This map compares iNaturalist observation density between 2 time periods.
The current time period is defined by the paramters d1 (beginning observation date) and d2 (ending observation date), and the time period for comparison is defined by parameters d1b and d2b. You must input valid dates for all 4 of these parameters for this page to function properly. For example, this compares observations in 2019 to observations in 2018: .
This will also handle other filter parameters added to the URL. For example, to see just bird observations, add "&taxon_id=3" to the end of the URL.
By default, the comparison is relative (A/B), and it is visualized on a log base 10 scale, where a value of 1 (1000% current vs comparison period) or more is red, a value of 0.5 (~316%) is yellow, a value of 0 (100%, or no change) is green, a value of -0.5 (~32%) is cyan, and a value of -1 (10%) or less is blue. In locations where there are no observations in the current time period, there will be a blue ring (unfilled circle). In cases where the comparison time period has no observations, there will be a red ring in that location.
There is also an optional absolute comparison (A-B), and it can be selected in the layer selector (in the top-right corner of the map). If you prefer absolute comparison by default instead of relative, use defaultstyle=absolute in your URL parameter string. Increases (A-B>0) are visualized on a log base 10 scale where a value of 0 (+1) is green, 1 (+10) is yellow-green, 2 (+100) is orange, 3 (+1000) is red, and 4 (+10000) or more is magenta. Decreases (A-B<0) have a gray ring and are fill-colored on an opposite log base 10 scale where 0 (-1) is green, 1 (-10) is blue-green, 2 (-100) is light blue, 3 (-1000) is dark blue, and 4 (-10000) or more is magenta. Zero change is denoted by a gray ring with no fill.
Default map center is 0,0 and default zoom is 2. You can change this by setting centerlat, centerlng, and defaultzoom parameters appropriately. Finally, you can hide the left pane by using hideleftpane=true.
For more information and other examples of UTFgrid-based density maps, see