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Information Rich Display Design

Since some time I loaned a book from the library: Edward Tufte’s “Beautiful evidence”. It still awaits me reading it. In the meantime I stumbled over a paper which integrates graphic design rules into the design of process displays used in plants. Plants means all different kinds of plants, ranging from central operating units of oil platforms, to wind energy parks to nuclear power plants. These structures have in common that they have a room from which their process is centrally monitored and coordinated. Mostly it is done nowadays via displays presented on monitors. The information presented on the monitor is specifically designed for that purpose. What you see at once on the screen is called a display, process display if it is showing information about the plant.

Purpose of the displays is to condense interconnected information on a small area. Usually there are more than hundred displays overall presenting information about the plant’s processes. Their difficult purpose is to support the operator in their manifold tasks. During normal operation, meaning monitoring of the process without any noteworthy occurrences, the operator’s task is comparable to that of an analyst. The operator examines the situation and attempts to get knowledge by comparing the current situation with similar patterns from similar situations. It is a slowly paced task requiring rather overview information. If something goes wrong the operator’s task switches to that of a firefighter. Then they need specific easy to pick-up information. The different tasks can be associated with the mental processing levels defined by Rasmussen: skills, rules (task of a fire fighter) and knowledge (task as analyst).

The difficult task of the display designer is to provide the operator with suitable displays supporting them in all their tasks. The traditional process display design has the following disadvantages:

  • different information need of the operator: – in normal situations better to present the information condensed but in stressful situations only the information needed, as information processing is narrowed only a limited amount is taken in – information on the display that does not belong to the task needs to be avoided
  • Problem of interconnected information that is visualised in small parts is the keyhole effect (think of the more than 100 displays overall to show the process of the plant). It means only a part of the process information is displayed at once. Mental effort is required to stitch the information correctly together.
  • Thick lines and vibrant colours are commonly used to show static information, while the valuable dynamic information is “hidden” in this cluttered design
  • A typical VDU process control display format consists of typically 10-40 valuable dynamic data points, compared with good design within other areas such as medicine, statistics and cartography this is low

The proposed information rich display design guide applies rules from other areas that must deal with huge amounts of information like cartography and statistics. The disadvantages listed above point already to one improvement – it seems possible to integrate more information relevant data into the displays without overloading the displays. If more information can be presented at once the “keyhole effect” of seeing only a fraction of the process could be reduced and also the need for navigation.

The proposed principle is called Dull Display Principle, simply meaning to weigh information by colour (I would see is as part of the “Gestalt Laws”). Usually a display contains static information which help to identify the process parts shown. That is connecting lines representing pipes or electrical connections and e.g. outlines of a pump or water storage tank. According to the Dull Display approach this static information is presented in different shades of grey. In contrast dynamic information which needs urgent action is presented in bright saturated colours like red and yellow. So different visual layers are created which emphasise the urgent information and make it easy identifiable even if there are many elements on the display. Below you can see an example. The left Figure shows a traditional process display design. The right Figure one designed following IRD. The colour in the right Figure represents the medium (blue – water, dark green – oil and green – gas). Left traditional process display Right process display in IRD design

Further the IRD approach aims to integrate the knowledge need of the operators. Whereas it is known that experienced operators monitor parameters over time using trend plots (diagrams with past values of a parameter) instead of reading exact process parameters, they are so far kept on separate displays. The proposed design approach foresees to integrate mini trends in the process displays. A single value only shows the current state of the parameter, you have to watch carefully to recognise a trend, if the parameter is increasing or decreasing, if it changes at all. A trend, in contrast, easily shows the direction of change in the position of the line. The Figure below shows such a mini trend.

Mini trend for process displaysSources:

Alf Ove Braseth, Oystein Veland and Robin Welch (2004). “Information Rich Display Design”. Forth American Nuclear Society International Topical Meeting on Nuclear Plant Instrumentation, Controls and Human-Machine Interface Technologies (NPIC&HMIT 2004), Columbus, Ohio, September, 2004

Alf Ove Brasth, Ville Nurmilaukas and Jari Laarni (2009). “Realizing the information rich design for the LOVIISA Nuclear Power Plant”. Sixth American Nuclear Society International Topical Meeting on Nuclear Plant Instrumentation, Control, and Human-Machine Interface Technologies NPIC&HMIT 2009, Knoxville, Tennessee, April 5-9, 2009, on CD-ROM, American Nuclear Society, LaGrange Park, IL (2009)

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