Spatial data plays a critical role at every step in this process. Knowing the location from which an emergency call is made is crucial in knowing how to respond to an E911 call. An effective GIS-based E911 system allows public safety personnel to plan for emergency response, determine mitigation priorities, analyze historical events, and predict future events.
Not all data is created equal however. E911 service providers and PSAPs need to be conscious of the varying quality of both private and commercial spatial data. My own company, Geographic Data Technology, provides street data products that have proven to be useful throughout the E911 process.
The FCC's order, titled FCC 94-102, requires a technology-based solution to enable PSAPs to locate wireless 911 callers by way of a desktop map. By having a highly accurate, detailed street map database available, PSAPs will be able to effectively manage and route a wireless call to the proper ESZ. This creates the need for accurate spatial data and a variety of mapping functionality.
E911 service providers typically handle calls from locations across the United States, so it is critically important for them to use spatial data that includes the complete national inventory of streets. A comprehensive transportation network, extending seamlessly from central cities to rural areas, is the starting point for these E911 applications.
Feature Completeness and Accuracy
While a cursory comparison of two data sets may reveal more streets in one than the other, raw numbers are not the only issue. As discussed below, a complement of features (including, at minimum, addresses and political boundaries) is also required for accurate location of callers. Unfortunately, differences in these features are not so readily apparent. To gauge the completeness and accuracy of a data set, these questions must be answered:
Many commercial spatial databases were derived from TIGER files developed by the U.S. Bureau of the Census. Such data will often meets National Map Accuracy Standards (NMAS) for 1:100,000 maps, providing horizontal accuracy of +/-167 feet. For modern spatial data applications, this represents the minimum standard of accuracy.
Positional or Geometric Accuracy
Some spatial data vendors have embarked upon programs to improve their geometric accuracy by repositioning and reshaping the street and feature network to reflect superior "groundtruth". GDT, for example, uses satellite imagery, aerial photography and GIS vector databases evaluated for their positional accuracy and data currency. GDT has found that, at a minimum, any raster or vector source will conform to NMAS for 1:24,000 map, yielding positional accuracy of +/- 40 feet. However, field validation using GPS technology has consistently shown that GDT is able to obtain accuracy results in the +/- 20-25 foot range (consistent with the NMAS for 1:15,000 scale maps) when utilizing one-meter resolution Digital Orthophoto Quad imagery (DOQs).
Positional accuracy is very important for wireless E911 applications, but customers should not automatically make the assumption that the dataset with the highest degree of accuracy is the mandatory choice. The FCC Phase II mandate requires that an emergency agency be able to locate a person making a wireless E911 call to within 100 feet of the phone's location. Positional accuracy is important, in many instances, however, relative accuracy is more critical.
At the most elementary level, attribute completeness involves having every street on the map and having a name and address range on every street segment. But in addition to maintaining and updating this information, it is important that street names are standardized and that these standards are reflected in the data, that feature classifications (such as road type, traffic controls, etc.) are consistent and current, that routing and impedance information is consistently applied, and that roadways have a consistent and high degree of connectivity. To understand how data providers meet these requirements, these questions must be addressed:
Often the best sources of information on a community's streets are the people who live there and drive those streets on a daily basis. It is important for spatial data providers to actively collect and integrate this local knowledge through a formal process, in which customer feedback is incorporated into the core database and becomes available in a timely manner. Similarly, it is important for spatial data providers to maintain relationships with government agencies and private map producers to make sure that they have the most current resources for reference.
Data Set Currency
The U.S. Postal Service is another excellent source of data improvement, providing monthly updates on postal changes occurring throughout the nation. The USPS makes between 50,000 and 100,000 changes each month, adding new ZIP Codes, splitting current ZIP Codes, adding new addresses and making other changes to the nation's 23 million postal street addresses. When the USPS makes those changes in ZIP Code distribution, it effectively changes the entire address for every residence and business within the changed area. Customers of spatial data should be aware of how prospective data vendors incorporate USPS data and on what schedule.
Priorities for updating spatial data in a specific area should be determined by a number of factors including a county's growth rate, the institution of a local E911 re-addressing program that drastically alters the "locational landscape", the availability of feedback from daily users within that area and the availability of reliable addressing resources from governments, map publishers and others resource. But no matter how frequently a data provider updates a given area, there are times when a customer will need more focused updating. It is important that spatial data providers have both the resources and procedures to offer custom updating programs to meet specific customer needs in a cost-effective and timely manner.
TeleCommunication Systems (TCS), formerly known as Xypoint Corp., is an advanced network services company created specifically to bring low-cost, user-friendly location-enhanced services to mobile people. Using Esri's ArcSDE™ (Spatial Database Engine™) software and GDT's nationwide Dynamap/2000® street data, TCS has created a location-based E911 emergency response system. The system uses signals from cell sites to quickly match a caller's location to the closest address or landmark for emergency dispatch.
TeleCommunication Systems (TCS)
As a E911 calls travels to the emergency dispatcher, TCS's system uses a separate server in its 24-hour Network Operations Center (NOC) to process the caller's 10-digit cellular phone number, determine its general location and forward the information to the PSAP. The voice and data arrive simultaneously. On a single screen, the PSAP emergency dispatcher sees the 10-digit phone number, a geographic description of the caller's location based on the nearest cell tower and numbers for the closest emergency response agencies (such as police, fire or EMS).
