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  • 1.  MapInfo Monday: Which Thematic Map would you use?

    Employee
    Posted 02-07-2022 03:50
    Happy #MapInfoMonday, from my chair it's a wonderful sunny day,

    Today's article is a bit different from the earlier articles. I thought I would try to get you involved a bit more by discussing some options. ​As you probably know, most things in MapInfo Pro can be done in a number of ways. Some ways tend to be a bit better than other ways, however.

    Let's have a look at visualizing the population on a map. How would you do this? Let me give you a couple of ways and hopefully, you will help me pick the better option, or even suggest an alternative.

    Ranged Thematic with Counts

    The first suggestion is the use the standard Ranged Thematic and colorize the polygons based on the number of inhabitants.

    This is easily done. From the Add Theme control, you pick the thematic type, a template and then you select the table and column to use.

    The Thematic Map clearly shows the areas with a higher population in darker colors.

    Ranged Thematic with Density

    The second suggestion is also using a Ranged Thematic but instead of using the population count directly, I will divide it by the area of the polygons to get a population per area unit, in my case square kilometers.

    The process is similar to the above but instead of selecting a column, I use the Expression... option to calculate the value for my thematic map. Below you can see the expression I used. Noticed that I used the CartesianArea calculation as my data are using a projected coordinate system. If you are using Longitude/Latitude data, use Area instead.

    The resulting map is quite different from the previous one as it now takes the size of the polygons into account as well.

    Dot Density

    The third and final option that I wanted to give you today, is the Dot Density Map.

    Dot Density is a different thematic type. It allows you to assign a value to each point rendered in each polygon. In this way, each point will represent a number of inhabitants, as an example. In the example below, you can see that I assigned the value 1,000 to each point.

    You can assign a different color but black to your points too if you prefer a more colorful map.

    The Dot Density Map is somewhat similar to the second option I shared with you. This becomes clearer if you have both layers on a map.

    Now over to you. Which option would you use? And why? Or maybe you have an alternative?

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    Peter Horsbøll Møller
    Principal Presales Consultant | Distinguished Engineer
    Precisely | Trust in Data
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  • 2.  RE: MapInfo Monday: Which Thematic Map would you use?

    Posted 02-08-2022 08:45
    Thematic density is usually good. Dot density has the disadvantage that people read the dots as "truth", and where you've got a city with a surrounding rural area within the same region, the dot pattern is not representative of the real pattern which can get people confused. Probably works better where you've got more granular data with areas that are internally homogeneous.
    For other thematics I often contextualise by putting on a grey dot in a very small point size for each house location as background, which gives a visual but not intrusive picture of urban-rural split- but that only works on a more local geography.

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    Martin Burroughs
    Oldham Council
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