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“Bite-Size Bits of Local, National, and Global History”
Dover in Kent, England, United Kingdom
 

Finding the Enemy

 
 
Finding the Enemy Marker image. Click for full size.
By Michael Herrick, September 8, 2018
1. Finding the Enemy Marker
Inscription.
Finding the Enemy
This tiny structure, a Position-Finding (PF) Cell, performed a major role in the period 1891-1918. It was used to pinpoint the position of enemy ships and to relay that information to the coast defence guns at Langdon Battery, 1km to the east.

An observer at the window used a receiving instrument with telescope to locate a suspect ship. The instrument calculated the bearing to the ship. This cell received bearings transmitted electrically from an identical cell some distance away. The distance between the two cells was known, and so it was easy to fix the position of the ship by triangulation. The data was transferred electrically to dials next to the guns, enabling the gun crews to aim and fire at the ship.

By taking repeated readings, the ship's course and speed could be calculated, the gun aimed at a predicted position and fired, even when the gun crew couldn't see the ship.

( photo captions )
- This drawing, dated 1897, is a section through a PF Cell showing details of its fittings and construction.
- A receiving instrument from a PF cell. The telescope allowed tracking of the target while the electrical wire brought data from another PF Cell (the transmitting cell). The data was combined on a map under the telescope and the target position fixed.
Finding the Enemy Marker image. Click for full size.
By Michael Herrick, September 8, 2018
2. Finding the Enemy Marker
The Position-Finding (PF) Cell is behind the marker.

- This PF Cell was later adapted for a depression range finder (DRF), which worked out the target position by trigonometry from just one PF Cell. A DRF (pictured left) was mounted on the surviving concrete pillar in the building.
 
Location. 51° 7.609′ N, 1° 19.506′ E. Marker is in Dover, England, in Kent. Marker can be reached from the intersection of Castle Hill Road and Canons Gate Road, on the left when traveling south. Touch for map. Located at the Hospital Battery at the cliff’s edge next to Dover Castle. Marker is in this post office area: Dover, England CT16 1HU, United Kingdom.
 
Other nearby markers. At least 8 other markers are within walking distance of this marker. The Signal Platform (a few steps from this marker); A View to the East (a few steps from this marker); A View of the Harbour (a few steps from this marker); A View to the West (a few steps from this marker); Command, Control and Communication (a few steps from this marker); Fighting the Enemy in the Sky (within shouting distance of this marker); Operation Dynamo (within shouting distance of this marker); Ramsay: retreat and return (within shouting distance of this marker). Touch for a list and map of all markers in Dover.
 
Also see . . .
1. English Heritage - Dover Castle. (Submitted on January 11, 2019, by Michael Herrick of Southbury, Connecticut.)
View from the Position-Finding Cell image. Click for full size.
By Michael Herrick, September 8, 2018
3. View from the Position-Finding Cell
Dover Harbour and the English Channel. France is just visible on the horizon.

2. Dover Castle on Wikipedia. (Submitted on January 11, 2019, by Michael Herrick of Southbury, Connecticut.)
 
Categories. War, World I
 
 
Credits. This page was last revised on January 11, 2019. This page originally submitted on January 11, 2019, by Michael Herrick of Southbury, Connecticut. This page has been viewed 59 times since then. Photos:   1, 2, 3. submitted on January 11, 2019, by Michael Herrick of Southbury, Connecticut.
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