Global Positioning System Reference
In-Depth Information
8.3.3 Positioning on a Map
If a position of an object or person is known from some sensing system, it can be
mapped. The physical sensing process will result in measurements and the
creation of values (or numbers) that can then be transformed by an algorithm into
coordinates according to the relevant reference frame. Sets of coordinates are then
added as new vectors that can be displayed if required (in the raster image). It can
be appreciated, therefore, that with each new set of measurements the information
space increases in size and usefulness. Not only can current positions be shown, if
time stamped, but past positions and tracks can also be displayed. Most
positioning systems that capture motion will store track-logs as sets of coordinates
with time-stamps. Future positions can also be inferred by using algorithms to
predict motion or improve accuracy by smoothing out sensing errors. (The
Epilogue contains details of the Kalman filter and Particle filter that are
commonly used.)
8.3.4 Geographical Information Systems (GIS)
Since the early 1980s the GIS industry has emerged, and very powerful software
applications have been written that depend on powerful and massive underlying
databases. ARC/INFO from ESRI was one of the first systems, but today there are
many (e.g., Oracle Spatial). Industry standardization groups, in particular the
Open Geospatial Consortium (OGC), have been established.
GIS can be used in a number of ways. A GIS desktop application may be used
by a trained expert to create customized maps, for example, the location of a
company's best customers, and be combined with a tracking system to show the
progress of a truck en route to them. It may be used as a tool, for example, to plan
optimum routes or to store historic information and be linked to other enterprise
systems. Sometimes a GIS may be invisible (i.e., the underlying information space
is used but no conventional map might be displayed). A reverse emergency call
service might use a GIS to work out what proactive calls and messages to generate
(see Section 4.5).
The term “distributed GIS” is used to differentiate between the original
single-user GIS that would be used on a single work station and the situation
today, where generally the components are not colocated. Enterprise GIS is used
within an organization and is usually distributed and has licensed mapping
content—an example is Microsoft's MapPoint. A Web 2.0 approach will (by
definition) be distributed and may serve an enterprise or the general public. The
content will be covered by a licensing agreement with the mapping owner but the
service might be free for personal use (with perhaps advertisements providing a
revenue stream to pay for the content). An exception is, however, the growing
open mapping movement where the mapped content is an “information common”
(see Section 3.3) and will be described in more detail in Section 8.7.
 
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