There are many agencies in the US that use the Internet to distribute their Geographic Information System (GIS) data sets. The original, and still the most common, model for doing this is to have a web page with a list of your data sets and links for downloading them. The Montana State Library has had such a page since 1994, at http://nris.mt.gov/gis/datalist.html.

Some problems with this method are that it may be difficult for users to find the various web pages offered by GIS data source agencies, each data list has its own look and feel, and there is no incentive for agencies with pages like this to adhere to a metadata standard for describing their data.

The Federal Geographic Data Committee (FGDC) completed a metadata standard for describing GIS data in 1994 and offered the GIS community a new, metadata-driven, clearinghouse for making their data available. The agencies were offered free software to catalog their FGDC-compliant metadata and provide an index of it as a web service. The FGDC created a web site where users could formulate a query which would then be sent out to all of the agency index services. There turned out to be several problems with this method. First, it was difficult for agencies to monitor their index services, and these were frequently down. Second, the central search page was frustratingly slow if a query was sent out to a large number of servers. So the page was modified so that you could pick the servers your query would be sent to, but the list of servers was very long, and picking the servers to search was more trouble that most users wanted to go through.

The FGDC has moved on to a new model, where all of the metadata records agencies wish to publish are collected on a central server, and agencies are offered multiple options for submitting their metadata. The central repository, at http://geodata.gov, is a highly functional site that allows GIS users and non-GIS users easy access to the data sets they discover when they search there.

The Montana State Library participated in the original FGDC clearinghouse and makes its metadata catalog available at geodata.gov. But the Montana GIS community feels that it is still too difficult for users to find data about Montana there. Because of the way some agencies outside of Montana choose to structure their data catalogs, most searches for Montana data at geodata.gov return hundreds or thousands of irrelevant results, and the data that Montana agencies provide are quite difficult to find.

The State of Montana has chosen to support a new GIS Portal for Montana data, at the State Library, that will have similar functionality to the geodata.gov site, but will be more strongly moderated to make it easier for people to find high-quality data about Montana. The prototype for this site is running at http://gisportal.mt.gov. The Data Categories section will provide a list of the most important and frequently-requested data layers. The search functions and the capabilities of the results page will be nearly identical to the geodata.gov site.

A continuing problem with this will be balancing the desire to make archival and special-interest data sets available on the site against the desire to return a limited set of useful results to the user when they do a search. We will examine various strategies, such as some method to make the search engine push certain pre-selected data sets to the bottom or top of the results list, or allowing the user to suppress the display of limited-interest data.

The GIS Portal software provides a map viewer that allows map services discovered in the search results to be viewed as an interactive map. This is a great feature, but the current state of map services makes the good use of this feature difficult. Many data layers are buried in a long list of layers provided by a map service, and it can be difficult to find the layer you just clicked on when the service comes up in the map. We hope to solve this by creating a new map viewer that can accept a request from the portal to load a map service and turn on the specified layer.