GeoMedia GIS Blog

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Proportional Circle Maps in GeoMedia

Posted by jeffhobbs on March 26, 2008

Had a very interesting question today on the Directions Magazine GeoMedia list.

Hi fellow ‘GeoMediars‘.
One of my colleagues has asked me about the possibility of doing proportional circles maps in GeoMedia.
Since I don’t know if/how it’s possible, I come once more seeking your help, asking if anyone has ever done this kind of maps?
Best regards
Jorge

There were a few replies. However I did want to highlight one from Phil Hardy as I thought his attached diagrams were very good. He did make sure to let me know that he didn’t create the images himself…so he can’t take all the credit 🙂

1) OK, by Proportional Circle map I assume you mean something like this.

1

2) First, use Functional Attributes to create centerpoints.

2

3) Then use the legend to change the style of the centerpoints.  In this case I assigned size based on the Population attribute.

3

4) And the end result:

4

Simple, but I thought very well diagrammed. It should also be noted that a nice example of this can be seen on the USSample.gws that comes with every version of GeoMedia and GeoMedia Professional  in the GeoWorkspaces folder.

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4 Responses to “Proportional Circle Maps in GeoMedia”

  1. zelazko said

    It is another way – centerpoint + atribute base symbology – 1 legend entry, no thematic

  2. xav said

    Seems a wrong solution. Proportional circles, as the name suggests, must be directly proportional to the dimension shown. So, circle area of a state having 53,2 % of another one must be exactly 53,2 % of this state (see the example map – first picture). Working with classes in then wrong.
    The solution is to create a field containing the radius of the circle and then to use the buffer option. As surface = pop = Pi*R^2, then Radius = sqrt(pop/Pi). of course then, you probably must use a dividing factor or play with units to get a reasonable circle size.
    This solution is not easy but is correct although displaying a legend is difficult…
    I think a software like Geomedia should implement such a basic cartographic functionality.

  3. danielle miller said

    how do you draw a circle map to arang things?i do not want a picture of a united states!!!!!!

  4. danielle miller said

    when you get this please email my back because this is my homework.

    ASAP pleaes:(

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