• Introduction
• The Utility of Maps
• Producing Displays
• Point Symbolization
• Line Symbolization
• Choropleth Symbolization
  • Monovariate
  • Bivariate Monochrome
  • Bivariate Color
  • Multivariate
• Graduated Symbol
• Grid Symbolization
• Dot Density Symbolization
• Isopleth Symbolization
• Thematic Mapping
• References
• Index
• Author Index
• Symbol Index
• Site Map

Monovariate Symbolization

Monovariate symbolization techniques for area data involve the use of hue, value, orientation and shape to represent data. This can be done when only one variable needs to be shown, or as an inset for bi- or multivariate maps.

Nominal Data--Hue

Hue is best for representations of nominal data. In ARC/INFO's default shadeset, there are only three colors (red, green and blue) available--shade patterns 2, 3 and 4, and white--shade pattern 1. Rather than using the limited default colors, SHADECOLOR can be used to specify the output color. SHADECOLOR requires that the shadetype be set to a type other than the default HARDWARE, such as COLOR. When this is done, hues can be specified directly; an alternate method is to use one of ARC/INFO's color shadesets: COLOR.SHD and COLORNAMES.SHD. This AML (CH.aml) accomplishes the display of a data set with the shadeset method; see Figure 5.1a.

CH <cover> <data_item> <lookup_table> <shadeset>

<cover>

a polygon coverage

<data_item>

the item in Polygon Attribute Table of <cover> referred to in <lookup_table>

<lookup_table>

relates data item to shades in <shadeset>

<shadeset>

a shadeset file.

Monovariate Legends--Filled Polygons

In keeping with the idea of presenting as much information as possible in legends, AL.aml generates monovariate legends for area data that include the number of polygons in each category as well as defining the category symbolization. The AML automatically labels each category, as well as adjusting the display for nominal (discreet symbols) and ordinal (or better) data (continuous symbols). See Figure 5.1b for nominal data, and Figure 5.2b for ratio data.

AL <lookup_table> <start_x> <start_y> <size_x> <size_y> <h|v|t|a|l> {color_parameter_1}
{color_parameter_2} {line_size} {textset} {font} {point_size} {floating_point_precision}

<lookup_table>

the lookup table that a legend will be based on

<start_x> <start_y>

the lower left corner of the legend area

<size_x> <size_y>

the size of the legend--all locations are in PAGEUNITS

<h|v|t|a|l>

the symbolization method: Hue, Value, Texture, orientation (Angle), or
shadeset symboLs

{color_parameter_1} {color_paramter_2}

Hue: value and saturation (default: 50 and 100)
for Value: hue and saturation (default 0 and 0), no effect for other symbolization

{linesize}

for Texture and Angle line width--defaults to 0 (minimum displayable width)

{textset} {font} {point_size}

define the labelling text--defaults to a 10 point roman font

{floating_point_precision}

the number of decimal places to be shown--the default is 2.

Nominal Data--Orientation

Orientation is best used for nominal data. There are three ways of achieving changes in area fill orientation: selecting a subset of a shadeset that has a pattern that changes in orientation, the POLYGONSHADES command (see Ordinal to Ratio Data--Orientation), and the SHADEANGLE command. The AML, CH.aml, uses the PLOTTER.SHD shadeset's symbols; see the above discussion of the AML and Figure 5.1c.

Nominal Data--Shape

Shape is best used for nominal data. The SHADETYPE command allows the specification of a marker to be used for the area fill. The macro, CS.aml, makes use of the Agfa Compugraphic font set to change area fill shape; see Figure 5.1d. Note the use of a loop to set up area fills.

CS <lookup_table> <shade_size> <shade_separation>

<lookup_table>

contains Agfa Compugraphic glyph numbers (font 94021)

<shade_size>

a size for the glyph symbols in PAGEUNITS

<shade_separation>

the separation of the glyphs in X and Y in PAGEUNITS.

Ordinal Data--Value

Color value is best used for ordinal data. A new command in ARC/INFO release 6.0 allows the rapid generation of ordinal maps based on color value. The command SHADECOLOR allows a 'true color' specification of area fills. Prior to using SHADECOLOR, the shadetype must be set to color. Once this is done, colors can be specified by one of several color models (such as HLS, RGB and CMY). This macro uses lookup table symbols to specify value (lightness) in the HLS color model; see Figure 5.2a and CV.aml.

CV <lookup_table> {hue} {intensity}

<lookup_table>

specifies HLS lightness (values from 0 to 100)

{hue} {intensity}

specify a color that will be value shaded.

Ordinal to Ratio Data--Orientation

For interval/ratio data that should not be classed and is continuous with abrupt spatial changes (that is, it should be displayed as a choropleth map), ARC/INFO provides one automated way of generating an unclassed choropleth map. It uses changes in the orientation of area fills to vary the symbolization. The POLYGONSHADES command is used with an area fill pattern that will show angular changes (not a solid color fill, for example), such as shade 5 of PLOTTER.SHD, and an angle item (preset to a range from 0 to 180 degrees) in the Polygon Attribute Table. This AML displays this kind of data; see Figure 5.2c and CAO.aml.

CAO <cover> <angle_item> {shadeset} {shadesymbol}

<cover>

the polygon coverage to be displayed

<angle_item>

a numeric data item in the Polygon Attribute Table of <cover>

<shadeset> <shadesymbol>

select a shade to be oriented--defaults to plotter.shd 5.

Monovariate Legends--Orientation

Because orientation can be used in point symbols as well as area symbols, the AML that follows is designed to work with either coverage type. It is also allows specification of a data variable that is not the same as the item that determined the drawing angle--an attribute item can be rescaled in INFO, for example, into another item and the second item can be used to draw area fills. The original item still holds the data values that the angles represent. By assuming a linear transformation between data values and angles, this AML can label the angles with an interpolated data value. See Figure 5.2d and OL.aml.

OL <cover> <point|poly> <data_item> <angle_item> <start_x> <start_y> <size> {textset} {font} {point_size} {float_precision}

<cover>

the point or polygon coverage with angle data

<point|poly>

the coverage type

<data_item>

the original data field

<angle_item>

the data field used to display rotated symbols

<start_x> <start_y>

the location of the center point of the legend

<size>

the length of each radiating line, in PAGEUNITS

{textset} {font} {point_size}

define the label test--defaults to a 10 point roman font

{float_precision}

the number of decimal places to be shown--the default is 2.