GML Validator
Validate a GML file for XML schema compliance, geometry encoding, and spatial reference system definitions.
Upload a GML (Geography Markup Language) file to verify its XML schema validity and spatial data integrity. The GDAL validator inspects GML namespace declarations, geometry encoding (gml:Point, gml:LineString, gml:Polygon, gml:MultiSurface), spatial reference system attributes (srsName), and feature type structure. Layer names, feature counts, and detected SRS information are reported.
Drag file here to validate, or select file
Supported: .gml • Max 50MB
What We Validate
- Well-formed XML and valid GML namespace declarations
- Geometry element encoding (gml:Point, gml:LineString, gml:Polygon, gml:MultiSurface)
- srsName attribute presence and EPSG code format
- Feature type names and attribute field schemas
- Coordinate tuple dimension consistency (2D vs 3D coordinates)
- Feature counts per detected geometry layer
Common Issues Detected
- Missing or incorrect GML namespace URI in the root element
- Geometry elements referencing undefined or missing SRS identifiers
- Mixed 2D and 3D coordinate tuples within the same geometry
- Feature type schemas with conflicting attribute definitions
- Large German cadastral GML (ALKIS NAS) using custom extensions unsupported by basic parsers
Frequently Asked Questions
Which GML versions are supported?
The GDAL validator supports GML 2.x and GML 3.x formats, including GML 3.2.1. Highly customised schemas like ALKIS NAS may require specific GDAL drivers compiled with libxml2 support.
My GML file has an unknown SRS — what does that mean?
An unknown SRS means the srsName attribute either references an EPSG code not registered in the GDAL projection database, or uses a non-standard CRS URI format. Geometry data can still be read, but spatial accuracy cannot be guaranteed.
Why does the validator report fewer features than expected?
This typically occurs when feature elements use non-standard tag names that GDAL does not automatically detect. Ensure your GML root uses standard featureMember or featureMembers wrappers.