Chapter Five     |     Context and Rationale     |     Organisational Approach     |     Implementation Approach

Organizational Approach

Web based mapping provides the functionality to help discover and visualize spatial information referenced from Catalog Service Systems. A Catalog Service System (described in Chapter 4) is implemented through Internet-based software that allows users to inventory, advertise, and access metadata and associated geospatial information within a global framework of servers. Figure 5.1 shows one scenario of a client accessing a Catalog (actually the catalog implements a Service Registry) to discover data and web mapping services and then requesting and displaying maps from different servers.

Figure 5.1 : Interaction of web map client with catalog and map servers

Figure 5.1 : Interaction of web map client with catalog and map servers

A catalog service that provides only references to raw geospatial data would be of use to only GIS experts and their software. By making map displays of geospatial information, casual users can interact with and see spatial data that was previously only available to GIS experts.

Figure 5.2 shows one example of a user interface for a Catalog Service System. Many different GUIs can be built to provide special access for different categories of user. All the GUIs must use the same protocol agreements to interact with the map server software.

Figure 5.2

The Map Frame in figure 5.2 illustrates the value of specifying the bounding geometry (box or polygon) for the spatial part of the query for retrieval within the Catalog Service System. Typical dimensions for the query include spatial, temporal, paleotemporal and thematic values. The user also has the option to specify specific servers, or to search all registered servers for the geospatial data of interest.

The Map Frame can also be used for the presentation of the spatial component of the metadata in maps. The result presentation in a Catalog Service System can be installed as a hidden search variable for further processing, or as List or Map in a web browser for visual presentation. The resulting presentation should be within the bounding geometry that was specified by the user for the Spatial Query. Often users like to interact with the objects on the maps. They like to have links on an object in a map connect to its metadata and then use a link in the metadata to connect to the real data. This can be accomplished via the GetFeatureInfo interface of the Web Map Server specification.

The success of Web Mapping depends on the use of consistent metadata standards (See Chapter 3). Historically, there have been a great variety of metadata standards developed and implemented across communities. Thanks to the contributions of many mapping organizations worldwide, an ISO standard 15046 for metadata is being finalized this year. Over time, organizations will see the value of migrating to a consistent ISO metadata format so that consistent global scale search and access of geospatial data can occur to support on line mapping.

Map Servers

For the concept of Web Mapping to be successful, a near global, truly inter-connected series of map servers must be established through the use of common protocols whether it be in an intranet, an extranet, or an internet scenario. Figure 5.3 provides a notional view of such a server network. Servers supporting on line web mapping will be registered to a Catalog Service System as noted above.

Figure 5.3: Notional View of Web Mapping Server Network

Figure 5.3: Notional View of Web Mapping Server Network

Chapter Five     |     Context and Rationale     |     Organisational Approach     |     Implementation Approach