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Any tips for visualizing both points and polygons that are essentially from the same dataset?

July 16 2007 | 0 comments
Categories: Symbology

I am mapping geopolitical data organized into polls. Most of the polls are represented by
polygons but some polls are so small that they are stored as points. It is confusing to the novice map reader to have polls represented as polygons AND points. Any tips for visualizing both points and polygons that are essentially from the same dataset?

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I am showing thematic information about the polls. The thematic information I am showing is election results. I am assigning a specific color to each poll based on the election result.

In some cases the point polls are concentrated and in other cases they are spread out

Just to be safe, a poll is a geographic area used to determine where someone votes on election day. Everyone who lives in the same poll votes at the same voting location. Election results are readily available on a poll-by-poll basis, hence the need to do some poll mapping.

Mapping Center Answer:

Do you just want to show the locations of the polls or are you also needing to show thematic information about them. Also are the small polls concentrated in any given area or are they spread fairly evenly across your area of interest? Also, just to be safe, could you describe what a poll represents?

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So this would be my opinion on how to approach this. In the U.S. we would call these kinds of information voting precincts (areas or points) and polling places (the physical location where people go to vote). So, one route you could take is to get the locations of all the polling places and geocode them so you’re showing only points for the results (making for a consistent result geometry type). You could then just draw boundaries for the large precincts (as background context on the map), and label them as well (to help show a correspondence between the precinct area and its polling place).

If, by looking at the map I thought it was important enough, I would go one step further and denote the point-based precincts with special symbol. One way would be to draw a line underneath those symbols—the convention I’m thinking of is some maps underline capitol cities to help distinguish them from the surrounding cities. You could also reinforce the whole thing by including a graphic table beside the map body that lists the polls and the results, potentially saving the reader from having to spend extra time looking at the map, trying to find a specific poll when they could just read the information in the table.

All that said, I don’t know what story the data is telling or that you’re trying to tell and the map design should be tailored to that first and foremost.

Hope that helps,

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