Martijn Brunink enhanced the Amsterdam spatial data schema by delivering a Terrain Schema Enhancement in the Amsterdam/amsterdam-schema repository. He focused on improving the validation, accuracy, and consistency of terrain-related attributes, addressing data quality for GIS analytics and downstream products. Using SQL and applying skills in data modeling and database schema design, Martijn updated validation rules and tests to support the new schema changes, ensuring maintainability and efficient validation cycles. His work demonstrated a disciplined approach to version control and targeted, high-impact schema modifications, resulting in more reliable structuring of geographical and land-use information within the Amsterdam spatial data ecosystem.