Running inference on areas that span several Sentinel-2 scenes.

[cholmes]

Right now the CLI tools operate within a single Sentinel 2 scene. Ideally users could supply a set of S2 scenes (to start) or a large area that spans a number of scenes (depends on #59 to help select the right scenes for a large area). An end goal for this work would be that a user could supply a geometry of a large area, like a state or small country, and the tools would make it super easy to generate a complete generated fiboa file for the entire area.

The baseline would be run it serially on a single system - running inference for each scene and then combining the results, into fiboa polygons. But ideally the tools would even make it easy to run this in parallel, so someone with access to a bunch of cloud credits or an HPC could generate results for large areas.