I do a lot of work with maps of the F2 layer of the ionosphere. I found two good articles, (so far), this week that I wanted to pass along. The first has to do with the ionosphere itself and how signals propagate through it. The Department of Commerce book , ( here's the older 1948 version ), on the ionosphere that I frequently quote and more frequently use cites a number of formula and diagrams without a whole lot of explanation. I finally checked out the references this week and found that much of the information I use from that book—including the figure below—comes from this more information-dense paper by Newbern Smith. The second paper hits on the topic of quaternions—one of my perrenial favorites—in relation to rotations in video games. How did I find it? Using ChatGPT to prototype mapping apps again, of course. I wanted to find what squares on a spherical map of the Earth a QSO path traveled through. ChatGPT suggested susing something called a slerp . Wondering if t...