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Weblog Entry

Mapping on the Web

March 31, 2003

I’m currently involved in a project that deals with large–format maps targetted towards high–resolution HP plotters. The finished maps are around 4 feet on both sides. Somehow, these incredibly huge pieces of paper have to be neatly represented on a low–resolution 15 inch monitor.

Unless you’re running a custom CGI setup and have access to greatly–detailed vector maps, ala MapQuest, the job of converting a static map to something that’s actually usable on the web is enough to make you lose sleep.

First problem: text. At 11 or 12 points, text on the printed map is perfectly legible. When you start shrinking it down even a bit you begin losing that, and when you shrink it down a lot, it’s hopeless. Second problem: detail. Land is complicated and intricate, and maps tend to reflect this. Third problem: file size. The detail you need to capture will choke most image compression methods, despite their best efforts to reduce it.

In a perfect world every client that requires maps would be able to offer vector source to work from, and flexibility that allows you to use a number of options to present the material, ranging from SVG to PDF. If you live in this perfect world, please, send me a post card.

The rest of us are stuck with reality, however, and we have to make the best of a bad situation. This involves multiple versions of the same map for previews, large format views, and detailed views. Possibly the inclusion of a PDF or two for printing.

In this particular case, the client recognized the problem at the onset and with a detailed guide from me, were able to ask their cartographer to generate custom maps that we’d be able to work with. The 6000–odd pixel wide JPGs I ended up receiving were still way too large, so they had to be cut back further.

The solution was to present a tiny, reduced version as a preview, which makes no attempt to represent any detail. The preview is clickable, and loads a 2000 pixel wide JPG in a new browser window that an end user may scroll across. As well, 8”x11” PDFs are offered for print usage, and since they do need to target their high–end users, HP–plotter specific high–resolution maps are linked.

The client understands that at 500 pixels, the preview map in no way represents the end map other than to serve as a quick overview, almost an icon. The end user is specifically told that a few larger versions exist and are easily accessible, and the solution appears to be working.

These type of hacks are regrettable, but in many cases necessary. Custom scripts are not available in every budget, and in many cases the source material is less than optimal for the end use. But a bit of creative thinking and adaptability can come up with a solution that works.

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