Those familiar with the Harry Potter series may be familiar with the Marauder's Map, a map that allows the holder to see where people are at any given time. It displays a person as a set of footprints with a label next to them. The footprints appear and then fade as a person walks along.

For all intents and purposes, this is a map that changes over time. It's pretty cool, and I would, of course, love to have one in a story of mine.

The only restriction is that the map cannot be a screen. It has to be like a classic map: A scroll of material that can be carried around. I know there are advanced screens that can do that, but I'm not allowing them.

The map needs to change in some way. I suppose that attaching a microprocessor and a receiver could take in information real-time, and then provide control to the map, or the map could change in a cyclical fashion. Either way, the display needs to change.

Can this be done? Let's say that the technology level is circa 2000.

  • $\begingroup$ Damn it man, you'll outdo the rest of us if you're not careful :) I suspect, however, that the answer is at least not easily. Should this be science-based? $\endgroup$ – ArtOfCode Jun 10 '15 at 21:03
  • $\begingroup$ @ArtOfCode Yep, but not hard-science. I'll make the change. $\endgroup$ – HDE 226868 Jun 10 '15 at 21:04
  • $\begingroup$ On the blurry line between restricted and not, what about flexible screens? dailymail.co.uk/sciencetech/article-2814136/… $\endgroup$ – Cort Ammon Jun 10 '15 at 21:30
  • $\begingroup$ @CortAmmon I would say no to that. It's still based on a classic screen. $\endgroup$ – HDE 226868 Jun 10 '15 at 21:32
  • $\begingroup$ @CortAmmon It's also post-2000 technology, nearly all flexible displays are. $\endgroup$ – Samuel Jun 10 '15 at 21:33

A resistor network and thermochromic ink.

The map of the building stays the same, while the footsteps are the only part that needs to change. The footsteps show up quickly and then fade over time.

This can be achieved with a heater grid, made of multiplexed resistors (as very thin and fine grid of flat nichrome wires), and thermochromic ink.

More likely if this were developed at the turn of the century, it would use pre-defined name labels and footsteps graphics (similar to watch LCDs). The resolution to display arbitrary names or whole maps would not be something that a microcontroller of the day could have implemented.

The light to dark thermochromic ink can been seen in action on some Rorschach masks. It also demonstrates that relatively little heat is required for operation and that fading can occur rather quickly.

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What you're talking about is, variously, smart paper, or electronic paper, and various developers are hard at work.

If you allow your map to be rolled up, it can be done today, although incorporating both power supply and processor is a challenge. Presumably, since such a map requires ambient light to read, some sort of solar cell would be used.

Much harder is making a map that folds.

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I don't think it fits the rolling part, but one could think of a seemingly cool device. You need:

  • A thin yet rigid board,
  • A magnetic pawn,
  • A magnet-equipped armed controled by a microcontroller,
  • Some more fancy communication tools.

You get the idea, you place your pawn on your board with the map of Hogwart drawn on it. You use the two magnets to move your pawn on the map side (upper). Below, you have a basic arm which can be moved in 2D below the map and with two positions: stuck to the board (below) or separated.

When the arm is stuck, a pawn that would be situated at the opposite side, would move along the arm. When it gets separated, the pawn stays put.

Now, what can you display? Well basic thing, you get a loop to show some scene, and the microcontroller essentially repeats it over and over again. For more advanced, you might want to couple it to cameras and/or sensors located around the castle to detect some people moving into the corridors.

Getting the name of the people without display, would need to have special pawns (one for each person) and face recognition.

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    $\begingroup$ Ah, if I understand it right, this might use the same sorts of techniques employed in the 1984 remake of the Mechanical Turk (or other chess-playing toys of the 80s and 90s), basic cellular phone technology of the day, and perhaps some repurposed etch-a-sketches... So long as the board is ferromagnetic, the pieces would stick to it by default, and using some small servo motors and an electromagnet, you can choose when to pull the pieces around in relation to one another. That's a pretty good solution! $\endgroup$ – Ayelis Jun 11 '15 at 9:42
  • $\begingroup$ I don't know the examples you refer to, but yes, you apparently understood my concept. And yes, I find it good as well, thanks for the comment. These days, any DIY/Arduino/MCU hobbyist could make such a map. $\endgroup$ – clem steredenn Jun 11 '15 at 10:14

Depending on your definition of screens it would be possible to make a wearable (electronic cloth piece).

With tiny components weaved in to it to make a diode, this diode can be made of materials that makes it glow (Light emitting diode) and then very small, like millions beside each other - this is possible with today's technology.

The problems here is that someone decided to make screens the same way, many of you are properly watching this page on an LED screen. Either on the phone or a computer.

So depending on your definition, this is a viable option, the problem here is the size of the GPRS network and GPS antenna tends to be quite large. And batteries also seems to take a bit of space, but a li-ion pack can be made thin and the size of a paper, and also li-ion is foldable.

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