March 11Transportation for the NationCase Study – Virginia:Northern Virginia Regional Routable Centerline ProjectTFTN Strategic Plan Case Study
Overview:The Data Collection and Analysis project consisted of five jurisdictions inthe Northern Virginia area, which are all Public Safety Answering Points(PSAP), as well as the Virginia Information Technology Agency (VITA) andthe Virginia Department of Transportation (VDOT), in active collaborationto develop a routable centerline data set and standard usable bycomputer-aided dispatch (CAD) systems. The updated standard will beapplied to the Virginia Geographic Information Network (VGIN) stateroad centerline file format (RCL) and be employed in future projects.The participating jurisdictions are Fairfax County as the project lead,Arlington County, Alexandria City, Loudoun County, and Prince WilliamCounty. The interior jurisdictions to these larger areas, such as Fairfax City,Falls Church City, Town of Herndon, etc., will be included in the projectwherever possible. This business process is in place—see Figure below—and is used effectively to get basic street centerline information for anyother jurisdiction. It is expected that this project will improve on the existingbusiness process and the data supplied. The project has been funded bythe 911 Fund, which helps pay for the PSAP Grant, and various other stateprojects including the state orthophotography road centerline project.
The purpose of this project is to enhance VGIN RCL to create a regionalstreet centerline capable of supporting routing, geocoding, and persistentupdates to local 911 map systems. It will allow for design, development,updating, and population of an enhanced RCL which will fully supporteach individual CAD system for data outside their own jurisdiction, whilenot forcing them to change the data model currently used in CAD. FairfaxCounty recently went live with a new CAD system with AVL, and hasgained a full understanding of what is needed in GIS to support routing. Ina perfect world, Fairfax County would be square and all routing could beconducted within its own jurisdiction. Then, there would be no need toroute outside of its borders. However, since that is not the case, thecounty is dependent upon data outside of its borders.Project Background:The goal of this effort is to generate and use a persistent set of unique IDsthat will provide a way to track and identify changes at the centerlinelevel. As part of the maintenance process, VGIN collects and distributesdata from local jurisdictions based on a FIPS code—jurisdictiondesignation—for each arc in the data set.For the current use of VGIN data, it makes no difference which jurisdictionan arc straddling two jurisdictions originates from. However, once thoselocal governments try to use these data in a CAD system, it makes anenormous difference. Consider the example of Rynex Rd. on the border ofFairfax County and Alexandria City. A portion of this street has Fairfaxaddresses on both sides; a portion has Fairfax addresses on one side andAlexandria addresses on the other. Both jurisdictions need arepresentation as part of their database to support a CAD system. Usingthe current process, only one would be imported into the VGIN data,causing problems with future updates. This project will develop atechnical solution to this problem, as well as a methodology and bestpractices guide that other jurisdictions can use to resolve the same issue.For data outside of Fairfax, the team used the State RCL data. The processof incorporating this data was not intended for a single use due to issueswith this data and the amount of work required making it work withexisting CAD systems.Lessons Learned and Challenges:The data needed to be edge-matched which means that the State datastreets didn’t match up with the data where it should have, so each street
along the borders needed to be realigned to match so that there isconnectivity.Throughout the process, there were additional issues with the way dualroadways were represented—Fairfax maintains dual centerlines whereothers maintain a single centerline, so those needed to be matched up atthe borders.There were also inconsistent naming standards, which posed a problemwhen considering the round trip of the data. One-way information wasabsent from the dataset and because of this, at one point during testing,the team was able to identify a route that went the wrong way up aramp. Speed limits were missing on the state data, and proper routingwithout speed limits is not possible. There were overlapping addressesand/or gaps at the borders, which could result in two possibilities for oneaddress, and some addresses not being recorded. These issues, inaddition to the Fairfax experience, are all justification for a regionalroutable centerline.
Conclusions:The VGIN RCL project is considered a huge local success because of thecommunication and handshaking that occurs between the state and thestate DOT. This is an ongoing project that will eventually have a seamlessflow from participating cities and counties up to the state and then backagain to complete the round trip. Additional work on the project includesthe development of maintenance tools and the integration of regionaldata into CAD systems.Sources: Brendon Ford (GIS Applications & Systems Administrator FairfaxCounty Department of Information Technology), Brian Wooley (StreetCenterline Coordinator, Loudon County), Mike Fauss (Manager of theLand Records Maintenance Division, Loudon County), Dan Widner(Coordinator, Virginia Geographic Information Network, VirginiaInformation Technologies Agency (VITA)), Larry Stipek (Director of theOffice and Mapping and Geographic Information, Loudon County)