extension_crs_wkt.adoc

WKT for Coordinate Reference Systems

Introduction

The OGC GeoPackage standard was adopted prior to the adoption of "OGC Well known text representation of Coordinate Reference Systems" [34], in 13 August, 2014. As a result, the OGC GeoPackage standard references an older document [32] which has known ambiguities that are being encountered in the field. This extension establishes a new column to contain values that conform to the new standard.

Extension Author

GeoPackage SWG, author_name gpkg.

Extension Name or Template

gpkg_crs_wkt

Extension Type

Extension of Existing Requirement in clause [spatial_ref_sys_data_table_definition].

Applicability

Applies to the gpkg_spatial_ref_sys table.

Scope

Read-write

Requirements

Table

Table Definition

Requirement 115

For GeoPackages conforming to this extension, the gpkg_spatial_ref_sys table SHALL have an additional column called definition_12_063 as per Spatial Ref Sys Table Definition and gpkg_spatial_ref_sys Table Definition SQL (CRS WKT Extension).

Table 1. Spatial Ref Sys Table Definition

Column Name	Column Type	Column Description	Not Null	Default	Key
srs_name	TEXT	Human readable name of this SRS	yes
srs_id	INTEGER	Unique identifier for each Spatial Reference System within a GeoPackage	yes		PK
organization	TEXT	Case-insensitive name of the defining organization e.g. EPSG or epsg	yes
organization_coordsys_id	INTEGER	Numeric ID of the Spatial Reference System assigned by the organization	yes
definition	TEXT	Well-known Text [32] Representation of the Spatial Reference System	yes	'undefined'
description	TEXT	Human readable description of this SRS	no
definition_12_063	TEXT	Well-known Text [34] Representation of the Spatial Reference System	yes	'undefined'

Table Data Values

Requirement 116

Values of the definition_12_063 column SHALL be constructed per the WKT syntax in [34].

Requirement 117

At least one definition column SHALL be defined with a valid definition unless the value of the srs_id column is 0 or -1. Both columns SHOULD be defined. If it is not possible to produce a valid [32] definition then the value of the definition column MAY be undefined. If it is not possible to produce a valid [34] definition then the value of the definition_12_063 column MAY be undefined.

If, for a particular row, both the definition and definition_12_063 columns are populated, the value in the definition_12_063 column takes priority.

Abstract Test Suite

Table Definition

Table Definition

Test Case ID	/extension_crs_wkt/table_def
Test Purpose	Verify that the gpkg_spatial_ref_sys table exists and has the correct definition. Extends /base/core/gpkg_spatial_ref_sys/data/table_def.
Test Method	PRAGMA table_info('gpkg_spatial_ref_sys') Fail if returns an empty result set Fail if result set does not include a column named 'definition_12_063' or if the column is not of type 'TEXT', notnull 1, and dflt_value 'undefined'. Pass if no failures.
Reference	Annex F.10 Req 115
Test Type	Basic

Table Data Values

Test Case ID	/extension_crs_wkt/data_values_default
Test Purpose	Verify that the gpkg_spatial_ref_sys table contains the required default contents. Extends /base/core/gpkg_spatial_ref_sys/data_values_default.
Test Method	SELECT organization, organization_coordsys_id, definition, definition_12_063 FROM gpkg_spatial_ref_sys WHERE srs_id = -1 Confirm that this returns "NONE" -1 "undefined" "undefined" SELECT srs_id, organization, organization_coordsys_id, definition, definition_12_063 FROM gpkg_spatial_ref_sys WHERE srs_id = 0 Confirm that this returns "NONE" 0 "undefined" "undefined" SELECT definition FROM gpkg_spatial_ref_sys WHERE organization IN ("epsg","EPSG") AND organization_coordsys_id 4326 Confirm that this is a valid CRS SELECT definition_12_063 FROM gpkg_spatial_ref_sys WHERE organization IN ("epsg","EPSG") AND organization_coordsys_id 4326 Confirm that this is a valid 12-063 CRS Pass if tests 1-4 are met Fail otherwise
Reference	Annex F.10 Req 116
Test Type	Capability

Test Case ID	/extension_crs_wkt/data_values_required
Test Purpose	Verify that the spatial_ref_sys table contains rows to define all srs_id values used by features and tiles in a GeoPackage. Extends /base/core/gpkg_spatial_ref_sys/data_values_required.
Test Method	SELECT definition, definition_12_063 FROM gpkg_spatial_ref_sys WHERE srs_id NOT IN (0, -1) For each result Fail if both definition values are 'undefined' Pass if no failures
Reference	Annex F.10 Req 117
Test Type	Capability

Table Definition SQL

gpkg_spatial_ref_sys

gpkg_spatial_ref_sys Table Definition SQL (CRS WKT Extension)

CREATE TABLE gpkg_spatial_ref_sys (
  srs_name TEXT NOT NULL,
  srs_id INTEGER NOT NULL PRIMARY KEY,
  organization TEXT NOT NULL,
  organization_coordsys_id INTEGER NOT NULL,
  definition  TEXT NOT NULL DEFAULT 'undefined',
  description TEXT,
  definition_12_063 TEXT NOT NULL DEFAULT 'undefined'
);