Electronic maps
A USGS digital raster graphic.
An example of a map generated by the King County GIS service called [I.map
Map Sets]From the last quarter of the 20th century, the indispensable
tool of the cartographer has been the computer. Much of cartography, especially
at the data-gathering survey level, has been subsumed by Geographic Information
Systems (GIS). Even when GIS is not involved, most cartographers now use
a variety of computer graphics programs to generate new maps. Interactive,
computerised maps are commercially available, allowing users to zoom in
or zoom out (respectively meaning to increase or decrease the scale),
sometimes by replacing one map with another of different scale, centred
where possible on the same point. In-car satellite navigation systems
are computerised maps with route-planning and advice facilities which
monitor by satellite the position of the user.
From the computer scientist's standpoint, zooming in entails one or a
combination of:
replacing the map by a more detailed one
enlarging the same map without enlarging the pixels, hence show more detail
enlarging the same map with the pixels enlarged (replaced by rectangles
of pixels); no additional detail is shown, but, depending on the quality
of one's vision, possibly more detail can be seen; if a computer display
does not show adjacent pixels really separate, but overlapping instead
(this does not apply for an LCD, but may apply for a cathode ray tube),
then replacing a pixel by a rectangle of pixels does show more detail.
A variation of this method is that interpolation is performed.
For example:
Typically (2) applies to a Portable Document Format (PDF) file. The increase
in detail is, of course, limited to the information contained in the file:
enlargement of a curve may eventually result in a series of standard geometric
figures such as straight lines or arcs of circles.
(2) may apply to text and (3) to the outline of a map feature such as
a forest or building.
(1) may apply to the text (displaying labels for more features), while
(2) applies to the rest of the image. Text is not necessarily enlarged
when zooming in. Similarly, a road represented by a double line may or
may not become wider when one zooms in.
The map may also have layers which are partly raster graphics and partly
vector graphics. For a single raster graphics image (2) applies until
the pixels in the image file correspond to the pixels of the display,
thereafter (3) applies.
The word "map" has also been used to describe places within
video games, such as SOCOM II: U.S. Navy SEALs and Counter-Strike, that
players choose to compete on, as a synonym for level.
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