Merge branch 'main' of github.com:alifeee/blog

2024/12/hitchhiking/README.md

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+# Hitchhiking
+
+Leaflet:
+
+- <https://leafletjs.com/examples/geojson/>
+- <https://leafletjs.com/examples/layers-control/>
+
+How to generate files:
+
+```bash
+## install required tools
+# for ogr2ogr (convert between gpx and geojson)
+sudo apt install gdal-bin
+
+# single conversion
+ogr2ogr 1-london-ferrybridge.geojson 1-london-ferrybridge.gpx tracks
+
+# make gpx tracks using https://map.project-osrm.org/
+# multiple GPX files in a `gpx` folder (towards a `geojson` folder)
+while read file; do bn=$(basename "${file}"); filegj=$(echo "${bn}" | sed 's/\.gpx/.geojson/g'); ogr2ogr "geojson/${filegj}" "${file}" tracks; done <<< $(find gpx/ -type f)
+# add file to geojson files as a property of the first feature
+while read file; do fname=$(basename "${file}"); cat "${file}" | jq '.features[0].properties.label = "'"${fname%.*}"'"' | sponge "${file}"; done <<< $(find geojson/ -type f)
+# add trip number as a property
+while read file; do fname=$(basename "${file}"); cat "${file}" | jq '.features[0].properties.trip = "'"$(echo "${fname}" | sed -E 's/(^[0-9]*)\..*/\1/')"'"' | sponge "${file}"; done <<< $(find geojson/ -type f)
+# combine geojson files
+
+while read file; do cat "${file}"; done <<< $(find geojson/ -type f | sort -t / -k 2 -n) | jq --slurp '{
+    "type": "FeatureCollection",
+    "name": "hitchhikes",
+    "features": ([.[] | .features[0]])
+}' > hitching.geojson
+```
+
+turn some text into a json-compatible string:
+
+```bash
+getclip | tr '\n' '~' | sed 's/~/<br>/g' | sed 's/"/\\"/g' | setclip
+```