Network-friendly Tube & Bus Maps
(Turn up your volume by the way - Chopin's excellent piano waltz "Grande Valse Brillante Op.18" is playing in the background.)
Ever been frustrated by the inordinate amount of time it takes to browse around the tube maps on the official London Underground website? I'm not surprised if you have - because I certainly have - and I'm sure I'm not alone. For example - the standard tubemap is a 1.4 MegaByte PDF file. Now - I have high-speed ADSL at home - so this only takes a few seconds to fire up in my browser - but I do feel really sorry for those folks on dial-up modems! And just imagine if you were trying to view these maps on a PDA over GPRS - not only would it take ages - but it would probably cost you a fortune too!
So - you know where this is leading to: I've been experimenting with techniques to shrink large documents - without losing the fidelity - because you definitely need that with maps - it isn't much fun zooming into a map and losing the definition to the point that it becomes unreadable! I suppose that's why it's so common for organisations to publish maps as PDF files - because you don't lose the definition - the more you zoom into the map - the more you are likely to get a good definition of what's on the map. So - I guess it's always going to be a trade-off between quality and file size.
So - I discovered a remarkable bit of technology that was apparently invented at NASA sometime back for encoding large images suitable for beaming from satellites and rockets back to Houston. This technology is marketed by a company called LizardTech and amongst several things they produce - there is this thing called DocRocket - which comes in two parts: 1) an encoder and 2) a viewer.
The kind people at mobile company O2 (who have been dealing with LizardTech) were supportive of my experiment - and they kindly loaned me an evaluation copy of the encoder. But what about the viewer I thought to myself? Well it turns out that the viewer is free - and best of all - it installs as a web-browser plug-in - just like Adobe Acrobat Reader, Macromedia Flash Player etc.
So - what I did was download all the official tube maps from the official London Underground website maps page- and all the official bus maps from the Transport for London website bus maps page. They were all fairly large PDF files - and I encoded them all using the DocRocket encoder. The encoder produces "DjVu" files - which, if you have the DocRocket viewer plugin installed in your browser, will automatically be recognised by your browser.
Well - I must admit - I was very impressed! The things I was particularly keen on understanding was the magnitude of the trade-off between quality and file size. Most of you reading this for the first time probably don't have the DocRocket DjVu browser plugin - so here is a "taster" of the sort of thing that I was impressed with regarding quality of the encoded maps:
I took the standard tube map PDF file and zoomed into it to 300% around the area of Hammersmith station. I also took the same full-size map - converted it into a GIF - and then zoomed into it to 300% around the same area. And I did the same with the DocRocket viewer looking at a DocRocket encoded version of the same map. In each case - I took a screen capture of the image and reproduce them below so that you can compare the quality of the images:
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300% Zoom on the PDF version
of the tube map: |
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300% Zoom on a GIF version
of the tube map: |
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300% Zoom on a DocRocket
version of the tube map: |
So - you can see that although the image quality of the DocRocket version is slightly inferior - it's still very usable - and actually quite remarkable considering it's zoomed in 300% on the tube map. Just look at the GIF version! Practically useless at this zoom level! (And actually useless at the 100% size - due to the tube map being packed with so much detail - it's just not possible to read the map without zooming in.)
So -the 64,000 Euro question is: "just how much is the DocRocket quality-compromise worth when compared to PDF?" Well - this is where it gets interesting! If you have gotten this far - then you need to be able to judge for yourself: you can download the DocRocket viewer free of charge from their download page - trust me - there are no pesky forms to fill in and no registration codes etc. the installation is very straightforward.
And here is the result. (Be sure to have installed the free
DocRocket browser plugin from the LizardTech website before viewing!)
When you have installed the DocRocket plugin - try the comparison for yourself! Try clicking on the link to the PDF version of the maps - these will bring up the maps from the London Underground or Transport for London's (TfL) official websites. Try panning and zooming in and out of these maps. And then try the same with the DocRocket versions. Take care to notice how much less time you have to wait for the map to appear in your browser - and when you pan and zoom - ask yourself whether you could live with the quality of the map. In particular - notice how when you zoom into the DocRocket version of the maps - right up to say 1500% - you don't get the same "noise" (chunky pixellations) that you get when you zoom into GIFs at that magnification.
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Standard Tube Map |
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Click
here to view it Click here to view it |
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That's a reduction in file size
to under 1/16th of the PDF!
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Tube Access Guide |
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Click
here to view it Click here to view
it |
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That's a reduction in file size
to under 1/4 of the PDF!
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Tube Access Guide (Index) |
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Click
here to view it Click here to view
it |
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That's a reduction in file size
to under 1/6th of the PDF!
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Large Print Map |
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Click
here to view it Click here to view
it |
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That's a reduction in file size
to under 1/4 of the PDF!
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Large Print Map (Index) |
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Click
here to view it Click here to view
it |
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That's only nearly half the size.
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London Connections |
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Click
here to view it Click here to view it |
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That's less than a third of the
PDF.
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Large Black & White |
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Click
here to view it Click here to view it |
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That's a reduction in file size
to under 1/5th of the PDF!
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London Buses - Streetmap of Central Zone |
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Click
here to view it Click here to view it |
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Not much of a reduction in size.
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London Buses - Spider Map of Bank
Area
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Click
here to view it Click here to view it |
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That's a reduction in file to
nearly half of the PDF!
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London Buses - Spider Map of Hammersmith
Area
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Click
here to view it Click here to view it |
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That's a reduction in file size
to nearly 1/4 of the PDF!
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So - what do you think? Are the maps practical and useable?
(PocketPC users: the folks at LizardTech have a PocketPC version of the browser plugin I think.)
Go to my blog to leave comments/thoughts etc.