To represent locations measured in a projection sys-
tem to locations on a map or coordinates used for
geographic information, the locations are scaled.
Scale also constrains how things, events, and geo-
graphic relationships can be shown.
Which scale is best suited for showing the river flooding?
What scale best balances detail for the cartographic prod-
Points, lines, areas
Vector data can be easily transformed between these
geometric types, expanding cartographic representa-
The river, geographically represented as a line, could be
converted to an area. Would this help people understand
river flooding better or confuse them into thinking the river
is much wider than it is?
Cells or pixels
Raster data can be shown either as cells, which take
up an area, or as a pixel, which is single dot, much
like the dots making up the image on a TV screen,
which combined show an area.
If the river is geographically represented as raster data,
does the presentation of the river as cells or pixels help the
The symbols for elements from the geographic repre-
sentation can be varied in terms of size, shape, value,
texture, orientation, and hue.
Should flooding be shown by changing the hue from blue
to red as danger increases?
Geographic information and maps are collected and ultimately made to
communicate. How this communication works is important to think about
because this ref lection helps improve the geographic information and maps
that we make. A more detailed consideration of the underlying issues follows
in other chapters. The clearest communication results from the successful
consideration of the many aspects of geographic and cartographic represen-
tation in the context of the purpose and any and all relevant disciplinary or
professional conventions. After all, how the content can be communicated
depends on geographic representation and cartographic representation
choices. If you only count the list of choices made so far in this chapter (14),
this means a total of 195 choices, which is still barely scratching the surface
of the infinite potential in map design.
Before looking at the practical demands of geographic information and
cartographic communication, we should consider an example of the relation-
ship between geographic representation and cartographic representation. A