New answers tagged spatial-index
If the linestring are indeed along the same x but vary on y you can create indices on ST_YMAX() and ST_YMIN() functions like so: CREATE INDEX idx_ymin_ymax ON places (St_ymax(geom),St_ymin(geom)); Next just query the table using St_ymax and St_ymin in the WHERE clause to limit the results.
I would start by manually labeling the pixels in an entire scene that are vs are not part of your desired landuse. Then you could try various predictive model formalizations to build models that predict the marked pixels, keeping the model that gives the best results. (There is an entire field of techniques called "model selection" that helps do this ...
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