Tuesday, July 26, 2005

Overview Maps

I have seen several Overview Maps created by users lately and all of them have some common problems. I hope this blog entry will help provide information for building better more useful Overview Maps.

The Overview Map is the overall view of the data seen in the Overview Window. GTViewer, Pocket GTViewer, and GTVx all support an Overview Map. See previous blog entry for more info on the Overview functionality.

Here are some key facts about the Overview Window:

  • The Overview Category defines what is in the Overview Window. The Overview Category type is set to 1 in the .GTM file.
  • All contents of the Overview category are shown in the Overview Window. Display Filters will affect the display in the active view, but not in the Overview Window. If you are turning items off with the filter ids in the Overview Category, you probably have these features in the wrong category.
  • The Overview should be simple and have as few elements as possible while still providing “macro” reference information. This goal is sometimes hard to meet depending on the setup of your original data; however, some effort spent here will make your data look better and make the Overview more useful.
  • The Overview Window always uses a Red rectangle to show where the current view is. So, if your Overview Category contains a lot of red, it is hard to find the indicator. Thick styles can also make it difficult to find the indicator. One solution here is to use the [Overview] style definition to make the Overview Window use weight 0, style 0, and gray colors for all elements:


  • The data range used by the Overview Window is the range provided by the Range or RangeFile entry in the .GTM file. The range defined here should closely bound the data (at least what is in the Overview category) so that there isn’t too much empty space around the data in the Overview window.

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