Australian Army Museum of Western Australia > Records

World War 2, Western Australia, Rottnest Island, Oliver Hill, Fortress Plotting Room (Primary), Layout, 1942

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Subcollections

Coast Artillery Fire Control - Target and Projectile Coincidence

Overview

Layout diagram of Fortress Plotting Room at Oliver Hill. The Fortress Plotting Room construction commenced in late 1942 adjacent to the existing Oliver Hill battery plotting room. In 1943 it became operational along with an auxilliary fortress plotting room at Bickley Point. The function of the Fortress Plotting Room was to determine the current position, course and speed of a target using the data from distant fortress observation posts positioned throughout Rottnest Island. This information was relayed to the selected engaging battery in the Fortress system by means of head-breast phones

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

Registration number

cwa-org-32-54-690

Inscriptions and markings

This installation at Wadjemup Hill / Signal Ridge was the primary Fortress Plotting Room. For redundancy and emergency back-up, a secondary Fortress Plotting Room was located within the Bickley Battery complex.

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.

Geotag

-32.008490251366, 115.51400708229

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Links to additional resources

Instrument - Fortress Plotter (Aust) 101 Mk 1

Instrument - Fortress Plotter (Aust) 102 Mk 1

Instrument - Fortress Plotter No 2 Mk1

Instrument - Encoder - Fall of Shot Mk1

Australian Army Museum of Western Australia

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