Semaphore project - conceptual story

The semaphore installation was born from a desire to work with augmented reality technology. I also wanted to create an interactive work that was fully immersive.


The primary concept
Augmented reality enables virtual content to be overlaid over the real world, in real time. There are several methods to position virtual content in relation to the real world, one method is to use visual markers. Visual markers enable specific virtual objects to be positioned in specific locations, in relation to the real world. Markers are, in essence, flags that a computer program can detect.

I wanted the markers to be directly incorporated into the art concept, so I investigate historic uses of flags. A memory surfaced about flags being used to transmit the time of day between English cities. Research led to the discovery of the shutter telegraph that was used between the end of the 18th century and the beginning of the 19th century.

A shutter telegraph tower, showing six mechanical flags - image from 'The Semaphore' by T.W. Holmes.

The shutter telegraph was used to transmit coded messages between towns and cities in the south of England. On a clear day, the shutter telegraph was much faster than a relay of riders on horseback. And because messages could be relayed quickly the shutter telegraph became an essential military tool. Shutter tower operators could, for example, quickly warn the Admiralty, in London, if there was an invasion coming from the English Channel, or the southern region of the North Sea. Day-to-day the shutter telegraph was used to transmit various messages between a selection of towns and cities, and acted as a chronograph.

The Admiralty London Shutter Telegraph System - map based on information from, 'The Old Telegraphs,' by Geoffrey Wilson, 'The Semaphore,' by T.W. Holmes, 'Military Signals from the South Coast,' by John Goodwin, and conversations with Paul Taylor (Curator of Chatley Heath Semaphore Tower, Chatley, England).

Finding out about the historic shutter telegraph was fortunate because there turned out to be a striking visual resemblance between the historic mechanical flags/panels used in these telegraph systems, and typical, current day, augmented reality markers; both are black and white, and square in shape.

Original shutter telegraph mechanical flag

Typical augmented reality marker designs

Finding this similarity intriguing I decided to build an installation containing three shutter telegraph towers.


The concept behind the headset
Three shutter towers enable the art viewer to position themselves at the central tower, as if they were the 'glass' man.

Traditionally the 'glass' man would:

• look up and down the shutter tower line, with a telescope, to see if a message needed to be relayed to an adjacent tower
• tell the 'rope' man, which shutters to operate, so as to pass on the message
• check that the message the 'rope' man had sent had been correctly passed on by the next tower

The art viewer, instead of using a telescope, dons a virtual reality headset. A headset was chosen, instead of a computer screen, because it gives the art viewer a fully immersive experience.

Art viewer wearing the virtual reality headset

The concept behind the tower markers
I envisaged that each tower would have six double sided panels/markers, as per the original design, with the marks on each panel staying true to that design. This would mean that all the six panels on each tower would be identical. However, technology constraints of the AR toolkit meant that each panel needed to be different. A solution was found by superimposing additional marks onto the panels. These marks resembled marks from the semaphore telegraph system, a communication method that superseded the shutter telegraph.

The final design of the installations tower markers

The concept behind the 3D virtual content of the tower markers
The tower panels were designed to trigger virtual content. The virtual content would:

• represent the transmission of data from one tower to another
• reference what would have been transmitted in real life i.e. photons
• display 3D objects, to symbolise packets of data

To represent data I used binary code in the form of a torus shape to represent 0's and a pill capsule shape to represent 1's. White and energetically vibrant colours were used to suggest the nature of photons.

3D virtual content representing binary data in transmission

The concept behind the materials on the gallery floor
The gallery floor space, between the towers, represented the terrain between the original shutter towers.

The materials used were:

• compost and gravel to represent the ground
• thirty six acrylic panels with felt contour lines simulating a contour map of the land between the shutter towers and suggesting that the towers were predominantly built on hilltops. The two centre rows, of six panels, contained markers.

Panels on floor, with some acting as markers (the ones with square symbols)

The concept behind the 2D virtual content on the gallery floor
The virtual content for the floor markers was predominantly a green 2D animations that suggested the green fields of England. The oscillating nature of the animation suggests the point of view of an imaginary photon looking down, as it transits between the towers. Two identical animations, one between the leftward and central tower, and another between the central and rightward tower can be viewed. Each of these animation is made up of six long narrow (identical) animations that run simultaneously, giving a striped appearance. The striped design enables the art viewer to still see the real ground underfoot, so they do not become disorientated, dizzy, or nauseous.

2D virtual content of the floor markers representing the lush green fields of England

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