Can I symbolize points in map units?
I want to show point features with a specific size expressed in map unit (i.e. 660 ft) but I do not want to create a buffer layer to achieve the same effect. Is it possible symbolize points in map units?
Mapping Center Answer:
You can do this in ArcGIS 10 using an expression and a size field in your attribute table. To do this, you will use a formula that will convert your size in ground units (based on the map scale) to points (72 points to an one inch) which are the units used for symbols.
Here are two examples from which you can see the form of the general equation.
1. 1:24000 scale map; feature width in feet:
size in points = 1/24000 * width (ft.) * 12 in./ft. * 72 pt./in.
2. 1:50000 scale map; feature width in meters:
size in points = 1/50000 * width (m.) * 100 cm./m. * 1/2.54 in./cm. * 72 pt./in.
You can see that the general equation would be:
size in points = RF * ground width * ground width conversion to inches * 72 pt./in.
In your attribute table, you need to have the size attribute in ground units (e.g., feet as in your question). Then on the Symbology tab of the Layer Properties dialog, using the Features - Single Symbol renderer, click the Advanced drop down and select Size... Then click the drop down next to "Size Points by Value in this" and click the expression option. Click the Expression Builder icon to the right and in the Expression area, type in the expression. Click OK to all windows and your features will now be shown in ground units.
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