MCP Insights

Busting a Few Myths Regarding GIS Data and NG911 Readiness

Posted on November 8, 2022 by Robert Horne

Geographic information systems (GIS) have been leveraged to great advantage by public-safety organizations for many years. But in the Next Generation 911 (NG911) environment, emergency callers are located via geospatial routing driven by GIS-generated data, which raises the importance of such systems substantially. In a recent webinar, I explored the relationship between GIS-generated data and NG911 readiness. This blog explores a few of the common myths that have emerged about GIS data.

Myth #1: Procrastinating regarding GIS needs is okay for now — This is completely wrong. Doing so only will delay your organization’s cutover to NG911 service, which represents a quantum leap forward compared with legacy 911 service. It takes an average of 18 months to prepare GIS data to NG911 standards. So, if your organization falls behind on data maintenance, the quality of the data used for geospatial call routing will be compromised. Ideally, every time an address change occurs, a new road is created, or a new subdivision is completed, the GIS database should be updated within 72 hours, at a minimum. Finally, if your GIS professional is not dedicated to the 911 function, i.e., is shared with other county or municipal agencies, your NG911-related needs likely will take a back seat to other projects.

Myth #2: Readying GIS data for use in an NG911 system is a one-and-done effort — This also is completely wrong. Again, every real-world change needs to be reflected in the GIS data as quickly as possible. For example, let’s say that a county or municipality annexes a portion of land possessed by another jurisdiction. That action will change the law-enforcement, fire/rescue, and emergency medical services (EMS) agencies that will be required to respond when a 911 call is made. Every time a boundary changes, it not only has to be reflected in the GIS data, but also needs to be coordinated with neighboring jurisdictions and their emergency-response agencies to avoid gaps and overlaps, which compromise timely and effective response. This is just one of many examples — they key takeaway is that GIS data maintenance is a never-ending effort.

Myth #3: GIS data requirements end at the jurisdictional boundary — Nothing could be further from the truth. Public-safety agencies draw polygons using their GIS that define their jurisdictional footprints and the areas in which they provision emergency services. When such polygons abut, generally along jurisdictional borders, they must “snap” to each other; another way of expressing this is to say that the polygon borders must be coincident. If they are not, overlaps and/or gaps can occur.

If an emergency call is placed in an overlap or gap area between two adjacent jurisdictions, data associated with that call will not be accepted by the NG911 system. When that happens, the system won’t know which ECC should receive the call. The chances are very high then that the answering ECC will not be the correct ECC. And when that happens, the call must be transferred to the correct ECC, a process that usually takes seconds but can take minutes — which is an enormous amount of time when lives are on the line.

Consequently, GIS personnel need to look far beyond jurisdictional boundaries, and coordination with neighboring jurisdictions is critical.

Myth #4: GIS data obtained from free sources can be used in NG911 systems — This generally is a very bad idea. While free data can be used as a starting point by agencies that lack adequate GIS resources, it shouldn’t be used solely to build a database upon which NG911 service relies. The adage, “you get what you pay for,” holds true for free, opensource data, which does not meet basic public-safety requirements, much less established NG911 standards, due to incomplete data attribution, poor spatial accuracy, incomplete coverage of the ECC’s jurisdictional footprint, and inaccurate street names and address ranges, not to mention an unacceptable data-update schedule.

The webinar contains several more myths that are dispelled quite effectively and I urge you to take the time to view it — I am confident that you will find it time well spent. In the meantime, we would love to help you develop a data-development strategy that will help you complete your NG911 migration more easily and quickly — please reach out.

Robert Horne is MCP’s technical domain lead. Email him at

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