In many ways the single most debilitating factor of an electronic chart display system is the limited screen real estate. You can never really see the whole chart so instead you have a keyhole view. Like looking at a room through the keyhole you can only ever see a part of it. To understand what the room is really like you need to keep looking around and build up a mental picture to supplement the limited bit you can actually see. In all other ways an electronic chart is probably better than a paper one. Updating is quicker and more accurate, so it positioning, laying off courses and the rest of it. Ah, thinking about it, you can operate a paper chart by candlelight so maybe that is the other plus for the paper chart.
With Nuno we have done a bunch of things to try and compensate for the lack of screen size. To begin with we try and avoid dislocating affordances. An affordance is something which by its appearance invites you to do something with it. Like a door handle or in the computer world a button on the screen. It is a very important principle in User Interface design. When you look at a computer program and you want to make it do something the first thing you will do is look for affordances – something you can press, drag, select or whatever. A dislocating affordance is one which suddenly makes the whole screen change, like a control which make the chart view jump. It is a bit like spying through the keyhole, closing your eye, changing position and then looking again. You can see a different bit of the room but you don’t really know how it joins up to the first bit you were looking at. Much better is to maintain a smooth transition from one view to the other using panning and zooming to maintain a sense of continuity.
Overall we have tried to use as much of the screen as possible to display chart. There are no fixed panes that reserve a chunk of the screen. You can arrange a pane like this if you want to but it is not imposed on you. The control bar at the top can be made small and everything else is given over to the chart. Many of the affordances are arranged around the screen in fixed positions so that you will always know where to find them but they become translucent when not being used. Sure they obscure the chart a little bit but you can still see chart and we think the more chart you can see the better.
With vector charts your view is not onto something like a bounded paper chart but more like a view onto an enormous cylinder where the whole world is projected. If you keep panning right you will eventually come back to where you started. This means that however big the screen is that you will still need to pan and zoom. I should clarify at this point that I am not simply talking about the physical dimensions of the screen but also the number of pixels or dots that are used to make the image. To display an image of a paper chart on a screen at about the same size as the original you need about 100 dots per inch (dpi). Less than this and the image will be blurred. More than this and the image will sharped up and be clearer to look at. Traditionally charts are printed with at least 600 dpi so to get a screen image as well defined as that on the paper is not really possible with current screens. 100 dpi is reasonable a compromise.
So what is the best size for a screen? Well you need to be able to see it all without having to walk around. In fact if you could reach across to any part of it then that would be good. Maybe this problem is already solved. Maybe a paper chart has evolved to be just the right size. Maybe in 200 years of making charts we have actually come up with something that is just the right size for the job. Now the standard size for a full paper chart is a half double elephant. This is not, as you might think, the same as a single elephant. The elephant folio is up to 23 inches tall whereas a double elephant is 50 inches. So the paper chart, at around 25 x 40 inches is in fact a half double elephant.
A screen this size would need to 5,000 pixels wide. At the moment the best mainstream video standard is dual channel DVI which supports up to 2,560 x 1,600. So four of these lashed together could look pretty good. A company called Cinemassive (great name) make a set of monitors like this. EyeVis have some pretty good single screens 64” 4096 by 2160 – not quite enough pixels and a rather eye watering price. However you look at it though we are nearly there.
One problem with such a big screen would be that your poor old mouse is going to run out of steam. You would need a mouse mat four times bigger unless you could manage to move the mouse four times more precisely. But imagine that you had the screen set up just like a chart table – wouldn’t you just want to reach out and touch it? Multi-touch technology is really starting to gain pace now. Once you get to grips with an iPad you soon find it is a great way of doing things (although pretty hopeless if you have gloves on I recently discovered). The Microsoft Surface is one of the pioneers here. And it is already a table. Sadly for now it doesn’t have enough pixels but it is still showing a really good way forward.
So a screen the size of a chart table is not going to suit every vessel but we are close to a practical system. In fact my company are looking at a project to prototype a full sized electronic chart table along these lines. It is quite feasible that screens will progressively get lighter and cheaper and maybe you could even roll it up. Bigger is better?