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Tapered Polygons

September 27 2010 | 2 comments
Categories: Cartographic Representations

I am creating a historic map and want to use tapered streams. I have my streams dissolved by stream order for display (as well as by name for labeling). I can create the tapered polygons but reach a bottle neck at the length. I would like each stream segment to start and end with specific widths however long they are. (i.e., all segment classified as 3 would start at 3mm wide and end 4mm wide, the next segment classed as 4 would start at 4mm wide and end 5mm wide). Is it possible to do this, if so, how?

Mapping Center Answer:

First, you will need to add your streams to a geodatabase. Next, add the streams feature class to an ArcMap session. Then, symbolize your streams using unique values with the Value Field being the stream order attribute.

Add all values and pick a color ramp, then click OK.

Right click the layer in the Table of Contents and select Convert Symbology to Representation. After the representation is created, right click the layer and click Properties. On the Symbology tab, you will see all the Representation rules that have been set up (one rule for each stream order).

Select a stream order rule and click on the + sign, which will open the Geometric Effects dialog box. Choose Tapered Polygon and click OK. A tapered polygon dialog box appears.  In these boxes, enter your starting width (From width) and your ending width (To width), and leave the Length box 0 points. Click OK, and you will see that a polygon outline is drawn, following the shape of the stream line, and the width of the polygon tapers based on the From and To widths. By leaving the Length at 0 points, you are specifying that the representation be draw a polygon along the whole line.

So, you are able to apply specific stream widths at the beginning and end of each line segment, and by leaving the Length at 0 points, you are applying the tapered shape to the entire line segment. Every stream order class will have its own rule, so the From and To widths are applied to every stream segment in a particular class.

Tapered Polygons direction posted by liu aili on Sep 15 2011 11:37PM
I want to make a river map with tapered streams. Accord to your answer? I can control the start and the end. However, if there are body polygons of the river which are linked with the branch line then how can I control the direction of the tapered polygons? Thanks!

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