Specifying the Number of Intervals on your Scalebar
A very important factor in how your scalebar looks is the number of intervals drawn. The Ultimate Scalebar has two basic classes of scalebars, and the number of intervals is calculated differently for each.
You can specify the number of intervals on your scale bar by setting the global variable .scalebar$intervals before running the AML. If this variable is not set, then a default value of 5 will be used.
Controlling Which Numbers Appear
In conjunction with the number of intervals, you can control what values will appear as your major scalebar label, the largest number appearing on your scalebar. For example, if you want only to see a multiple of 10 as the major scalebar label, then you can set .scalebar$validintervals to 1 or 10. If you want to allow the program to have more flexibility in choosing a major scalebar interval, which will allow the scalebar to be drawn closer to your specified length, you could set .scalebar$validintervals to a space-delineated list of values, such as 1 2 4 6 8. If you change the default valid interval list to one incompatible with the number of intervals on your scalebar, you may get unaesthetic decimal numbers appearing on the minor intervals.
Generally, the fewer numbers you allow to serve as your major scalebar label, the less flexibility the program will have in rendering your scalebar, so the more your actual bar length may differ from what is specified on the command line.
Ultimately, the choice of intervals and values are a matter of aesthetics. Some good combinations of values for .scalebar$intervals and .scalebar$validintervals that I have found are summarized in the following table:
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