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

Multivariate Symbolization

Multivariate isoline maps can be created by display of multiple isoline coverages, with each coverage drawn with a different current line setting. These difference should reflect either the differences in the coverages (nominal differences by differences in hue or shape, for example), or differences in importance (the main data can be drawn last and in a large, black line--with less important data drawn in smaller lines or grays, for example). For fishnets, multivariate maps can be created by use of hue and intensity, or by RGB encoding.

Ratio Data, Nominal Data and Ordinal Data--Surface with Hue and Intensity

Figure 9.2b: SFHI.aml Hue and intensity shaded fishnet surface. This AML can use either a polygon coverage, or two grids; this image is a polygon based (compare Figure 5.5a).

Figure 9.2c: SFHI.aml Hue and intensity shaded fishnet surface. This is the same AML as figure 9.2b, but this figure is based on two grids (compare 7.1c).

Surfaces can be shaded with hue and intensity to show nominal distinctions with meta-data, or another ordinal data set. This AML can display hue and intensity from a polygon coverage, or from two grid layers. See SFHI.aml and Figures 9.2b and c.

SFHI <surface> <hue_lookup> <intensity_lookup> {zfactor} {lattice|tin} {resolution} {nominal_vat_item} {ordinal_vat_item}

<surface>

a grid layer or TIN

<hue_lookup>

specifies HLS hue (from 0 to 300)

<intensity_lookup>

specifies HLS saturation (from 20 to 100)

{zfactor}

`Z' expansion factor--defaults to z-range / the larger of x-range and y-range

{lattice|tin}

the type of <surface>--defaults to lattice

{resolution}

the density of fishnet lines--defaults to the smaller of x-range and y-range / 25

{nominal_vat_item}

specifies an item in the hue grid attribute table other than VALUE

{ordinal_vat_item}

specifies an item in the intensity grid attribute table other than VALUE.

Four Ratio Data Sets--Surface Shaded with Red, Green and Blue

Figure 9.2d: SFRGB.aml A red, green and blue shaded fishnet. This AMl only works with grids; polygon data must be converted prior to display with this AML.

Unlike the other surface draping AMLs, SFRGB.aml only drapes grid layers, which are linearly stretched. If polygons need to be shown with this method, use the polygon to grid conversion AML discussed on page 84. See SFRGB.aml and Figure 9.2d.

SFRGB <surface> <red_grid> <green_grid> <blue_grid> {zfactor} {lattice|tin} {mesh_resolution}

<surface>

a grid layer or TIN

<red_grid> <green_grid> <blue_grid>

three numeric grid layers

{zfactor}

`Z' expansion factor--defaults to z-range / the larger of x-range and y-range

{lattice|tin}

the type of <surface>--defaults to lattice

{mesh_resolution}

the density of fishnet lines--defaults to the smaller of x-range and y-range divided by 25 (half of the default resolution)