Thanks. I was mostly basing my answer on my experience with nautical charts, where declination corrections are typically uniform over relatively large areas and local anomalies are less of a concern. I hadn’t considered how much more variable the field can be in terrestrial use.
From that, you can pre-compute a low-resolution declination grid. NOAA even provides one here:
https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#i.... That’s only a few KB of data and requires just a simple declination subtraction based on lat/lon, similar to how it’s handled on nautical charts. This works fine as long as you stay away from the poles (and Alaska).
Quality of air in established modern cities has been vastly improving in the last decades [1] and is subjected to much scrutiny nowadays. I doubt many cities ever had a comparable effect to smoking 10 cigarettes a day.
There's one advantage to this way of scrolling most comments seem to miss:
When you go to the next page by hitting Space or Page Down there's an interruption in the flow and you have to refocus at the top of the page once you're finished with the current page.
Here I like the fact than I can already start focusing at the top of the page while finishing to read the page at the bottom.
Weird, yes, but it has at least this advantage over classic pagination display.
Not anymore. That is exactly the purpose of Darpa Ambient program: https://www.darpa.mil/research/programs/atomic-magnetometer-...
Demo from 2022: https://www.youtube.com/watch?v=VTnIXWCBYTw