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I have a OSM file (http://download.geofabrik.de/europe/malta-latest.osm.pbf). I am only interested in data that are around ramps (motorway_link,trunk_link,primary_link,secondary_link,tertiary_link) as in the picture. Therefore I want to preprocess the data to keep the OSM file as small as possible. I use the osmium tool.

I want to do it as followed, but I do not know how to implement step 2:

  1. Filter pbf file by desired tags -> malta-ramps.osm.pbf
osmium tags-filter -v --overwrite -o malta-ramps.osm.pbf malta-latest.osm.pbf w/highway=motorway_link,trunk_link,primary_link,secondary_link,tertiary_link
  1. Create polygons around the filteres data -> malta-polygons.poly
How to create the buffered polygons around the ramps e.g. with python?
  1. Cut out the polygons from the original OSM file -> malta-finished.osm.pbf
osmium extract --overwrite -p malta-polygons.poly -o malta-finished.osm.pbf malta-latest.osm.pbf

enter image description here

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    here an approach: convert lines to GeoJSON ogr2ogr -f GeoJSON lines.geojson malta-ramps.osm.pbf lines - compute a buffer ogr2ogr -f GeoJSON buffer.geojson lines.gpkg -dialect sqlite -sql "select st_buffer(geom, 0.0001) from lines" NOTE the buffer distance is in degrees, which is quite hacky. To use metric distance you need to transform to a metric CRS like UTM. Then you might union the buffered polygons to prevent overlap. Finally convert the polygons to a format osmium understand as describe here osmcode.org/osmium-tool/…
    – Jakob Miksch
    Nov 15, 2022 at 21:54

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I solved it like this:

  1. Convert from pbf to geojson -> malta-ramps.geojson
    osmium export malta-ramps.osm.pbf -o malta-ramps.geojson -O

  2. Extract unioned polygons (for all geometries) -> malta-polygons.geojson
    ogr2ogr -f GeoJSON malta-polygons.geojson malta-ramps.geojson -dialect sqlite -sql "select st_union(st_buffer(geometry, 0.002)) from malta-ramps"

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    Keep in mind, that buffering with latitude/longitude is super hacky and might only work for your area of interest. It would be much cleaner to reproject your data to metric system (e.g.UTM) first. Something like: ogr2ogr -t_srs EPSG:32632 malta-ramps-utm.geojson malta-ramps.geojson , Union with st_buffer(geometry, 100) with 100 meters, convert it back to lat/lon ogr2ogr -t_srs EPSG:4326 final_result.geojson malta-ramps-buffer.geojson moreover, the shape of the result should be much more circular and less ellipse shaped
    – Jakob Miksch
    Dec 3, 2022 at 14:40

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