To avoid discontinuous transportation lines between zooms 9 and 11.
- Originally limit geometry by length for z9 - z11 (`ST_Length(geometry) > ZRes(11)`)
- highway z9 to z11 was generalized during import-osm
- now just create a filtered and generalized z11 table
- then merge segments in the same way as from (full-featured) osm_highway_linestring and used this merged z11 for mat.view z10 and z9
Close#1107
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