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Coast Artillery fire control system
In the U.S. Army Coast Artillery Corps, the term fire control system was used to refer to the personnel, facilities, technology and procedures that were used to observe designated targets, estimate their positions, calculate firing data for guns directed to hit those targets, and assess the effectiveness of such fire, making corrections where necessary.
The Coast Artillery's early fire control instruments supported optical rangefinding and position finding, either horizontal base or vertical base, with both systems usually present for each fort. Early horizontal base rangefinding required two azimuth (a.k.a. bearing or deflection) instruments, preferably widely separated, and a communications system to transmit data to a plotting room and then to the guns. The instruments were often in bunkers called base end stations, as they defined the endpoints of a baseline. A base end station might be a two-story structure with a plotting room or other instruments or facilities on the lower level. By the 1920s coincidence range finders, self-contained horizontal base instruments, were in use along with the other methods. Though these could be used quickly, these had baselines of only a few feet, reducing their accuracy and maximum effective range.
Vertical base rangefinding used a single depression position finder (DPF) mounted as high as possible above the water level; these were derived from similar British devices and adopted beginning in 1896. Along with the target's azimuth, they measured the vertical angle from the instrument to the target; with the instrument's height above water known, this determined the target's range. The need to be progressively higher above water as gun ranges increased was a severely limiting factor for the DPF, and they were usually supplemented by horizontal base systems. As gun ranges continued to increase, in the 1920s additional horizontal and vertical base systems were installed, in tall fire control towers at some locations, including the Harbor Defenses of Portsmouth (New Hampshire) and the Harbor Defenses of the Delaware.
By World War II, radar had become a better method of determining a target's position. However, in the bombardment of Fort Stevens by a Japanese submarine on 21 June 1942, the only time a coastal defense installation in the contiguous United States was attacked, the fort's commander used a DPF to determine that the submarine was out of range, and thus did not return fire.
Plotting rooms were used by the Coast Artillery Corps to house a team of soldiers who were engaged in controlling fire for the guns of a coastal artillery battery. Plotting rooms were in use from about 1895 through the end of WWII, at which point the U.S. Coast Artillery was disbanded. In some newer Coast Artillery batteries during World War II, these rooms were called Plotting, Switchboard, and Radio (PSR) rooms, and were often (but not always) integrated with the bunkers at the battery that were also used for ammunition storage, electrical generators, and other support functions. For 16-inch guns, the PSR bunker was some distance from the gun battery bunker, to avoid the shock of firing interfering with the plotting room equipment.
A plotting room was connected by telephone lines (and sometimes by radio) to base end stations that observed the locations of enemy ships and sent data to plotting room soldiers who used equipment such as plotting boards to calculate where the guns should be pointed and when they should be fired. Telephone lines also ran from the plotting room to the guns and were used to relay firing data. Other devices, like "range correction boards" or "deflection boards", were used in the plotting room to calculate corrected firing data (described below) or to adjust range and azimuth after spotters in remote observing stations observed where prior shots had fallen.
Plotting rooms were sometimes made of concrete and buried below ground (for protection) or were located in the reinforced concrete casemates of coast artillery batteries. Plotting rooms were also located in free-standing structures, either low towers or one- or two-story wood and plaster buildings, which might house facilities for several batteries near each other in barracks-like structures. These multiple-battery installations might also have sleeping quarters and latrine facilities nearby. Sometimes plotting rooms were located hundreds of yards from the batteries they controlled. They often sat on top of nearby hills or ridge lines.
Gun data computers were electro-mechanical computers were introduced into the Coast Artillery in the 1940s, particularly in the new 100- and 200-series 16-inch and 6-inch gun batteries that became operational during that period. Some of these computers received data directly from communicators that were connected to observation instruments in fire control stations or from Coast Artillery radar equipment.
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Coast Artillery fire control system
In the U.S. Army Coast Artillery Corps, the term fire control system was used to refer to the personnel, facilities, technology and procedures that were used to observe designated targets, estimate their positions, calculate firing data for guns directed to hit those targets, and assess the effectiveness of such fire, making corrections where necessary.
The Coast Artillery's early fire control instruments supported optical rangefinding and position finding, either horizontal base or vertical base, with both systems usually present for each fort. Early horizontal base rangefinding required two azimuth (a.k.a. bearing or deflection) instruments, preferably widely separated, and a communications system to transmit data to a plotting room and then to the guns. The instruments were often in bunkers called base end stations, as they defined the endpoints of a baseline. A base end station might be a two-story structure with a plotting room or other instruments or facilities on the lower level. By the 1920s coincidence range finders, self-contained horizontal base instruments, were in use along with the other methods. Though these could be used quickly, these had baselines of only a few feet, reducing their accuracy and maximum effective range.
Vertical base rangefinding used a single depression position finder (DPF) mounted as high as possible above the water level; these were derived from similar British devices and adopted beginning in 1896. Along with the target's azimuth, they measured the vertical angle from the instrument to the target; with the instrument's height above water known, this determined the target's range. The need to be progressively higher above water as gun ranges increased was a severely limiting factor for the DPF, and they were usually supplemented by horizontal base systems. As gun ranges continued to increase, in the 1920s additional horizontal and vertical base systems were installed, in tall fire control towers at some locations, including the Harbor Defenses of Portsmouth (New Hampshire) and the Harbor Defenses of the Delaware.
By World War II, radar had become a better method of determining a target's position. However, in the bombardment of Fort Stevens by a Japanese submarine on 21 June 1942, the only time a coastal defense installation in the contiguous United States was attacked, the fort's commander used a DPF to determine that the submarine was out of range, and thus did not return fire.
Plotting rooms were used by the Coast Artillery Corps to house a team of soldiers who were engaged in controlling fire for the guns of a coastal artillery battery. Plotting rooms were in use from about 1895 through the end of WWII, at which point the U.S. Coast Artillery was disbanded. In some newer Coast Artillery batteries during World War II, these rooms were called Plotting, Switchboard, and Radio (PSR) rooms, and were often (but not always) integrated with the bunkers at the battery that were also used for ammunition storage, electrical generators, and other support functions. For 16-inch guns, the PSR bunker was some distance from the gun battery bunker, to avoid the shock of firing interfering with the plotting room equipment.
A plotting room was connected by telephone lines (and sometimes by radio) to base end stations that observed the locations of enemy ships and sent data to plotting room soldiers who used equipment such as plotting boards to calculate where the guns should be pointed and when they should be fired. Telephone lines also ran from the plotting room to the guns and were used to relay firing data. Other devices, like "range correction boards" or "deflection boards", were used in the plotting room to calculate corrected firing data (described below) or to adjust range and azimuth after spotters in remote observing stations observed where prior shots had fallen.
Plotting rooms were sometimes made of concrete and buried below ground (for protection) or were located in the reinforced concrete casemates of coast artillery batteries. Plotting rooms were also located in free-standing structures, either low towers or one- or two-story wood and plaster buildings, which might house facilities for several batteries near each other in barracks-like structures. These multiple-battery installations might also have sleeping quarters and latrine facilities nearby. Sometimes plotting rooms were located hundreds of yards from the batteries they controlled. They often sat on top of nearby hills or ridge lines.
Gun data computers were electro-mechanical computers were introduced into the Coast Artillery in the 1940s, particularly in the new 100- and 200-series 16-inch and 6-inch gun batteries that became operational during that period. Some of these computers received data directly from communicators that were connected to observation instruments in fire control stations or from Coast Artillery radar equipment.