Geography Reference
In-Depth Information
example of the town boundaries, it's not beyond imagination that a process can be defined
to analyze an aerial image and determine if boundaries need to be removed.
Most often, however, automatic editing is used to perform tasks such as drift correction or
height and contour changes due to earth movement.
Transformation Tasks
As mentioned in the discussion of manual data input, when obtaining data for incorporation
into a GIS, the data will rarely be in a format suitable for inclusion in the system.
Making the data usable may involve something as simple as a coordinate transform, or
something as complex as combining multiple datasets based on common attributes and
more. Transformation processes can and often do seriously affect the overall data quality,
and many systems can end up with a lot of deeply rooted problems caused by mistakes
when transforming data.
In the U.K., these processes are almost always seen when working with latitude and
longitude coordinates, as nearly all the data supplied by U.K. authorities will be in meters
from the origin, rather than degrees around the center.
Combinational Processing
Combinational processing is generally in-place processing that is the result of various input
operations. It's not too different from using a join in a regular database operation. The result
is a combination of processes and input data steps that ultimately work in real time to
produce a defined input data set.
Pre-Output
Last but not least is the pre-output step. As the name suggests, this is the final processing
required before the output is useable. A pre-output process may include transforming an
internal coordinate system to a more global one; for example, U.K. meters back to a global
scale, or converting a batch of statistics to a different range of values. Location-aware inputs
are often included in this step, typically in a navigation system. For example, a location's
graphical representation could be combined with current mapping to produce a visual output
for a tracking map.
The Database
So just what makes a GIS database so different from a normal database? Honestly, not
much. A GIS database is simply specialized for a particular task.
A better way to illustrate what makes a GIS database unique is to look at the growing world
of big data. These days, it's hard not to notice how much noise is being made by NoSQL and
document-centric database providers. These new-breed databases fundamentally do the
