NG9-1-1: GIS Data Accuracy and Currency

David Hamilton

The 9-1-1 system is all about routing a call to the most appropriate 9-1-1 Public Safety Answering Point (PSAP). As we mentioned in the past blog posts, NG9-1-1 will migrate from using pre-built tables that depend on hard-coded links between civic address location and PSAPs to using actual call coordinates to find the appropriate 9-1-1 PSAP servicing a location. In this blog post, Holly Barkwell, Canadian Region Director of the National Emergency Number Association (NENA), explains the importance of data accuracy and currency in NG9-1-1.

The current pre-processing model has the luxury of long lead times to resolve issues with GIS data, whereas NG9-1-1 will access GIS systems and services at the time of the call. Data issues not caught and resolved prior to a 9-1-1 call will impact the ability to efficiently route the call to the appropriate 9-1-1 PSAP and for the PSAP operator to successfully process the call. It isn’t hard to imagine the consequences of response delays if GIS data isn’t accurate or up to date.

In the previous blog post, NG9-1-1: Why we need data to be Complete, we explained why GIS data needs to be complete. In this post, we explain NG9-1-1 GIS data accuracy and currency goals. Accuracy includes position and attributes that describe the feature.

The following is an excerpt from the NENA GIS specification section 2.7 on positional accuracy:

“The horizontal accuracy of the GIS data layers SHOULD meet the National Spatial Data Infrastructure’s (NSDI) “National Standard for Spatial Data Accuracy” [7] at a scale of 1:5000. This equates to a horizontal accuracy of +/‑ 13.89 feet at 95% confidence.”

To meet the above standard, organizations may need to upgrade their point feature locations. It may also mean adding intermediate points to linear features such as road segments and boundaries.

Street address attributes in GIS data are vital to correct routing of 9-1-1 calls to the appropriate PSAP. Landline calls will continue to use this data to determine call location and 9-1-1 routing, while new generation mobile devices can already provide call location coordinates. In both cases, location will be used to determine call routing to the appropriate PSAP. The location of a mobile call will also use the GIS data to determine the nearest street/address.

Accurate street attributes (address ranges and names) and precise alignment of public safety boundary data are very important for not only properly routing 9-1-1 calls, but for the PSAP operator to confirm the emergency location. A 9-1-1 call taker and dispatcher (if they are different) MUST have confidence in both the geometry and attributes of the GIS data to confirm call location; and, responders must have confidence that they have arrived at the correct location.

Accuracy won’t matter if the GIS data in the 9-1-1 system is not current. Standards/goals for currency are currently being developed by the CRTC Emergency Services Working Group (ESWG). The goal is to have updates (for example, new road segments) applied to the system within days of being confirmed. We will talk about currency specification/goal in a future post.

NG9-1-1 will revolutionize how location information is accessed and processed within the 9-1-1 system. That said, to make efficient use of the information, back-office technology and processes must change. NG9-1-1 functions will require GIS data to be accurate and up to date. Providers of this GIS data to 9-1-1 and public safety must be aware of and adapt to new pressures that NG9-1-1 brings.

When the national data model for NG9-1-1 gets approved, we will author another post to explain it. Stay tuned!