Computer Cartography midterm
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Dasymetric mapping
 first referenced in 1936 by J. K. Wright
 show densities of anything

intangible maps
 mental maps
 maps that you carry in your mind
 it can be drawn and converted to a tangible map

qualitative maps
 what is shown at a particular location
 they don’t display the quantity of item that can be found, just what is found
 can display names of areas

cartogram
 symbols are used but the size varies based on quantities
 distortion displays different types of data

enumeration unit rules
 block is considered to be the basic unit for the census, for privacy reasons
 there are larger units above it, like county and state
 3 rules of thumb as to how many categories should be defined on a map breakdown
 7±2 = 79
 2^{x} < n < 2^{x+1}, where 2^{x} = the largest value below the total
 Ex.: if total is 100 then 2^{x} = 2^{6} = 64

Choropleth map
 always use derived/standardized values
 Do NOT use absolute values or actual numbers
 Use derived values that only show rates, densities, or percentages

linear features
 Italic
 Blue
 Label should be on top of the feature, not bellow
 If it’s too long put the name multiple times
 On rivers use regular kerning
 If river is a polygon, apply polygon rules

Map titles
 in ALL CAPS
 Include area covered
 Time frame of the map

Class interval methods
 Equal steps
 Quantiles
 Arithmetic progression
 Geometric progression
 Optimal
 Natural breaks
 Standard deviation

Quantiles
 create classes with the same number of values in each class
 generic name for any number

Optimal
 Prefered method
 put values into a class that are very similar and each class is very different
 internal homogenous
 external heterogeneous
 default method used in ArcGIS
 good choice
 Chenks wrote an article in the 70s and defined the Chenks method

Natural breaks
 Prefered method
 Look for valleys, natural breaks (low points), in the frequency distribution
 Graphic array
 sort values by size and organize from smallest to largest
 apply the breaks where there is a difference

Proportional symbol mapping
 next to choropleth mapping it’s the 2nd most popular type of maps
 can map absolute and standardized values
 a symbol type is selected, usually a circle
 can map both aerial and point information
 centroid of the enumeration unit
 flexibility is higher
 can be collected for polygons or point locations
 different techniques used for proportional symbol mapping

proportional symbol mapping techniques
 absolute scaling (not used much any more)
  sizes of the symbols are mapped proportional to the quantities they represent
  need to know how to calculate the exact symbol type
 Apparent (magnitude) scaling
  lots of comparison between 2 different sizes
  developed based on the study of people’s interpretation of the sizes
  discussed in the article
 Range grading is used today
  Distinguish ability is very important
  usually the smallest circle is on top and larges is at the bottom
  can use numbers easily remembered, not easily remembered and ranges
  do not put more than 23 attributes on a map at the same time

Isarithmic map
 divided into 2 categories: isometric and isoplethic
 made by connecting points of the same value
 usually included in many GIS packages
 3D representation of a surface
 Fishnet option
 can be rotated and angles can be changed
 Shaded relief presentation
 east slopes are typically light, the west are dark

Isometric map
data is collected at points

Isoplethic map
data for areas

triangulation
 use of triangles to identify areas
 isolines need to be smoothed out

interpolation
 if there are different values they can be displayed in several ways
 foreground information should be displayed more prominently
 if the isaline is longer than label it more than once

Cartogram
 uses size and shape distortions
 no symbols
 no fill
 contiguous cartogram: boundaries stay together as in reality just deformed
 noncontiguous cartogram: boundaries are separated

3 twodimensional symbols used for proportional symbol maps

 proportional symbol map shows spatial numerousness
 dots should coalesce in densest parts of the map

 Classed and unclassed choropleth maps
 top is the 4 class conventional
 bottom unclassed


voluminous and bounded by continuous surface


Planimetric map: shows the model's surface

Thematic map with enumeration unit being a county



distributive type of line map