Na przykładzie planów miast zaprezentowano związek wartościowej struktury graficznej dokumentu elektronicznego z poziomami czytania mapy. Omówiono cechy, jakimi powinien charakteryzować się właściwie zredagowany plan miasta: logicznie ułożone poziomy czytania oraz jasno określoną hierarchię elementów treści podporządkowaną zasadniczej funkcji tego typu map.
Development of computer science, availability of equipment and easier to use computer software significantly altered the process of map preparation. Most graphic programs and GIS used in map preparation make it possible to create databases which have layer structure. Therefore one can ask to what extent the layer structure of a computer-elaborated map connects to its reading levels which are linked to the perception sequence of map's components, or their groups. To answer this question, the authors analyze the editing process of city plans, which are one of the most common types of maps. In most cases map components have various significance, depending on their importance to the reader. To facilitate map's perception, its contents is divided into various levels of reading, which arrange the perception sequence of its components. This sequence depends on sign's hierarchy of visual importance and how it is contrasted against the background. the highest level of reading is composed of signs, which are most graphically aggressive, so that they can be perceived first. Consistently, lower levels which are to be read as secondary, are composed of signs of lesser visual importance. As a result, the appears a sense of components being placed on different visual levels. On the included figures, which show a plan of a city center, different layers of electronic document have been organized to show separate reading levels: - streets and street names (fig. 1), becouse the main objective is to show ways and directions; - thematic contents - point symbols, names (except street names), public transportation, railways (fig. 2); rearing of the significance of line and point symbols on a city plan should be intuitive, and their location perceived quickly; names of districts, parks, buildings, etc. should use a visibly different font and color from street names; they should not obstruct streets or street names; - areas - background, built-up area, greens (fig. 3); areal symbols set a background to other components, therefore they should be in toned down colors A ready to print city plan, containing all of the above layers is presented in fig. 4 An average reader does not have to guess the assumptions of map,s editors. Quite the opposite, a map should be edited to enable the reader to intuitively perceive the meaning of symbols and see the cartographer's intention. Therefore it is vital to establish a correct hierarchy of contents and assign a proper visual importance to its components, to make them perceived on appropriate levels of reading.