Developing Visual Navigation Skills - Window-to-Screen Ratio

Tacit visual navigation skills are acquired through continuous observation of the changing visual scene combined with immediate feedback.

The sketch  below is an actual scenario en route to Dammam, Saudi Arabia. It's a buoyed channel, 6 miles long and 3 miles wide, sometimes fishing boats are present. 

At 18 knots the transit along the 6-mile leg takes 20 minutes.

The typical inexperienced officer will focus almost solely upon the ECDIS with only occasional quick glances out the window.

Aside from the separate issue of maintaining a proper lookout by all available means, inexperienced officers fail to appreciate how tacit skills are acquired.

The Hidden Value of the Instruments

The hidden value of the instruments  is that they provide rapid, high-quality feedback which enables  bridge watch officers to improve and gain confidence in their visual perception skills much more quickly.

The Window-to-Screen Ratio

Rapid perceptual learning  requires that the window-to-screen ratio be reversed. ECDIS and ARPA do not require uninterrupted fixation in order to serve as an effective cross-check to visual observation. The reason more experienced watch officers and pilots use visual observation as the primary basis, with the screens serving mainly as a cross-check, is that with practice, the visual scene becomes a rich, continuously changing source of information.

Continuous Observation and Tacit Skill

The watch officer should feel free to check the instruments as often as required to cross-check and calibrate out-the-window observations, but it should be understood that repeated interruptions  in continuous visual observation are not without cost. Gaining skill in visual perception requires watching the visual scene change continuously over time, not merely making quick glances out the window.