Data.gov Adds Geoviewer

Today, Data.gov added a new capability to its growing arsenal of tools that allow for using the data the website makes accessible. The so-called Data.gov GEO Viewer has some interesting capabilities:

• Data loaded into viewer in Real-time through web URLs – the viewer downloads data directly from the authoritative source. An ArcGIS Server Geoprocessing service uncompresses data if needed (.zip, .gz, .tar), transforms data to JSON, and streams this back to the flex viewer.
• The GEO Viewer loads data in Web Mercator (if data or service supports it).Otherwise the GEO Viewer changes its basemap projection to Geographic Coordinate System and loads the data.
• The viewer supports the following data types:
• Map Services: OGC WMS, ArcGIS
• Feeds: GeoRSS
• Files: KML/KMZ, Shapefile
• The GEO Viewer allows for mashing up multiple datasets, map services, and feeds in one view. It supports basic navigation using the keyboard (without the need to use the "shift+alt+F7+drag the mouse+release alt and mouse button at the same time"-like features...).
• Set a basic color for the added data layer, set transparency for the layers, and use a swipe/see-through feature.
• Basic identify operation on the added data.
• Switching the basemap.

There are some limitations with this viewer, most of which are due to the fact that it downloads data from the source every time someone wants to see it:

• File size limit of 10MB – Shapefiles and KML files can have large compression ratios. While the registered file in Data.gov may be an under 10MB KMZ file, this can easily expand into a 100MB KML that then is streamed as JSON features to the client. This simply takes time.
• The information about the files is not enough to make an upfront assessment of whether the file is viewable or not. Almost every file in Data.gov is a .zip file. The GEO Viewer has to determine if it's dealing with an Esri Shapefile, OGC KML, Arc/Info Export (e00, remember these?), Microsoft Excel, CSV, or whatever format(s) until after it downloads the file. The metadata in neither raw data catalog nor geodata catalog includes this information. A result is that sometimes users will only be notified that the file type is not supported until after the viewer is launched.
• Registration of content is not readily usable by an application (James Fee found one of these...). There are several registrations of content that link to web pages or web applications, rather than the actual data. In this case, the content is however also available as an ArcGIS Server Map Service (although that's not in the registration in Data.gov).

 Are we there yet?

No. This GEO Viewer is not the end point. It's another step towards allowing users to interact and understand the data discoverable through Data.gov. The viewer illustrates the need to include more map services in Data.gov. Even registering map services alone may not be enough. In this world of service architectures, platforms, and such, we become more and more dependent on each other. Offering a service means signing up to a responsibility to keep this service running and available for an extended period of time.


Oh! And the proof of the pudding is in the eating! Here some samples:

1. My most favorite dataset on Data.gov: the locations and characteristices of world copper smelters.
2. For the patient folks: Active Mines and Mineral Plants in the US
3. My next house location: Geophysical Surveys of Bear Lake, Utah-Idaho
4. The dataset James was looking for: USGS Oil and Gas Assessment Database

Give it a whirl and provide your feedback to Data.gov.

Accessing the Data.gov catalog through an open interface

In its first year, Data.gov has grown from 47 datasets to over 270,000 datasets. These datasets aren’t actually hosted at Data.gov. The government agencies making these datasets available, host the files (or web services), and share them with the community through data.gov. But how did these datasets become discoverable at Data.gov?

Actually, the datasets are registered with Geodata.gov, a national catalog of geospatial resources that has been around for some 7 years and that “serves as a public gateway for improving access to geospatial information and data under the Geospatial One-Stop E-Government initiative”.

Geodata.gov provides access to almost 400,000 geospatial resources from over 300 partner collections from federal, state, and local government, as well as academia and commercial providers. Rather than having to sift through as many web sites, users can go to Geodata.gov and perform searches there. Creators of the geospatial resources can register this content with Geodata.gov if they choose to do so.  From its inception Geodata.gov has aimed to be inclusive in the sense that it doesn’t matter what geospatial technology you use to create or consume geospatial data (or web services) in order to use Geodata.gov or its content.

This design principle of being open and interoperable applies not only to the content but to the site itself as well. Since its launch Geodata.gov has provided a search interface following the Open Geospatial Consortium (OGC) Catalog Service for the Web (CS-W) specification. Later geodata.gov added a RESTful interface that returns search results as GeoRSS, KML, HTML, and GeoJSON. These interfaces are intended to support using the content registered with Geodata.gov without using the website.

The RESTful interface has been used by the Carbon Project to develop a desktop widget that allows for content discovery on Geodata.gov directly on your windows desktop, as well as developers who have extended tools like NASA’s World Wind. ESRI has developed clients for ESRI’s ArcGIS Desktop and Explorer that use the CS-W interface to provide its users with data discovery capabilities. All these are free tools intended to help bring the content registered in Geodata.gov to the users.

So what does this have to do with Data.gov? Well, when Data.gov was in search for content (pun intended), it was just common sense to reuse the effort already put in a catalog of geospatial content: Geodata.gov. Since June 2009, Data.gov has been using the CS-W interface provided by Geodata.gov.

Federal agencies can mark the content they have registered with Geodata.gov for sharing with Data.gov. It is this subset that is discoverable in the Geodata Catalog on Data.gov and you can search this subset using the interfaces mentioned before, allowing you to build your own discovery clients to the content available in the Geodata Catalog of Data.gov and include spatial searching, advances filtering, etc. Features that are not (yet) available at Data.gov itself.

How? In the RESTful interface, simply adding the parameter isPartOf=data.gov will filter Geodata.gov for content that has been marked for sharing with Data.gov. A request for orthoimagery that is discoverable through the Geodata Catalog in Data.gov thus becomes:

http://geo.data.gov/geoportal/rest/find/document?isPartOf=data.gov&searchText=orthoimagery&f=html

Doing this in the CS-W interface means creating an OGC CS-W request like this:

<csw:GetRecords xmlns:csw="http://www.opengis.net/cat/csw/2.0.2" xmlns:ogc="http://www.opengis.net/ogc" xmlns:ows="http://www.opengis.net/ows" version="2.0.2" service="csw" xmlns:dc="http://purl.org/dc/elements/1.1/" resultType="results"> 

  <csw:Query typeNames="csw:Record">

    <csw:ElementSetName>summary</csw:ElementSetName>

    <csw:Constraint version="1.1.0">

      <ogc:Filter xmlns:ogc="http://www.opengis.net/ogc">

        <ogc:And>

          <ogc:PropertyIsLike wildCard="%" escape="" singleChar="">

            <ogc:PropertyName>AnyText</ogc:PropertyName>

            <ogc:Literal>isPartOf:data.gov</ogc:Literal>

          </ogc:PropertyIsLike>

          <ogc:PropertyIsLike wildCard="%" escape="" singleChar="">

            <ogc:PropertyName>AnyText</ogc:PropertyName>

            <ogc:Literal>orthoimagery</ogc:Literal>

          </ogc:PropertyIsLike>

        </ogc:And>

      </ogc:Filter>

    </csw:Constraint>

  </csw:Query>

</csw:GetRecords>

More details on these interfaces to use the content of Geodata.gov and Data.gov’s Geodata Catalog is available in the API Documentation.

Whether you want to use the RESTful interface or prefer the CS-W + XML approach, the content in Data.gov and Geodata.gov is yours to discover. Use that content to make a nice map or two. Please don’t use it to plan your strategy to take over the world.