How to Use a KML Feature Extractor for GIS Workflows

KML Feature Extractor: Convert KML Layers to CSV, GeoJSON, and Shapefile

What it does

• Extracts features (Placemarks: points, lines, polygons) from KML files.
• Converts geometry and attribute data into common GIS formats: CSV (coordinates + attributes), GeoJSON (feature collection), and Shapefile (ESRI-compatible vector).

Key capabilities

• Preserves geometry types: points, LineStrings, Polygons, multi-geometries.
• Exports attributes from KMLand fields into table columns.
• Handles coordinate transforms (e.g., WGS84 to other projections) if needed.
• Batch processing of multiple KML files or layered KML with folders/styles.
• Optionally flattens nested folders or preserves folder/group names as an attribute.

Workflow (steps)

1. Load KML file(s).
2. Detect features and geometry types.
3. Parse attributes: name, description, ExtendedData key–value pairs.
4. Normalize geometries (e.g., multi → single with grouping ID if required).
5. Choose output format:
   • CSV: write one row per feature; include geometry as lon/lat (point) or WKT/coordinate string for lines/polygons.
   • GeoJSON: output FeatureCollection with geometry objects and properties.
   • Shapefile: write .shp/.shx/.dbf (note DBF field name/type limits).
6. Optionally reproject coordinates and validate geometries.
7. Save/export with metadata and log of any skipped features.

Format-specific notes

• CSV
  • Best for point datasets or small line/polygon exports using WKT or coordinate strings.
  • No native geometry type—include lon/lat columns for points or a WKT column.
• GeoJSON
  • Preserves full geometry and properties; ideal for web mapping.
  • Supports nested properties and multi-geometries.
• Shapefile
  • Widely supported in desktop GIS; splits into multiple files.
  • DBF limits: 10-character field names, limited data types; long strings may be truncated.
  • Only one geometry type per shapefile (mixing points/lines/polygons requires separate files).

Common pitfalls and how to avoid them

• Mixed geometry types — split into separate outputs per type.
• Large coordinate precision or very large files — stream-processing or chunking recommended.
• Attribute name collisions or illegal DBF names — sanitize and truncate field names for Shapefile.
• HTML in — strip or parse HTML to extract useful text.
• KML styles and icons — these aren’t directly supported in Shapefile/CSV; export style info as properties if needed.

Tools and libraries (examples)

• GDAL/ogr2ogr — robust command-line tool for direct conversion: ogr2ogr -f GeoJSON out.json in.kml
• Python: fastkml, simplekml, pyKML, shapely, Fiona, geopandas for parsing and export.
• QGIS — GUI-based import/export with reprojection and layer handling.
• Online converters — convenient for small files but watch privacy and file size limits.

Example ogr2ogr commands

• KML → GeoJSON:

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  ogr2ogr -f “GeoJSON” output.geojson input.kml 

• KML → Shapefile (split by geometry):

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  ogr2ogr -f “ESRI Shapefile” output_shp input.kml -nlt PROMOTE_TOMULTI 

• KML → CSV (points as lon/lat):

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  ogr2ogr -f CSV output.csv input.kml -lco GEOMETRY=AS_XY