highlighting

Even without sophisticated WebGIS technology, it is possible to interact with maps on the Web.

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The first map combines a GIF image with an HTML image map. The map is an interface to other resources. Adding JavaScript to the mix, the combination is used to highlight that part of the Netherlands that the mouse pointer is over. This doesn't work in my Mozilla browser, by the way. Should really be implemented using CSS anyway...

the Netherlands
Map of the Netherlands

Your browser does not support Scalable Vector Graphics. If you install the Adobe SVG Viewer, or upgrade to an SVG-compatible web browser, you will be presented with an interactive map of the Netherlands.

sensitivity

Size is a very important aspect when defining hotspots. How small can a hotspot be to be distinguishable for a mouse pointer (technical limitations) or users (perceptual limitations)? This leads to the issue of sensitivity.

When a map feature is too small to be discernable, the hotspot should be enlarged. Should the distance between the border of the hotspot area and the map feature be fixed for each map feature? Should this distance be a percentage of the width of the map feature, where the width is measured perpendicular to the border of the hotspot area?

exclusiveness

Hotspot areas in an image map cannot overlap. Each pixel on the image map can be part of only one hotspot area. This is an important issue to realise when defining hotspots to map features.

For example, there is no straightforward solution to assign one hotspot for a country and another for the main capital of the country. The hotspot area for the map feature that represents the capital would overlap the hotspot area for the map feature that represents the country. Hotspot areas must be exclusive.

co-incidence

In the first map, the hotspot area does not co-incide with the highlighted area. Depending on the direction from which the map feature is approached, the region is highlighted or not.

responsiveness

Another drawback in the first map is that the first time the mouse pointer passes over a map feature it takes long before it is highlighted. The downloading time for the images is too long. The map does not respond timely to the user's behaviour. The interaction is a-synchronous.

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