ArcNews Online

Fall 2006

Successful Centerline Pilot in Maryland with ArcGIS Server

GIS Automates Synchronization of State and County Data

Across the United States, government agencies are increasingly being asked to coordinate efforts with other government organizations. Much of this demand for collaboration is due to new emergency management practices that increasingly require agencies to share data. Since geographic information is an integral part of government processes, police and fire departments, for example, which have traditionally been slow to incorporate GIS into their workflows, are now implementing GIS technology and requesting access to geographic data from neighboring jurisdictions.

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All participants involved in the Maryland Federated Synchronization Project, including the original pilot project participants and the Phase I participants.

In 2001, the Maryland State Highway Administration (SHA) began working with the state's county governments and the City of Baltimore to share street centerline data through the Maryland Cooperative Centerline Program. Centerline data is especially important in Maryland because it is the foundation for much of the state government's GIS applications. The parties in this program share the manually synchronized centerline data, which facilitates information exchanges among the governments and enhances operations.

Each participating government contributes its street-related data and subsequent updates to the Cooperative Centerline Program. The state contributes its linear referencing data, such as route numbers and milepoints, and local governments add detailed information, such as address ranges. The many contributions improve the breadth and accuracy of this shared dataset. Then, each agency can use the rich geodatabase for its unique needs.

At the local level, for example, this data is used to improve emergency response and land-use planning. The state has used the enhanced centerline data to better track roadway assets. At the federal level, the data is fed into the National Map, available through the U.S. Geological Survey.

The Next Generation

Since the Cooperative Centerline Program began, SHA has had to manually synchronize its centerline data with each county's data, which can take up to a year to complete. With many counties involved in this centerline program, SHA can have a substantial number of updates. This labor-intensive process also requires multiple versions of the same dataset to be in use at any given time.

A recent pilot program between SHA and Anne Arundel County—the Maryland Federated Street Centerline Synchronization Project—has demonstrated that, with an agreed-upon schema and the beta version of ArcGIS Server 9.2, the synchronization can happen automatically.

For several months, SHA worked to integrate the Anne Arundel County dataset with its own and to identify an agreed-upon database schema between both entities. SHA is continuing this effort with other counties throughout the state.

With automatic synchronization, it's clear the agencies will save time and increase efficiency. However, there are other advantages to developing this system based on ArcGIS Server, as Mike Sheffer, assistant division chief/GIS coordinator, Maryland SHA, points out. "The benefits also result from developing relationships with people in the county governments, reducing redundancies in data and data collection, and having all the players with a vested interest represented at the table, which creates a more cohesive approach," he says. "It also fosters understanding among the parties since they gain insight into the ways each is using the data and the information that is important to them."

Sheffer continues, "In the future, it will help counties that don't have a GIS in place since SHA can give them this centerline data layer as a foundation for their GIS so that they don't have to develop it from scratch. It will get them into GIS faster and at a lower cost." The benefits of automatic synchronization also reach the citizens since their government will have more accurate data with which to make faster, more informed decisions about situations that impact them.

Model Relationships

Towson University has stepped in to host SHA's centerline data and act as the "parent" replica (the source of the data) in this process. SHA and Anne Arundel County both act as "child" replicas (working off copies of the parent). Through Towson University, the replication is taking place in a connected environment and serves as a critical base layer for Maryland's Spatial Data Infrastructure.

During the initial Cooperative Centerline Program, Anne Arundel County decided to adopt SHA's dataset and data structure. This simplifies Towson University's efforts to synchronize the county and SHA's edits. To edit its data, Anne Arundel County uses ArcGIS Desktop software at the ArcEditor license level. As more counties participate in this automatic synchronization, all parties will have to use a standardized core schema for the data, which is currently being developed.

"This pilot is a perfect example of the way it should be done so that every user has a consistent product," says David Gillum, GIS systems analyst, Office of Information Technology, Anne Arundel County, Maryland. "You know the output of that product is as detailed as it can possibly be since the counties are on the ground actually making the changes and the data is then pushed all the way up to the federal government."

The next phase of the pilot program involves incorporating Baltimore, Frederick, Harford, Howard, and St. Mary's counties into this ArcGIS Server environment and automatic synchronization process. The City of Baltimore and all 23 counties in Maryland are expected to be involved in this program by June 2007.

Once this process moves from a pilot program into production, SHA and each of the counties are expected to synchronize data with the parent replica periodically throughout the year. This should be adequate given the moderate amount of edits the organizations make monthly. The synchronization schedule would be staggered among the counties so that synchronization would be ongoing throughout the year.

Although the synchronization won't take place daily, the automatic synchronization process takes only hours. However, the preparation before and after synchronization can take days since all edits must be complete and quality assurance and quality control checks must be made.

In addition to the benefits the governments in Maryland stand to receive from using an advanced geodatabase synchronization process, one of the most significant aspects to this pilot is the example it sets for other state and county governments. "I think the big success is twofold," notes Sheffer. "We're successfully testing new software and new synchronization strategies, but we're also developing relationships and working on a cooperative agreement. Since counties and states may not have worked so closely in the past, hopefully we will become the model for future endeavors like this."

More Information

For more information, contact David Gillum, GIS systems analyst, Office of Information Technology, Anne Arundel County (e-mail:, or Matthew Felton, director, Center for Geographic Information Sciences, Towson University (e-mail:

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