1.1.6. Scale
The layout principles for paper maps also apply to web maps. There are a few peculiarities that have to be taken into account.
It is impossible to predict the final scale at which a map will be displayed on the screen, since the actual size of the map depends on the resolution of the monitor. Therefore, one should avoid indicating the scale in numbers (e.g. 1:25'000) and use a scale bar or a Cartesian grid instead. (Räber et al. 2003)
We picked some maps out of the Internet (status quo: 2006) which include
the map's scale.
The first map indicates the scale in
numbers what is not ideal. In fact, the scale number adapts itself correctly
to
the zoom level the user has chosen, but as you can see the chosen scale is a
complicated number. Calculating a distance is not easy with such a scale factor.
All the other maps indicate their scale using a scale bar or a grid
whose appearance changes from application to application.
Scale indicated with divided scale bar (Bundesamt für Umwelt (BAFU)) | Scale bar indicated in meters and miles (Map content (c) 2007 by MapQuest, Inc and NavTeq. Used with permission) (MapQuest) |
Scale indicated with grid (Google Earth) | Scale bar (Stadt Jena) |