Bloom Clock/Global Key

The Bloom Clock's Global Keys are an attempt to combine data from the various locations from which contributors have provided data. The original global key is based on the Southeastern Pennsylvania data, which is the largest and most complete set available at this time (with 420 plants over a 17 month period as of February, 2008... see Category:BCP/Flora of Pennsylvania). This region also has the advantage of being on the boundary of northern and southern flora in the US, and the winters there tend to closely follow the calendar winter (solstice to equinox).

Over the next year, the goal is to tie other regions to this standard by checking monthly data from one region against monthly data from Southeast Pennsylvania. This can be done in a number of ways, but perhaps most easily by using DPL.

Matching data from one region to another
As part of the process, each region key has a set of "global comparison worksheets" which use a template to generate DPL lists. To be considered a conclusive match to a season, the data set from a region must be at least 20% the size of the season's data set, and of the keyed data, it must be at least an 80% match (e.g., if there are 8 plants matching and 2 or less not matching, the minimum match is met.

Matches can be checked once per year to refine the results.

Known problems
It should be pointed out from the start that there are issues with this system, including the following:
 * 1) The system will be somewhat inaccurate for regions differing by less than a month
 * 2) The system will be inaccurate in one way or another depending on the ratio of heat-triggered flowers and day-length triggered flowers
 * 3) The system works best when large data sets are compared (thus London is a very poor example)