i made one more visualization that compares observation density from one time period to observation density from another time period, just to see what it would look like. not sure how useful it is, but i thought i’d share since it’s coded at this point.
as an example, this (https://jumear.github.io/stirfry/iNat_UTFgrid_based_density_comparison_map.html?d1=2019-05-18&d2=2020-05-17&d1b=2018-05-18&d2b=2019-05-17) compares all observations from the trailing year to the previous year. the map is explorable (you can pan and zoom), but here’s a static screenshot of the above example at a worldwide view zoom level:
(red means a lot more observations, blue means a lot fewer observations, and green means no or less significant change.)
code is here: https://github.com/jumear/stirfry/blob/gh-pages/iNat_UTFgrid_based_density_comparison_map.html
UPDATE: originally, i included only a relative comparison (A/B), but now i’ve added an optional layer for absolute comparison (A-B).