kml2geojson.sh

#!/usr/bin/env bash
set -ex

# Convert all KML files under the current directory to GeoJSON.
# Output is written under ./GeoJSON mirroring the KML directory structure.

if ! command -v ogr2ogr >/dev/null 2>&1; then
  echo "error: ogr2ogr not found. Install GDAL to use this script." >&2
  exit 1
fi

root_dir="$(pwd)"
out_root="${root_dir}/GeoJSON"

remove_if_empty() {
  local path="$1"
  if [ ! -f "${path}" ]; then
    return 0
  fi
  local count
  count="$(ogrinfo -ro -al -so "${path}" 2>/dev/null | awk '/Feature Count/ {print $3; exit}')"
  if [ -z "${count}" ] || [ "${count}" -eq 0 ]; then
    rm -f "${path}"
  fi
}

# Find all .kml files and convert each to GeoJSON by geometry type.
find "${root_dir}" -type f -name "*.kml" | while IFS= read -r kml_path; do
  rel_path="${kml_path#${root_dir}/}"
  out_base="${out_root}/${rel_path%.kml}"
  out_dir="$(dirname "${out_base}")"
  mkdir -p "${out_dir}"

  # Convert to GeoJSON, overwriting if it already exists.
  point_out="${out_base}_point.geojson"
  line_out="${out_base}_line.geojson"
  polygon_out="${out_base}_polygon.geojson"

  ogr2ogr -f GeoJSON "${point_out}" "${kml_path}" \
    -where "OGR_GEOMETRY='Point' OR OGR_GEOMETRY='MultiPoint'"
  ogr2ogr -f GeoJSON "${line_out}" "${kml_path}" \
    -where "OGR_GEOMETRY='LineString' OR OGR_GEOMETRY='MultiLineString'"
  ogr2ogr -f GeoJSON "${polygon_out}" "${kml_path}" \
    -where "OGR_GEOMETRY='Polygon' OR OGR_GEOMETRY='MultiPolygon'"

  remove_if_empty "${point_out}"
  remove_if_empty "${line_out}"
  remove_if_empty "${polygon_out}"

  echo "converted: ${rel_path} -> ${out_base#${root_dir}/}_{point,line,polygon}.geojson"
done