CartoBlog

In February of 1996, R.R. Donnelly & Sons, a publishing company founded in 1960, turned their gas-station-map division MapQuest into the first online consumer mapping web site. Over a decade later MapQuest.com serves up over 1.1 billion maps and routes each month. Of course MapQuest is not alone. In 1998, Microsoft launched the Expedia.com travel site, which included an address and directions finder map (full disclosure: I designed that original Expedia map). Eventually ESRI, Yahoo, Google, and a multitude of others jumped into the online map game. MapQuest was bought by AOL and while still popular is not the dominant mapping site any more. Microsoft’s Expedia maps morphed into MSN Maps and then into it’s latest incarnation called Live Maps.

A screen shot of the original Microsoft Expedia Maps, which was limited to the original “web-safe” palette of colors and a fixed size designed to fit within the size limits of 800×600 and to save on bandwidth.

The first online maps of MapQuest and Microsoft were the web-based extension of a new trend in CD-ROM maps. Products like Microsoft’s Encarta Interactive World Atlas (neé Microsoft Virtual Globe) and Streets & Trips, Travroute’s Door-to-Door, and DeLorme’s Street Atlas gave us revolutionary technology to view maps from any zoom level, while panning endlessly. Not to mention the, until then, unheard of ability to generate driving directions between any 2 addresses anywhere in the country. These “dynamic maps” on CD-ROM and the web brought maps out of library drawers and dusty boxes of old National Geographic Magazines. All of a sudden anyone with a computer had access to maps of every state, neighborhood, and street in the U.S. Now it is safe to say that most people wouldn’t go anywhere unfamiliar without first consulting an online mapping service for directions.

A New Cartographic Medium

With infinite combinations of panning and zooming, dynamic map systems present a unique set of challenges to cartographers. Traditional static map design, for either print or screen display, allow the specific map with a set area and set scale to be carefully crafted. Dynamic maps have to be designed with the entire data scope in mind, from urban to rural areas, and from small scale to large. The maps are rendered en-mass from a digital map library, using a set of symbology rules for the design elements. That gives the designer little control over the look of any individual map view, requiring careful planning, visual sampling, and a lot of compromises.

By definition, dynamic map systems are for on-screen display. They can can of course be printed, but the primary display medium is a computer monitor. Dynamic maps suffer the same limitations as any on-screen map: low resolution, limited size, inconsistent color display, and performance considerations. There are design techniques that can be employed to overcome some of the restrictions of digital map display, but dynamic systems often add additional challenges, usually tied to technical limitations of the map drawing engine.

Visual niceties that can be employed with static digital maps such as anti-aliasing, gradients, and text effects are simple and effective using tools like Photoshop and Illustrator but these same features can significantly slow down the back-end application performance, and these effects are therefore often not available. A slow and unresponsive dynamic map interferes with the exploration of the data being presented, and this will outweigh any improvements in visual appeal that are slowing the map down. In general the basic principals of good map design apply: clarity, hierarchy, color selection, etc. However it may take more effort to achieve these in a dynamic system.

For static maps, data can be carefully selected and manually simplified to achieve an optimal density of features at the maps specific scale. At any given scale (i.e. zoom level), Dynamic maps can be panned to any portion of the mapped area (the entire world in many cases), render all areas with the same set of selected data. So by displaying street level data at an intermediate zoom level, a view of the New York metropolitan area may be a crowded mess while Nevada only shows a few roads at the same scale. On a world map, showing all towns over 1,000 people in Japan might be extremely cluttered at a certain scale, but you may see no places of that size at all in certain areas of Africa at the same scale. For every scale the data displayed must be balanced, and usually with some compromises, between showing too much in dense regions and too little in rural areas.

One way to minimize the effects of the data density compromises, is to carefully craft the symbology at intermediate zoom levels where these problems appear most often. Well designed dynamic map systems allow for symbology changes at various zoom levels.

One of the graphic limitations of low-resolution mapping is that there is very little subtlety when it comes to line weights. Even a 1-pixel line looks heavy and dominating on a map, especially when combined with many others, as in a detailed road map. Giving the line a color that is close in value to the background color can create an illusion of a thinner line. Likewise, bordering a polygon on the map with a line that is just slightly darker than the fill color adds just enough of an edge to allow the fill color to be very close in value to the background, allowing the element to recede visually. Sending some objects to the visual background is very useful for many of the low-resolution issues, and works equally well to minimize the dominance of type and symbols. Subtle color palettes can be problematic due to difference in end-user monitors, and the way different operating systems render color. Designs should be previewed, when possible, on different monitors as well as various browsers.

Custom Dynamic Maps

While most cartographers don’t have the opportunity to design and create new online mapping service from scratch, there are now a number of ways to create custom dynamic maps for clients and other projects. Google’s Virtual Earth allows a broad range of customizations from point and line features to replacing the background images on the virtual globe. Likewise Google Maps online and Microsoft’s Live Maps have a limited stock tool set for adding customizations. A skillful programmer can create “mashups” and hacks to take these customizations further.

ESRI, the maker of the industry standard GIS software, has a very robust offering called ArcWeb Services, which allows for a broad range of customizations and because of the GIS backbone, even opens up possibilities for customization of the underlying data.

It is only a matter of time before these packages evolve into rich, full-fledged mapping applications allowing cartographers to quickly produce maps that go beyond static images and give their readers and clients infinite ways of looking at information.