Use GRASS GIS temporal framework

[mankoff]

The initial manuscript assigned each raster to the central time-stamp, even though each raster represents a time-span. The GRASS Temporal Framework [1,2,3] supports time-spans. The algorithm should be modified to take advantage of time-span data storage. Visualizing this is easy, and can be done as in [4] (see also example figure from that paper included below).

Limitations and Issues:

• Converting those boxes to a single numeric value for any given date or annual average is a new challenge.

• Each pixel within the raster may have a different time-span, or be some weighted average of multiple time-stamps within the time-span. That information is not likely to even be exposed at the level where we access the data.

[1] Gebbert & Pebesma, 2017 http://dx.doi.org/10.1080/13658816.2017.1306862
[2] https://grass.osgeo.org/grass70/manuals/temporalintro.html
[3] https://grass.osgeo.org/grass76/manuals/g.gui.timeline.html and
[4] Hanna /et al./, 2013 https://www.nature.com/articles/nature12238

[mankoff]

The NSIDC 0731 data does include a dT GeoTIFF that gives the time offset between the nominal mid-moth date and the actual date of each pixel. The GRASS Temporal Framework provides time stamp and time span options for each raster, not for each pixel. Each day could have a mostly-null raster?