Placement of Text
Figure 9.14Problem labels in Figure 9.13 are redrawn with the spline text tool.Placement of Text
A visual hierarchy example. The two black circles are on top (closest to the map reader), followed by the gray polygon and the grid.Visual HierarchyVisual hierarchy is the process of developing a visual plan to introduce the 3-D effect or depth to maps.
Another example: The interposition effect in map design.Visual Hierarchy
A map looks confusing if it uses too many boxes to highlight individual elements (and thus has no visual hierarchy.) Visual HierarchyA bad example:No visual hierarchy
Map design – check list1. Choose a map type2. Know your audience3. SymbologyColorSymbolLabel4. Map elementsMain mapTitleBorderNeat lineScaleNorth arrowCreditLegendLabel5. Map designLayoutVisual hierarchy
Data ClassificationData classification is the process of sorting or arranging quantitative data into groups based on their attribute values. Grouping entities into categories based on attribute similarities.Representing members of a group by the same color or symbol. Graduated symbol maps and choropleth maps need to use data classification techniques to map data (interval/ratio)
Classification TechniquesEqual IntervalGrouping observations by using class intervals of an equal range (1-25, 26-50, 51-75, 76-100)QuantileEach class contains the same numberof features. May not be suitable for population counts because some areas have larger populationsStandard DeviationsClass breaks above and below the mean at intervals of standard deviations. Make sure data are normally distributed.Natural Breaks(A.K.A) Jenks method: it minimizes the squared deviations to the class means.
Equal Interval 17.59Data Range 0.0 to 87.98Note: equal ranges, no logical grouping
Equal range: 3%Equal Interval
Same number of objects in each range.Quantile Classification
Quantile Classification46 counties –about 9 counties per group
5 classesEqual IntervalQuantile
Equal IntervalWhat a dramatic difference!Why there seems only one color in the map made with the equal-interval classification?Quantile
Here’s a different color!
Standard Deviation Classification
Standard Deviation Mean = 37.4; Standard Deviation = 21.4 Half the SD = 10.7; Middle interval centers around the mean,from 26.7 to 48.1Mean
Natural breaks is a classification method that partitions data into classes using an algorithm, often called Jenks’ optimization. The algorithm seeks to find “natural” groupings of data values based on the smallest possible total error(which is the sum of squared deviations about the class mean).
Natural Breaks (Jenk’s optimization) … looks for natural groupings and gapsNote Gaps
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- Summer '19
- Cartography, choropleth map, thematic map