# How to present three spatial variables in one map? [closed]

I want to assign 3 category of variables in a single map. In other words, I have to produce a cartographic visualization of the damage including a legend listing:

• damaged surface area in the residential areas (in km2),
• number of living units and number of people affected, and
• damage in terms of euroes.

I just can present two of them by "graduated colors" and "graduated symbols". I cannot add third variable, in a meaningful way.

How I can present all the 3 variable in a same snapshot simultaneously?

• Is your data points, polygons, or a raster? And you seem to have listed four things - item 2 has a couple of things... – Spacedman Nov 28 '12 at 22:28
• You could try some of the solutions suggested in answers to Effectively displaying demographic data on a printed map question. – radek Nov 28 '12 at 22:33
• Do you have a map layer for the damaged surface areas? I would suggest that the map layer itself would display the damaged area. That leaves the two remaining variables, which you can plot with the colors and symbols. – jvangeld Nov 28 '12 at 23:59
• You can try using charts, pie, column or stacked – nadya Nov 29 '12 at 2:52
• Perhaps a 3D (perspective view) of the area, with a couple of columns or other icons)? It may be a problem depending on the "depth" of the view. – BradHards Dec 7 '12 at 4:54

Assuming polygon layer

1. Damage in euros: polygon outline thickness
2. surface damage in km2 polygon transparency
3. Number of units polygon color ramp or chloropleth symbology

You want to represent four variables:

• damaged surface area in the residential areas [km2]
• number of living units affected
• number of people affected
• damage [euroes]

All these variables are absolute values.

Assuming you have polygon layer please take into account:

Absolute data should not be used in choropleth mapping. Do not use a color ramp to color the area (fill color) of a polygon. So do not do this if you want to show “number of people affected”: Color ramp: bright red to dark red

Instead of showing absolute values you should show relative values: You can divide the “number of people affected” by the “number of people living in this area”. ArcView is able to calculate this on-the-fly (layer properties dialog). Then you can use a color ramp to color the area (fill color) of a polygon.

If you want to show absoute values (“number of people affected”) you have to use dot distribution or proportional symbols.

I see no possibility to use charts. I.e. there is no sense to show the “number of people affected” and the “damage [euros]” together in one pie chart.

I think that it's too much to show all your 4 values in one map. Often it is better to make several maps.

You can use a Synthetic Map (i'm not sure of the terminology so correct me please), here an example this maps using 3 variables, or you can plot your data to identify the tending groups like in this example , so you may reduce the complexity of your variables to a limited set of clusters.

source web page http://people.oregonstate.edu/~whitede/ternary.htm