Extension Title

Feature Tile Link

Introduction

This extension creates a link between a feature and tile table. A tile table containing tiles that represent or were generated from features can be linked to the feature table. The link enables feature queries when dealing with tiles representing features.

Extension Author

National Geospatial-Intelligence Agency, author_name nga

Extension Name or Template

nga_feature_tile_link

Extension Type

New Requirement

Applicability

This extension applies to the table names of feature user tables (2.1.6) and tile user tables (2.2.8).

Scope

Read-write

Requirements

GeoPackage

Extension Table Entry

The Geometry Index extension is registered into the gpkg_extensions table only once as follows:

gpkg_extensions
table_name column_name extension_name definition scope

null

null

nga_feature_tile_link

URL to this extension description

read-write

Feature Tile Link Table

The Feature Tile Link Table contains a user feature table and tile table name for linked tables.

nga_feature_tile_link
Column Name Type Description Null Default Key

feature_table_name

TEXT

Feature user data table name

no

PK

tile_table_name

TEXT

Tile user data table name

no

PK

CREATE TABLE nga_feature_tile_link (
  feature_table_name TEXT NOT NULL,
  tile_table_name TEXT NOT NULL,
  CONSTRAINT pk_nftl PRIMARY KEY (feature_table_name, tile_table_name)
);

GeoPackage SQLite Configuration

None

GeoPackage SQLite Extension

None

Examples

The rivers GeoPackage has a rivers feature table linked to a rivers_tiles tile table. The tiles were generated from the features for zoom levels 0 through 6.