Four Major Types Of Thematic Mapsdot

Front 1

Dot Map

Back 1

representation of geographic phenomena on which dots represent a specified
number of the phenomena being mapped. It can show the details of the locational character of
a spatial distribution more clearly than any other kind of map.

Hint 1

Purpose – to communicate the spatial variability of density of discrete geo data.

How accomplished – by providing an easily understood visual impression of the
relative density of a spatial distribution.

Nature of data – discrete, point data, nominally scaled, enumerated by area.

How symbolized – uniformly sized dots, placed randomly w/in enumeration area,
with a stated dot value.

Major considerations – dot value, dot size, and dot placement (avoid white channels).

When used – spatial distribution is concentrated in some areas and sparse elsewhere.

Front 2

Graduated Circles Map

Back 2

type of quantitative thematic map in which point data are
represented by a circle whose size varies with the data values.

Hint 2

Purpose – to communicate the spatial variability of density of discrete geo data.

How accomplished – by providing a graphic representation of the spatial variability of
the geo data in such a way that the map reader can form a picture of the quantitative
distribution by examining the pattern of differently sized circles.

Nature of data – discrete, point data which occur at points or are aggregated at points.

How symbolized – ordinally or intervally scaled circle symbols drawn proportional to
the quantity represented and centered on a point (e.g. county centroid).

Major considerations – method of scaling of circles, variability of the distribution,
reader estimation of circle area comparability, standard or index circle, overlapping
circles (draw smaller circles first).

When used – when data variation is moderate and not localized

Front 3

Isarithmic Map

Back 3

a planimetric graphic representation of a three dimensional volume.

Hint 3

Purpose – to portray the undulating surface of a 3D volume.

How accomplished – by use of a system of quantitative line symbols defining the form
of the model’s surface.

Nature of data – continuous, smooth, volumetric, symbolized by an interval/ratio line.

How symbolized – isolines intervally scaled amd labelled periodicalluy.

Major considerations – number of data points, location of data points,
interpolation,domination on map of isolines.

When used – data is in form of geo volume and continuous in nature.

Front 4

Choropleth Map

Back 4

a form of statistical mapping used to portray discrete data by enumeration
units.

Hint 4

Purpose – to obtain a sense of the overall geo pattern of the mapped variable with
attention to individual values. To compare one map’s pattern with another’s.

How accomplished – by combining mapped values into classes, symbolizing each class
with a unique areal symbol.

Nature of data – discrete, ratio scaled, data which occur, or can be attributed to, definite enumeration units. Rates, ratios, proportions, percentages.

How symbolized – by applying appropriate areal symbol to the enumeration units
depending on each unit’s data value.

Major considerations – geo phenomenon being mapped, map scale, # and kind of
enumeration units, data classification method (e.g. equal steps, quantiles, natural
breaks, Jenks optimization), areal symbolization and legend design.

When used – portraying a geo theme whose data are discrete and occur within well-
defined enumeration units.

Front 5

Topographic Maps

Back 5

Contour Interpretation

Hint 5

Contours – Lines of equal elevation; index, intermediate, depression; define terrain
features (e.g. hilltop, saddle, draw, spur, ridgeline, valley); V-ing of streams

Contour Interval (CI) – the higher the CI the more rugged or mountainous the terrain

Contour Spacing – reflects variations in slope

Slope – rise over run; steep, gentle, uniform, convex, concave; expressed as a gradient,
percent, or degree.

Profile – a cross-sectional view through a particular piece of terrain; cut-line; vertical
exaggeration