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The GeoPackage specification is designed to be extensible. Extensions allow implementors to add capabilities — new table types, spatial indexes, styling, metadata, and more — while still producing valid GeoPackage files. Each extension is declared in the gpkg_extensions system table so that any conformant reader knows which extensions are in use.

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How Extensions Are Registered

Every extension registers one or more rows in the gpkg_extensions table. A row captures:
  • table_name – the table the extension applies to (or NULL for a file-level extension)
  • column_name – the specific column affected (or NULL)
  • extension_name – a namespaced identifier in the form author_name (e.g. gpkg_rtree_index, nga_feature_style)
  • definition – a URL pointing to the extension specification
  • scope – either read-write or write-only
Readers that encounter an unknown read-write extension should treat the file as potentially invalid for their use case. write-only extensions can be safely ignored by read-only consumers.

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Managing Extensions

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ExtensionManager

ExtensionManager is the central coordinator for all GeoPackage extensions. It delegates to registered ExtensionManagement implementations and handles bulk operations like deleting or copying all extensions for a table. 
import { GeoPackageAPI } from '@ngageoint/geopackage';

const geoPackage = await GeoPackageAPI.open('my.gpkg');
const extensionManager = geoPackage.getExtensionManager();

// Delete all extensions associated with a table
extensionManager.deleteTableExtensions('my_features');

// Copy all extensions from one table to another
extensionManager.copyTableExtensions('my_features', 'my_features_copy');

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NGAExtensions

NGAExtensions manages the suite of community extensions developed by the National Geospatial-Intelligence Agency (NGA). It is automatically registered with ExtensionManager and handles the geometry index, tile scaling, feature styles, contents ID, and feature-tile link extensions. 
import { NGAExtensions } from '@ngageoint/geopackage';

const nga = new NGAExtensions(geoPackage);

// Delete all NGA extensions for a specific table
nga.deleteTableExtensions('my_features');

// Delete all NGA extensions from the entire GeoPackage
nga.deleteExtensions();
NGA extensions are community extensions and use the author prefix nga_. They are not part of the core OGC GeoPackage specification but are widely supported.

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Available Extensions

RTree Spatial Index

OGC extension (gpkg_rtree_index). Stores a SQLite R*Tree virtual table for fast bounding-box spatial queries on feature geometry columns.

Related Tables

OGC community extension (gpkg_related_tables). Defines many-to-many relationships between any two GeoPackage tables using mapping tables and an gpkgext_relations catalog.

Feature Style

NGA extension (nga_feature_style). Associates visual style rules (color, width, fill, icons) with feature tables and individual feature rows for rendering.

Metadata

OGC extension (gpkg_metadata). Attaches structured metadata documents (ISO 19115, Dublin Core, etc.) to the GeoPackage, individual tables, columns, or specific rows.

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Additional NGA Extensions

ExtensionAuthorDescription
Geometry IndexngaAlternative geometry index stored in GeoPackage extension tables (nga_geometry_index). Useful when SQLite RTree is unavailable.
Contents IDngaAssigns stable integer IDs to GeoPackage contents entries for use by other extensions.
Tile ScalingngaConfigures zoom-level scaling strategies for tile layers.
Feature-Tile LinkngaLinks feature tables to corresponding tile tables for coordinated rendering.
PropertiesngaStores key-value property metadata about the GeoPackage itself.
SchemagpkgDocuments column-level metadata including data types, constraints, and human-readable names via gpkg_data_columns.
CRS WKTgpkgAdds Well-Known Text (WKT) representations for coordinate reference systems beyond those built into the core spec.

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