CIESIN Columbia University - World Data Center for Human Interactions in the Environment (WDC)

Internet Mapping of Global Data Sets
An increasing number of organizations are making global data accessible through Internet-based map services that permit online visualization of data and sometimes basic analysis and interactive access to data. Two categories of map services are currently available: some services provide access to data hosted locally through a “map server,” whereas others provide access to distributed data sources using open standards for data interoperability and access.

Selected Internet mapping services currently available include the following:

•SEDAC Map Viewer
•Google Earth
•NASA World Wind

The remainder of this page describes different approaches to Internet mapping.

Selected Map Servers Serving Global-Scale Data

Selected Map Servers Serving Global-Scale Data A wide range of groups offer interactive mapping of locally-held global-scale data over the Internet. Users should note that in some cases these servers may not deliver the most recent versions of global data available. On the other hand, host organizations may have addressed important data integration issues when pulling together the underlying databases. Users should consult the documentation available from the map server Web sites for detailed information on data sources, versions, corrections, limitations, and overall quality control.

There are a number of places to find standards-based data delivered over the Internet: you can search for map services at WMS Sites or search for GIS data and map services from Mapdex.

Distributed Mapping
An emerging approach to Internet mapping is to access distributed data sources through “map clients” that can query multiple data services using open standards for data interoperability and access. This can provide users with access to the most recent versions of data available from the original or secondary sources. However, users should be aware that assembling disparate data from multiple sources may reveal problems in data integration such as different levels of spatial resolution and accuracy, different geographic referencing and projections, and inconsistencies in coastlines, boundaries, and naming conventions.

Users may choose to use SEDAC’s Internet Map Client, other standards-aware map clients <see spreadsheet> provided by other organizations, or a desktop Geographic Information System (GIS) application <see spreadsheet>.

Downloadable Web Map Contexts SEDAC’s client supports the new Web Map Context (WMC) specification of the Open Geospatial Consortium (OGC). This means that users can store the data layers and geographical extent that have been viewed in the client for future use in the same or a different client. Data providers can also predefine contexts of interest to particular users. See the list below for links to contexts available via the WDC map client.