Geography Reference
In-Depth Information
In-Depth
Suggested Map Elements
Cartographers would likely argue for days and nights about which elements are
necessary in a “good” map. For pragmatic purposes, there are six elements
that people agree are helpful, even if not always necessary:
•
Scale indicators show the relationship between distance measures on
the map and the actual ground distance. Scale bars are most common
and practical. The representative fraction provides important informa-
tion for experienced map users.
•
Legend explains what the symbols used for a map mean.
•
Title provides a simple description of the map, possibly also indicat-
ing potential uses and audience of the map.
•
Author offers readers the name of the institution, group, or individ-
ual responsible for creating the map. It can help point to the accep-
tance of the map.
•
Orientation (North Arrow) helps people orientate themselves when
using the map.
•
Date indicates when the map was produced and may also suggest
when the data was collected.
Explanations and contact information can additionally be included, if
they are important for communication, or necessary to ensure that readers can
find relevant information for more specific questions.
Note that these six map elements do not necessarily refer to visualizations.
Although they can be considered for a visualization, the constraints on a visu-
alizations of size and length of display mean that map elements should only be
used when absolutely essential to communication.
Scale
The geographic area shown on a map must be at a scale. The selection of
scale and the use of scale have many consequences. The most important
thing to remember is that large areas are shown with GI or in maps and visu-
alizations at a small scale, which small areas are shown at a large scale. This
may be at first glance counterintuitive; however, scale always states the rela-
tion between one unit of distance on the map and the same unit of distance
on the ground. “Large scale” refers to a large ratio between map and ground
units; “small scale” refers to a small ratio.
Scale for maps and GI, in other words, is usually expressed as a mathe-
matical relationship. However, this is only one of three ways to express scale.
Scale can also be expressed in words—for example, “1 inch equals 1 mile” or
by using a scale bar.
The representative fraction is the most important way to represent
scale. It offers a clear indicator of the relationship between distance mea-
surements on the map and distances on the ground and vice versa. For
instance, many topographic maps from around the world are published at a
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