Since wireless callers nationwide make 50,000 to 100,000 E911 calls each day, the system is expected to speed response and improves subscriber safety. With current technologies, it is impossible for emergency dispatchers to trace dropped calls or locate callers who don't know where they are or can't speak to them. Now the wireless phone, rather than the customer, can supply location data and signal emergency services that help is needed.
Key components at the heart of the TCS system are Esri's ArcSDE technology and GDT's Dynamap/2000 street network, which enable millions of spatial features to be stored and managed in a commercial database. The quality and accuracy of GDT's data helps providers to meet Phase II requirements of locating the caller's location more precisely, within 125 meters (about half a block). The E911 system also searches an Oracle® database of 5500 PSAPs built from GDT's nationwide Dynamap/2000 street database. For more information on TCS, go to www.telecomsys.com.
Intrado, formed with the acquisition of Lucent Public Safety Systems by SCC Communications Corp., is a leading provider of innovative solutions for complex data management, notification services and networked transactions to the telecommunications industry. Named Esri Partner of the Year for 2000, Intrado is to a strong proponent of Esri products and services and has been proactive in the implementation and refinement of the ArcIMSTM SDK and ArcSDE software. The geospatial component of Intrado's product offerings is based on GDT's Dynamap/2000 database and Matchmaker® SDK Professional geocoding product.
Intrado is creating innovative products and services for E911 and Early Warning and Evacuation (EWE) programs that take advantage of Esri technologies and GDT's nationwide spatial data. Incumbent Local Exchange Carriers (ILECs), Competitive Local Exchange Carriers (CLECs), Integrated Communications Providers (ICPs), and wireless carriers can outsource their 911 management requirements to Intrado, saving them time and money and allowing them to focus on their core business.
Intrado's 9-1-1ConnectSM is a simple, cost-effective solution that complies with both Phase I and Phase II of the FCC mandates. For wireless carriers that have not yet achieved Phase II compliance, 9-1-1Connect provides an easy migration path to Phase II service levels. For its first live-call trials of Phase II capability, Intrado chose the heavily traveled New Jersey Turnpike, supporting live calls for 90 days. The system provided caller locations within the mandated 125 meters and mapped the best route to the caller based on the x-y coordinates provided. Additionally, 9-1-1Connect provides the capability for a wireless subscriber information service, allowing subscribers to store their name, address and phone number in Intrado's national Automatic Location Information (ALI) database. This information can then be transmitted to the appropriate PSAP when a wireless call is made by the subscriber.
As wireless subscribers move and addresses change, data in a carrier's Master Street Address Guide (MSAG) must be updated in a timely, efficient manner. Intrado developed 9-1-1Net® as a user-friendly electronic tool that gives PSAPs more control over their MSAG. This Internet-based application allows users to view "live" MSAG information, access status and reports and submit misrouting information, ANI-ALIs and MSAG Ledgers electronically, on-line in real time. Additionally, the system provides a detailed audit trail and several other convenient services.
GDT is proud that Intrado relies on its data to meet these leading-edge GIS initiatives. For more information on Intrado, go to www.intrado.com.
Without question, the easiest way to update large amounts of spatial data is to depend upon the original data supplier for scheduled updates. This plan, however, presents a double-edged sword. While freeing users from having to gather and manage thousands of changes and incorporate them into a data set, it also separates users who are the closest to their communities from the hands-on process of keeping the data up to date.
In an effort to keep life simple for users while still empowering them to make changes quickly, data suppliers frequently offer user feedback loops. The traditional loops are request-based: users send written information about changes in local geography, and the data supplier makes the edits. There can be a considerable time lag in this process.
A new development for feedback loops is the Community UpdateTM program, created by GDT in partnership with Esri. Through a data-sharing agreement, local and regional governmental agencies use an Internet-based system to send new and updated information about local streets to GDT where it is validated, cross-referenced and integrated with other data, then returned to a central server for downloading by those agencies. The program will reduce the time required to update street data and deliver more accurate information to GDT data users and their constituencies.
In addition to simplifying the process of adding new streets and features, the Community Update program can be an excellent tool with which PSAPs may manage their ESZ boundaries. Through Community Update, PSAPs have easy access to GDT's base map data that provides the foundation and the building blocks to create, update and maintain these boundaries.
For more detailed information on the Community Update program, see "Community Update Brings Faster, More Accurate Updating of Data" (ArcNews, Fall 2000) and "Current Spatial Data for Communities" (Government Matters, Winter 2000). Or go to www.communityupdate.com.
Obvious applications include routing and navigation of emergency vehicles to where they are needed. Broader applications for PSAPs including emergency response planning, development of mitigation priorities, historical event analysis and future event anticipation. The following examples of public safety-related applications is derived from Bill Weaver's article "What GIS Advancements Mean to Public Safety," mentioned above:
Beyond the PSAP office, governments may use spatial data for scores of purposes, including transportation planning, taxation, facility inventories, police incident reporting, and many other applications previously discussed in Esri publications… and many yet to be developed.
ArcSDE, Spatial Database Engine and ArcIMS are trademarks of Esri. Dynamap/2000 and Matchmaker are registered trademarks and Community Update is a trademark of GDT. Oracle is a registered trademark of Oracle Corp. 9-1-1Net is a registered trademark and 9-1-1Connect is a service mark of Intrado.