World War 2, Western Australia, Rottnest Island, Coast Artillery Instrumentation, Fortress Plotter No 2 Mk1

Overview

Fortress Plotter No 2 Mk1 – This mechanical instrument was constructed to a reduced scale with moving arms set to the bearings received from two fortress observation posts. Their intersection determined the co-ordinates of the target. Continuous plotting enabled course and speed to be determined. This plotter, with its five operators, was an upgrade to the Fortress Plotter No 1 located at the Bickley Point fortress plotting room.

Historical information

The Rottnest Island Fortress Plotting Room is a semi-buried complex within the Oliver Hill perimeter, built in 1936-38 and expanded in 1942.
A Fortress Plotting Room was where information about naval targets was received from Fortress Observation Posts, plotted and the required information extracted and then acted on. There are smaller plotting rooms associated with Bickley Battery which received information from the the Fortress Plotting Room and Battery Observation Posts.
The Fortress Plotting Room contained a Range-finding Exchange (telephone), Fortress Plotters to track shipping targets on charts, Fall-of-Shot Indicators, Fire Direction Table, Ballistic Correction Calculators and other equipment to collate incoming information about the type of target and its range, speed and course.

Details

Details

Registration number
cwa-org-32-54-688
Contextual Information

This entry is based on research, documentation and technical drawings prepared by John Mercer during many years as a leading member of the Rottnest Island Military Restoration Committee and the Defence Heritage Interpretation Plan Group.

Australian Army Museum of Western Australia

Australian Army Museum of Western Australia

Organisation Details
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Plotter No 2 Mk1
Fortress Plotter No 2 Mk 1
Layout
Layout of Fortress Plotting Room, Oliver Hill
Plotting Room Door

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