ArcWatch: Your e-Magazine for GIS News, Views, and Insights

March 2010

Structure: The Key to Volunteered Geographic Information

New Tools Enable the Public to Participate in GIS Database Development

By Matt Artz, GIS and Science Marketing Manager

For many years, Esri has promoted the idea "GIS is for everyone." More recently, the pace of this movement has accelerated, thanks to the Internet. We tend to think of GIS for everyone as a broad, practically universal access to data and GIS/mapping tools. But another facet is the public's involvement in that fundamental, essential component of GIS-building and maintaining the geospatial database.

Traditionally, geospatial databases are owned by the creators of the geographic information. These are typically individuals or groups charged with building and maintaining the databases that support their organization's missions. These databases are considered "authoritative," meaning that they meet the standards of the organizational creators and will suit the needs of their intended applications. But this database workflow has its critics.

"One of the criticisms leveled at GIS has been its insistence on a single point of view," said Michael Goodchild, professor of geography at University of California, Santa Barbara. To address such criticism, Goodchild said that a framework is needed "in which individuals are able to assert their own views of their surroundings and play a part in local decision making."

In the GIS realm, volunteered geographic information (VGI) is geographic information that end users or the general public create. VGI is assertive geospatial data. While the data provider may be confident in its accuracy, this does not necessarily guarantee the data meets the organization's information standards or that it is suitable for the intended application.

Concerns about VGI are many. In contrast to GIS-based data, which is organized with consistent data models and collected systematically, VGI is mostly observational and qualitative, and very rarely is it collected systematically in a science-based framework. Typically, it is not collected in a structured framework, nor is it associated with metadata, and there is little or no formal responsibility for data quality.

So is VGI valuable in a GIS environment? Yes. There are many ways GIS users can take advantage of the rapidly growing amount of VGI on the Web, including

This method of collecting observational geographic data and getting the public involved is powerful, especially in getting people in the community to collaborate and communicate about situational awareness.

"I think the most significant new opportunity lies in the fact that a substantial fraction of the human population now has access to mobile phones and, hence, to electronic networks," said Goodchild. "Mobile phones could be used to acquire and share damage assessments in the immediate aftermath of a disaster and to develop detailed databases for community planning."

Structure Is Key

The key to useful, actionable VGI is to collect the data in a structured manner. The United States Geological Survey-Caltech Recent Earthquakes application ( is an interesting example of how to do this. Recent Earthquakes lets people report via the Web what they experienced during an earthquake, but it doesn't ask them to rate the intensity of the earthquake directly. Instead, it walks people through a more objective, structured series of questions to help determine how strongly they felt the earthquake.

On the back end, the application determines the intensity of what people felt during the temblor as an aggregate of responses to individual questions. The Web-based map is an interesting and useful service in itself, but potentially even more useful is that the answers to the individual questions also form a valuable dataset for further analysis.

Esri has been building functionality, such as the new featurelayer capabilities in ArcGIS 10, to support such structuring of VGI. Web APIs for capturing information are being developed; structured volunteered geographic information becomes another geographic layer in the geodatabase; and advanced applications, such as analysis, modeling, forecasting, management, and planning, are enabled by structured data. Esri will continue to develop technology that builds these concepts into ArcGIS and make it an integral part of the GIS architecture.

Times are already changing.

"There are already signs that the traditional authorities are willing to work with citizens," said Goodchild. "In the UK [United Kingdom], for example, the Ordnance Survey has developed a program that encourages volunteers to provide geographic information about their local communities. Volunteers are playing an increasingly important role in ensuring that authoritative sources of geographic information are accurate and kept up-to-date."

Power of the People

Consuming VGI in a GIS environment gives the public unprecedented power.

"Our military has a slogan: Every soldier is a sensor," said Esri president Jack Dangermond. With VGI, "every citizen is a sensor. This is another chapter in democracy, opening up and letting citizens participate in the development of geographic databases."

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