Canadian Geospatial Data Infrastructure Interoperability Pilot

Overview

Compiling a Canadian national dataset for layers such as roads and placenames is a challenge because source data is maintained independently by 13 provinces and territories, all using different data schemas and technologies. Previously, maintaining the national dataset involved copying and merging large datasets which are updated daily and have different schemas.

The Canadian Geographic Data Infrastructure Interoperability Pilot (CGDIIP) connects all provincial and territorial datasets, making them accessible through one national GeoBase portal. The CGDIIP ensures up-to-date data is accessible in real time as one national dataset while ensuring data is updated at source by data custodians.

Integration is achieved by standardising on a national data schema and using open standards from the Open Geospatial Consortium (OGC) to connect source datasets.
Data feedback is collected from a community of users who provide updates against the national dataset. Updates are routed to the correct data custodian for review and incorporation into the source database, ensuring data is maintained closest to source.

For this project, LISAsoft developed powerful browser clients to search for map layers, build maps, submit geographic feature updates and view changes. LISAsoft also extended GeoServer, a Web Feature Server, to support the cascading queries required to access multiple datasets at once.

Standards used include:

Web Feature Services (WFS), including transactions and cascading

Web Map Services (WMS) map layers for visualisation

Catalogue Service for the Web (CS/W) for search and discovery

OWS Context to store maps

GML to export layers

The following spatial infrastructure was put in place:

Web services at each Province. Each province installed a Web Feature Service (WFS) and Web Map Service (WMS).
Data is updated close to source by expert data custodians in the Provinces.
A common national schema is used for each data layer.
An aggregating WFS and WMS provides a seemless national data coverage for users.

The pilot addressed the following use cases:

Use Case 1: Demonstrates distributed and cascaded access to provincial framework data servers

Users can search for WMS and WFS layers using a browser interface to a Catalog.
Selective GML datasets can be downloaded using spatial filters from browser and desktop clients.
Users can build and share maps between applications.

Use Case 2: Demonstrates a feedback and update workflow for the distributed servers

The workflow for updating data involves:

User sketches a feature and enters attributes.
User saves the suggested change into a Feedback Feed.
The province data custodian reviews entries from the Feedback feed, then copies or rejects the updates in the province database. A second event is sent into the Update Notification Feed.
The User does a side-by-side comparison of their suggested and custodian’s update event.

GeoRSS is used to store and publish geospatial events.

Use Case 3: Geographic event notification

An emergency preparedness scenario was used involving a toxic gas plume analysis and evacuation notification.

A time series toxic plume was loaded as GML, analyzed then stored in a GeoRSS event feed. The GeoRSS list of events can then be visualized in a web browser.

Software Components

A number of software components were developed as part of this project.

Web Client

A MapBuilder based web client, developed by LISAsoft, was built to incorporate the following technology:

Catalog (CSW2) client to allow the search and discovery of datasets known to the central server.
GeoRSS feed readers to allow the user to subscribe to and monitor the data update feeds from both the data users and data custodian.
WFS-T to allow the creation, update and deletion of features to be published to the update feed along with associated metadata, as well as allowing the visualisation of both the services and the update feeds.

Thick Client

Two thick clients were provided by The Carbon Project.

CarbonArc

CarbonArc is an extension to ESRI ArcGIS that provides discovery, consumption and interaction capabilities for the OGC Spatial Data Infrastructure (SDI) 1.0 baseline. A plugin was created for CarbonArc to include the GeoRSS capabilities needed for review, revision and acceptance/rejection of the feature changes.

GAIA

GAIA is a Windows application for accessing, visualizing and sharing location content. GAIA is currently available as a free download.

Aggregating WFS

Two WFS servers were customised to function as Aggregating WFS services; GeoServer was extended by LISAsoft, and CubeSERV WFS by CubeWerx. These servers received requests from client applications and redirected them to each of the Provincial and Territorial servers. It then collected, merged and returned the responses to the client.

WFS GeoRSS feed

Extensions were developed for CubeSERV WFS (by CubeWerx) and GeoServer (by LISAsoft) to provide the required GeoRSS publishing capabilities to the services. This allowed the WFS server to track and publish change requests for the data custodian, as well as tracking the results of the change requests for the data users.

Credits

The CGDI-IP is coordinated by Geoconnections, the sponsor of the Canadian national Spatial Data Infrastructure.
The pilot has been run as part of an Open Geospatial Consortium (OGC) testbed in partnership with the OGC.
The Australian Corporate Research Center for Spatial Information (CRC-SI) part sponsored LISAsoft’s involvement in order to bring Standards based Spatial Infrastructure expertise back into Australia.
Canadian Provinces (equivalent to Australian States) deployed WFS and WMS servers.
Technology has been developed and part sponsored by industry (LISAsoft in Australia, Cubewerx and The Carbon Project).
Provincial services provided by Galdos, Sunertek, and Cubewerx.

Additional Info

Visit the OGC CGDI page.
Download the Webcast (341MB, wmv) presented on Nov 30th, 2007 from Ottawa, Canada
Download the presentation slides (3MB, ppt) from the Australian webcast.