I think it's wrong to mention ski maps without crediting Pierre Novat (1), perhaps the original creator of this style (2) since 1962. But what is more important is that Novat actually took the work of Heinrich Berann (3) for Val d'Isère (4) and amended it that result is what we know as ski maps today.

There is some debate about who was first, Berann or Novat, but either way, this was 40 years before James Niehues from the article even started working in this style.

1. https://fr.wikipedia.org/wiki/Pierre_Novat (FR)

2. http://tropfragile.free.fr/galerie/Photos.html

3. https://www.berann.com/panorama/

4. https://www.researchgate.net/figure/Left-of-the-dashed-line-...