Processing Digital Maps - Programming GPS and OpenStreetMap Applications with Java - page 80

recorded traces in the small application MovingObjects in the preced-
ing chapter. 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 (com-
pany's) map specications. In given intervals, dierent 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 cre-
ating 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.