The blog of

Sat Dec 11, 2021 14 Projections for 2021 (Part 12)

If you wonder what this is about at all, you probably didn’t read the intro.

December: F13 Copycat

F13 Copycat
Creator Karlheinz Wagner, Tobias Jung (1941 / 2020)
Group Lenticular
Property Compromise
Other Names
  • Wagner vii@60-77-60-45-170
Remarks Wagner VII variant, configuration 60-77-60-45-170 (using the Böhm notation, see Umbeziffern – The Wagner Transformation Method.

Experimental, a Frančula XIII copycat, with bit less areal inflation.

Briefly introduced in my blog.

This month, the selected projection is the F13 Copycat, one of my own experiments. I introduced it a year ago in the blogpost about the Frančula projections (see link above) – and that’s how it got its name, because it’s a copycat of the Frančula XIII.

Everything else is basically mentioned in the blogpost, so there’s no need that I get chatty here … no, wait, there is a thing: I mentioned that the F13 Copycat has good distortion values according to Capek’s Q[1] but meanwhile, thanks to Peter Denner, I know that is also is quite decent according to the metric of Goldberg & Gott[2] and the Airy-Kavrayskiy criterion.

Here are images showing isolines of angular deformations and areal distortions, once again provided by Peter Denner. 🙏
The isolines are given for max. angular deformation of:
  10°,     20°,     30°,     40°,     50°,     and 60°.
For the areal inflation, shown normalized to the value at the central point of the map, the lines represent values of:
  1.5;     2.0;     2.5;     3.0;     and 3.5.

But – this isn’t the projection I actually showed on the December sheet of the calendar! There, I used another one of my own experiments, namely Wagner BCW-A I:

Last I year, I chose this projection because – well, firstly because I always like to smuggle in one or two of my own projections. 😉 Secondly, because the BCW-A I has a very decent Q value: 82.4, which would be rank #5 in Capek’s list of 100 projections. But it turned out that the distortion values according to Goldberg & Gott and the Airy-Kavrayskiy criterion aren’t that great. And so, I chose to cheat a bit and pretend I presented a better one …

So. We are through with that.
We have ploughed through the entire 2021 calendar. I hope you had a bit of fun. If so, you will be might to learn that there will be a 2022 calendar! Once again I decided to use a leitmotif for the calendar. I will reveal what it is in January.

See you!


  1. Richard Capek, 2001:
    Which is the Best Projection for the World Map?
  2. Goldberg & Gott, 2007:
    Flexion and Skewness in Map Projections of the Earth

My 2021 Map Projection Calendar

To read another part of my 2021 map projection calendar series, select the desired month.


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