Overview of Processing Digital Maps
(book chp 7.2)
This Tutorial Trail can be seen as an excursion from the ROAF into digital maps and navigable networks, which are needed to explore any area on the globe with a real object. The Trail will guide the reader to process OSM deliveries to significantly reduce map data and how to process this data into a cartographic part, a network part, and an administrative part from one map source.
The Life Cycle of a Digital Map
A complete life cycle of a digital map from collecting map data to forming a dedicated product can be outlined in five steps:
1. Collecting map details
The first step to create a digital map is the collection of geometry data in the field, as demonstrated with the recorded traces in the small application MovingObjects. The second major building block is the administration, which describes the political structure of a country and can hardly be determined in the field.
2. Creating maps
After collecting individual traces, field workers can make use of graphical front ends for analysis and modification. The traces are simplified and validated against other sources, like satellite pictures, elevation contours, and existing map data. The geometry is then verified and the points are drastically reduced and labeled with features and attributes describing the real world.
Making digital maps is a never-ending process as the world changes constantly. Accordingly, each digital mapping organization has one main server to hold the map. Field workers "check out" the area of their responsibility, add new content, remove old content, or modify the data, before transferring data back into the live map.
3. Delivering maps
The main map server (or mainframe) runs around the clock to validate the incoming data and to enforce the (company's) map specifications. In given intervals, different parts of the map are extracted from the live map into predefined map coverage and formats. Afterward maps can be enriched with additional (third party) data.
4. Processing maps
Digital maps are gigantic chunks of geocoded data and the mapping company's live maps are designed to hold almost any data collected by field teams. It is important to understand that digital map deliveries are not customized for applications like navigation systems or online maps. It is necessary to process the map deliveries to fit various applications.
This process from map deliveries to a physical storage format (PSF) is usually referred to as map compilation. Map compilers clip data, reorganize data for fast access with low memory consumption, and separate data for rendering, navigation, etc. Each map compiler is build to fit the requirements of the mapping application. While creating maps is a manual effort of many people, processing maps is automated.
5. Using maps
After the vendor of a navigation system, for example, has created a PSF for his system, the system can "read" the map on a physical storage for navigation. A navigation system is completely useless without a digital map and the system can only work with details (features, attributes) available on the map.
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