Check on correct earth radius to use in distance calculations

[geanders]

Currently, our default is 6378.14, but it looks like we get answers that are more in-line with online calculators (e.g., https://www.nhc.noaa.gov/gccalc.shtml) if we use 6,371 km, which it sounds like may be the median radius (whereas the other is closer to the maximum radius).

Should we change the default earth radius to 6,371 km throughout? (Likely this will only be ~1 km difference in distance estimates).