Dot Mapping

Cartographic Skills - Mod 10

Mod 10 was on Dot Mapping.  Dot mapping is basically a very simplistic form of thematic map.  It uses a dot to represent a certain amount the of phenomenon being mapped.  A dot representing a certain value is placed in the relative geographic location where the phenomenon is most likely to occur.

Dot maps are a very easy concept to understand, but it can be a little complicated getting the computer to place the dots correctly.  I struggled with this for a while before I remembered this problem had come up in the discussion boards.  When I went back and checked, the answer I was looking for was right there.  Once I implemented that correction everything fell into place.  My problem was that the layer I was basing the placements of the dots on, my control layer, needed to be above the layer I was placing them on.  Once I shifted that control layer to the top everything worked right.

Another difficulty with this map is getting the dots large enough to show up, but not so large that in the more densely populated areas they all end up merged into one large blob.  One of our requirements was to make sure there was at least one dot in every county.  In order to do that I had to set my value to represent the size of the least populated county.  With that being 10,000, I had to keep the size of my symbol rather small so in the more populated areas like Miami I didn't end up with a blob.  That made the dots so small they're a little difficult to see in some areas.

But otherwise it was a pretty simple assignment that was pretty quick to complete.