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Point Symbol Mapping

Proportional Symbols

True vs conceptual point data

geometric

pictographic

Scaling of symbols: Interval and ratio (sometimes ordinal = range grading)

mathematical (formulae, problems)

perceptual

Legend (nested or linear): Bar

Linear: problems with figure ground contrast

Symbolization

Transparent vs. Opaque

Overlap vs scaling and zoom

redundant symbols

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Dot Mapping

Problem of unevenness of uniform area assumption

Leads to Dot and Dasymetric maps

Dasymetric maps (part isopleth, part choropleth)

Jumps allowed.

Dependent upon ancillary variables (J. K. Wright, 1936 map of Cape
Cod)

Dot maps are suitable for raw counts

Manual vs. Automated

Deciding on dot size and unit value

Nomograph (Robinson)

Dot density shading (even vs random, base on grids)

Langford & Unwin: Population Density (1994) = filtered dasymetric
map