Map symbols should be designed or chosen according to
principles of logic and communication to serve as a graphic code for
storing and retrieving data in a two or three dimensional geographic
framework.
Appreciating
the logic of map symbols begins with understanding the existence of
three distinct categories, including
point, line and
polygons (areas).
Maps and
models include generally a combination of all three. These tree
main categories can be further differentiated by variations in "hue"
(color), "gray tone value", "texture"
and "orientation", "shape"
and "size".
Each of these
variables or their combinations excel in portraying particular features and their variations.
When using
color (hue)
for characterizing areas, decoding is made simpler when darker means
"more" and lighter means "less". Color conventions allow map symbols to
exploit idealized associations of water with blue and forested areas
with green. This the combination of the two, implies that dense primary
forest is dark green, secondary forest green, and grassland light green, and that
deep waters are dark blue and shallow waters light blue .
"Size" is more suited to for showing different in amount of count,
whereas "variations in gray tone" are preferred for distinguishing
differences in rate or intensity. Symbols varying in orientation are
useful mostly for representing directional occurrences like winds,
migration streams or other. Line symbols best portray water courses,
roads, trails, boundaries and may combine different variables, including
color and size (thickness). A heavier line readily suggests greater
capacity or heavier traffic than a thin line implies.
Each symbol should be easily discernable from all others
to clearly distinguish unlike features and provide a sense of graphic
hierarchy. A poor match between the data and the visual variables may
frustrate and confuse the map user.
While in 2-dimensional mapmaking the only limitation in the
choice of symbols is fantasy (with logic), 3-D modeling frequently depends on the
availability of materials, particularly for
point features which are
generally represented by push and map pins.
Lines and
polygons can be
easily represented by color-coded yarns and different color paints.
Standardization of symbols serves for ready unambiguous
recognition of features and promotes efficiency in both map production
and use, exchange of data and comparison. Maps and models sharing a
common graphic vocabulary are definitely more powerful in convening the
intended message and decoding simpler.
