Cartographic generalization

In the generalization of the map content is simplified, so the readability and comprehensibility remains a map. This is necessary if small map scales the realistic and full reproduction is no longer possible. Generalization scale images are replaced by simplified images, symbols or signatures. Information is selected, summarized and important benefit of the unimportant illustrated preferred.

For a realistic picture of the contents of a map would have to be photographically reduced to illegibility. Additional information such as place names cover behind map content. Clearly legible maps characters are far greater than the scaling down of the object depicted. They compete with neighboring therefore map drawing and map contents to the available space.

The generalization provides a balance between these competing demands for realism, completeness, legibility, diversity of information and space requirements.

It is therefore a key differentiator of the map of a photographic image, such as an aerial photo or orthophoto.

Process of generalization

In the generalization of the map information several processes at the same time and if necessary applied to the same map object.

By selecting irrelevant information is excluded from the display and make room for what's important. Which is "important", depends on the type of card. In general maps and road maps for instance only the significant and wide streets are shown. In a topographical map großmaßstäbigen dirt roads are still selected for display.

The simplification of the presentation can begin at the site survey by the topographers. Small Gebäudeversprünge are not included in the survey or smoothed when drawing the maps. In serpentine meanderings and the curves for the presentation are smoothed and at very small scales they are indicated symbolically.

Summarizing especially similar representation creates space and clarity. Typical is the grouping of houses. In the topographical map individual houses are represented in scale 1:25.000 yet. Already in the following scale of 1:50,000 they are combined to house groups. Closed built-up areas are represented by surface signature.

By classifying the map image is kept simple. The classification results in category formation, thereby helping to limit the scope of the character set of the map makes sense. Thus, the topographic map required only sign of " conifer " and " deciduous tree " instead of for each tree species. With the classification of cities as " seat of government " by underlining the name writing the card receives additional information.

The assessment is used to emphasis or highlighting an object. This may be an additional information, such as a symbol " worth seeing object" for a historic building, or bold a name. The cartographic exemption of a card character eg by a highlighting edge can also serve the evaluation.

Enlarging in comparison to the full-scale representation is essential to preserve the readability of the card. The most common application is the widening of the use of signatures for traffic routes.

The targeted repression is usually required as a result of enlargement. Through the widened road signature the adjacent houses are displaced from their geometrically correct map location. A prime example of the Generalisierungsaufgabe to regulate the displacement provides the Middle Rhine Valley. Here are both sides of the river railway lines, highways and local roads that need to be shown in small-scale maps by signature. The cartographer must consider whether the Rhine is shown narrower or smaller Hunsrück. It will inevitably lead to contradictions in the small-scale topographic maps: a trigonometric point must be played in the correct position in the map, so you can read its coordinates. Due to the space requirements of road and railway signatures he seems to be middle of the road on the map. But in nature it is on the displaced in the top of a map Rheinhöhe.

Occasion and time of the generalization

The main cartographic elements that make a generalization required, the scale, the map theme and the manufacturing process.

As a limited scale is called the generalization when the scale of the map does not permit a detailed reproduction because the space is not sufficient.

In the theme -related generalization of the type displayed map information requires a simplification and summary. Thematic maps require an appropriate treatment of the subject information to be displayed and usually use simplified base maps that are derived, for example, by generalizing from topographic maps. While standardized procedures and agreed cards signs used in topographic maps and atlases of generalization in many areas, often with comprehensive thematic data of the generalization process. So must a new decision and the nature and extent of the character set used to be redefined depending on the topic and the type of statement of fact. The time of data collection can play a significant role in the generalization, for example, if the facts be displayed permanently change, but the card should remain current for a longer period.

As due to the process is called the Generalisierungsvorgang when external conditions force to simplifications or restrictions on the collection and processing of cartographic information. Which may be, for example cost aspects, the basis of which an estimate rather than an accurate count is made. The automated presentation of the card contents on low-resolution graphics displays requires a process-related generalization.

The generalization process accompanies the card production from the initial data acquisition to prepare the card playback on a master or other display device. The generalization in the data acquisition is referred to as Erfassungsgeneralisierung. Is generalized between different models, one speaks of model generalization. The cartographic generalization, has especially compliance with the minimum dimensions when creating a cartographic model to the target. Especially in the cartographic generalization, the demand for geometric accuracy is restored in favor of readability.

Automating the generalization of digital maps

Generalization is a process of weighing and requires creative skills to design a card with an attractive and harmonious appearance. Thematic mapping partially innovative approaches are necessary. In contrast, the automation of the generalization process requires solid algorithms. The aforementioned Generalisierungsvorgänge are therefore tested for their suitability for automation and classified. While the above broad representation of a road is easily automated using signatures, includes positioning of place names too difficult to automated processes. The rapid growth of digital map applications but requires short-term automated processes. Here are pragmatic and simple approaches entirely appropriate to the map image at low resolution screens to improve in the short term, such as in navigation systems.

Work is in progress in cartography reinforced at the automatic generalization ( ADV project).