To achieve maximum clarity a map should be designed from the very beginning with its final display medium in mind. There are numerous output formats for maps and various types of media on which they can be disseminated. Each has its own merits and its own limitations so there needs to be sound consideration and a valid reason for the choice that is made.
Things to consider are the map’s scale and resolution, colour mode (generally RGB for screen and CMYK for print), the size of paper or screen, the type of paper or screen; and interactivity and functionality options.
These considerations may lead to known rules, for example the minimum point size that can be applied to the map’s text in order to still be legible, or the lightest shade of a particular colour that can be perceived on a particular device. When setting such rules one may consider the optimal display or if the user base is varied then a lowest commonly used denominator may be preferred.
OS OnDemand – Ordnance Survey’s Open Geospatial Consortium (OGC) compliant web map service (WMS) delivers data over the internet.
These maps are designed for on-screen use so that means using colours from the RGB colour space. It also affects the choices made regarding fonts and symbols. We carefully selected fonts that are designed for the purpose of being viewed on-screen.
OS OnDemand contains lots of products, all viewable at various scale ranges. This means selecting line weights and font and symbol sizes so that they are legible at any given scale within the set viewable range.
Multiple products can be displayed at any one time so we also have to consider those products which will overlap each other. An example of this is where the user can display Integrated Transport Network Layer on top of OS MasterMap Tography Layer.
OS OnDemand is available to use in either a web browser or in a geographic information system (GIS). With this in mind the styles we chose for each product were tested thoroughly in various software packages and on different screen size.
Back to Cartographic design principles.