unlike a
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The pintle center was the center of the gun pivot, mount point, or center of gravity of a gun.
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136:(USC&GS), often in the concrete blast slope or apron or in the ground in front of the
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In a two-gun battery, the DP was often located at a point midway between the two
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28:(the distance from the pintle center of the gun to the DP) is also indicated.
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for the various guns. These calculations could be performed in the
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124:Sometimes the DP was marked by a survey disk or a
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46:United States Army Coast Artillery Corps
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134:United States Coast and Geodetic Survey
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44:was a term used in the
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101:42.330081°N 70.95554°W
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106:42.330081; -70.95554
70:, a Coast Artillery
42:directing point (DP)
258:Artillery operation
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76:Long Island
68:Fort Strong
247:Categories
174:References
92:70°57′20″W
89:42°19′48″N
52:battery.
153:surveyor
160:azimuth
138:parapet
126:copper
235:Supra
168:salvo
206:here
72:fort
64:guns
40:The
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78:in
74:on
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82:(
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