Technical Benefits:
Development of the GeoConferencing Service.

The GeoChat prototype, starting point for GeoConference software development.

Challenges:
New technology to be developed

Consultants TGIS entered the GeoInnovations project with a working prototype, GeoChat, which demonstrated how Internet conference participants could make use of shared, georeferenced pointers and annotations in a geoconference.

Since GeoChat was designed as a demonstration prototype, it had many limitations, including:

►      Copies of geodata and image layers used in the map background had to be present on each client computer.

►      Only one vector data type (proprietary) was available for the background map. JPEG was used for images in the background, which meant that a georeference header file had to created for it.

►      Consequently, the background layers were static, and there was no way to protect proprietary data.

►      From the point of view of a firewall, the conference client appeared to be a server, which meant that clients could not easily communicate from one network to another.

►      GeoChat conferences were ephemeral. They could not be saved and reused. Information that had been recorded as annotations or as text messages between conference participants was lost when the conference was ended.

These limitations were among the challenges to be resolved in the development of the GeoConferencing service.

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A session in the GeoConference demonstration client. Click here to see the full image.

The GeoConferencing Service

The central element of the GeoConferencing service is a shared, synchronized, georeferenced workspace. Conceptually, the workspace has two parts:

►      A background map of layers from a variety of georeferenced sources;

►      A foreground containing:

>        Georeferenced pointers controlled by session participants,

>        Labelled, georeferenced annotations (point symbols, lines and polygons).

The service also provides a text log (seen as a chat window) that can be used for time-stamped messages or findings and information (properties) about map layers, annotations and a list of participants in the session.

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Multi-Source Map Background

Participants in a GeoConference session see a view of the georeferenced workspace as map. The workspace contains layers from a variety of sources, including:

►      Web Map Services,

►      Shapefiles and

►      GeoTIFF files.

These sources can be local to the server, local to one of the participants, or elsewhere on the Internet. The architecture of the GeoConferencing Service makes the location of geodata extremely flexible.

How GeoConference server builds the map background:

The GeoConference server requests only the visible area (extent) of geoinformation layers from their sources. They are rendered, at the data source, in the resolution seen in the map window. The server combines the layers from the sources in the order requested by the client. It then sends the fused map as a set of compacted tiles to the geoconferencing client.

This method has several important advantages:

►      It is compatible with the OGC Web Map Service (WMS) and many other Internet map services.

►      No matter how large or complex the source data, only a small amount of rendered geoinformation is sent to the server and on to the conferencing client.

►      Proprietary data is protected; no geodata leaves the source location.

►      It is easy to add data connectors for new types of data sources as required.

In the case of WMS, the data connector need only formulate the map request properly. The WMS extracts the data and renders a map image. Since the WMS is a Web service, the connector can be local to the GeoConference server, local to the WMS, or in any third location.

The geoconferencing service uses the same connector architecture to access GeoTIFF and Shapefile geodata for the GeoConference. Consultants TGIS added components based on publicly available software libraries to access georeferenced map image as requested by the connector. The connector then represents the data as requested and sends it on to the GeoConference server as an image.

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Simplified architecture of the GeoConferencing Service. Elements in red were developed in the GeoInnovations project.

The connector architecture of the service is extremely flexible. Geospatial information can be located on a conference client computer, on the server host computer or elsewhere on the Internet.

Collaboration in a GeoConference

GeoConference participants control the map view and interact with each other through the GeoConference server. The server mediates control of shared elements (the view and its annotations. The server controls access to conference sessions and stores them for later continuation, review or reuse.

Users select map layers and symbology, zoom and pan the view, and control the size of the map window. The server immediately propagates changes to the view to all participants so that the real-time collaboration remains focused in the group discussion.

Map Pointers and Annotations

Each user controls a georeferenced map pointer he can use to clarify his statements and questions. All pointers can be active and visible at once.

Conference participants can annotate the workspace with georeferenced symbols, lines and polygons. Any conference participant can edit the geometry, symbology or properties of the annotations.

Communicating with the Server

The GeoConference server communicates with clients through either a proprietary TCP/IP interface or through a Web interface using SOAP over standard HTTP. A conference session can contain both types of connection concurrently. While somewhat slower than the proprietary connection method, the Web interface offers several benefits:

►      The geoconference crosses corporate firewalls more easily (connecting to the server is like connecting to a Web site).

►      The open interface permits development of a variety of customized clients.

►      Use of SOAP follows the trend in Web services development.

Development of a true HTTP-protocol client capable of real-time conferencing was one of the major challenges of the project.

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Detail from the Map window:

►User’s map pointers (red and blue arrows).

►Annotations “reef” (red hachured polygon) and shoreline (dashed purple line).

In the GeoConferencing client the Map tab of the Information Panel shows layers in the map, their sources and their properties (metadata and on-the-fly processing information.)

Technical Benefits for Geomatics

GeoConference permits geomatics specialists to communicate and discuss their geoinformation and expertise without traveling to meetings. It provides a channel through which they can support decision-makers in a real-time, question-and-answer format.

The georeferenced workspace allows the geospatial expert to combine his geospatial products with information from other specialists, from field observers, and from standardized geoinformation sources:

►      Cascading Web Map Services (such as provided by CubeWerx’ CubeSERV software), provide access to enormous quantities of geoinformation for use in the geoconference.

>        For example, GeoConference uses WMS to access the entire Canadian National Topographic Data Base (NTDB; the data behind the 1:50,000 and 1:250,000 map series) as rendered geoinformation from the WMS maintained by the Centre for Topographic Information in Sherbrooke, Québec.

>        GeoConference exploits the SLD features of WMS version 1.1.2+, which allows conference participants to access and choose among symbology options for WMS layers.

►      Shapefile format is one of the most widely-used ad hoc standards in the geomatics industry. GeoConference uses a publicly available software library to provide users with control over the symbology applied to Shapefile layers viewed in the map workspace.

►      GeoTIFF  format is supported by most remote sensing image processing software and by the OGC Web Coverage Service. The format conserves georeferencing information and is extremely flexible, allowing multiple bands, multiple bit depths, tiling, compression, colour tables, etc. When accessing GeoTIFF, GéoConférence can perform many on-the-fly manipulations:

>        Selection and combination of 8, 16 or 32-bit bands (assignment to RGB channels);

>        Several image enhancement operations;

>        Image filtering.

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