Uncovering Hidden NG9-1-1 GIS Data Problems with DATAMARK VEP

April 22, 2019

GIS Professionals spend years collecting and curating high-quality data, including site/structure location data using GPS or road centerlines from satellite imagery. Some have even provisioned all or parts of this data to the local Public Safety Answering Point (PSAP) to help them locate the source of 9-1-1 calls.

During a 9-1-1 call, every second counts if someone’s life is often on the line. Getting an emergency responder to the scene is life-critical. If your GIS data can’t lead first responders to a scene, lives – even agency reputations – are at risk.

DATAMARK VEP is a software-as-a-Service (SaaS) application that allows users to easily validate, edit and provision data for use in Next Generation 9-1-1 (NG9-1-1) or other schemas by simply uploading data (which initiates a validation) then reviewing the results in a map or dashboard. The powerful validation engine helps catch potential problems, such as the ones discussed below, in the GIS data before they plague a 9-1-1 call.

A Close Call

A colleague of mine relates a story in which a 9-1-1 call was routed to her PSAP. A desperate mother called seeking help for her son, who had just overdosed. The dispatcher quickly determined the mother’s location and sent an ambulance to the address, a condominium on 323 East Main St.

Help got to East Main Street quickly. However, the paramedics quickly realized that all the addresses on this street were evenly numbered. There was no unit 323.

Frantically, the paramedics called the dispatcher. The dispatcher checked her map and it clearly indicated an address between 322 and 324. Just when it seemed that tragedy would strike this family, a curious neighbor approached the ambulance and asked what was going on.

Thankfully this neighbor directed the paramedics to unit 323 which was behind the even-numbered units and faced another street, 3rd Ave. The paramedics rushed over to 3rd, entered the unit, administered an antagonist and saved the young man’s life.

Detect Data Problems

It is not uncommon for communities to have odd and even numbered addresses on the same side of the street. These communities often experience organic, dramatic growth and do not follow good addressing practices until after such growth has occurred. As seen in countless anecdotes, this can lead to unintended, and in some cases life-threatening, consequences.

DATAMARK VEP was built to detect this and many other conditions. In this case, the software flags these addresses as an anomaly to the Address Point is on Wrong Side of the Road Centerline rule. This validation verifies that address points fall on the side of the road indicated in the road centerline’s address range parity attribute.

With field verification, these addresses are marked as exceptions and managed in the GIS data through alias tables or attributions to indicate that access is on another street.

Address Point – Duplicate Point
DATAMARK VEP includes Address Point – Duplicate Point validations and flags these conditions, helping resolve and correctly attribute them. In a recent data readiness check (a free validation service we provide for municipalities, counties, PSAPs and other entities), more than 7 percent of all features validated were flagged as duplicate points.

NG9-1-1 uses a point-in-polygon operation to automatically route a 9-1-1 call to the closet available PSAP. If there are duplicate address points in the system, the call may not be routed to the correct PSAP or the responders may be sent to the wrong location.

In NG9-1-1, each address point must represent a unique location point. This might seem obvious, but addresses are tricky. NG9-1-1 requires the use of additional fields to uniquely identify an address that shares a common primary address with other points.

Address Point not reflected in Road Centerline
Many GIS careers begin as an intern fixing topology errors, such as overshoots, dangling nodes and slivers. GIS tends to focus on topological and spatial errors while accepting, ignoring or inheriting attribute value problems.

Frequently hand entered, abbreviated and not verified, addresses are some of the most inconsistent and dirty attribute data. Address points can have incorrectly spelled street names or inconsistent street types. They may even reference streets that do not exist in the road centerline data.

Whatever the cause, this leads to problems in a 9-1-1 system that uses that data to route calls.

DATAMARK VEP checks for this condition using the Address Point not reflected in Road Centerline validation and helps users easily correct flagged points within the application. In the data readiness check mentioned above, nearly four percent of all address points had this anomaly. Four percent may seem low but consider four percent of 84,500 (the number of centerline features in Los Angeles) is 3380. That is a very large number of potential 9-1-1 call routing problems.

MSAG Has No Matching Road Centerline
When an incoming call is placed using a wireline phone instead of a mobile device, 9-1-1 uses a Master Street Address Guide (MSAG) to locate the caller. An MSAG is a tabular, non-spatial dataset that holds information such as street names, street ranges and address parity values.

Depending on where you live, 15-20 percent of all 9-1-1 calls are from wirelines and therefore use an MSAG. As an example, PSAPs in Los Angeles County took over 1.2 million wireline calls in 2017.

NG9-1-1 replaces the MSAG with GIS datasets like road centerlines and address points. Therefore, the GIS data must answer the same questions as the MSAG. Consider the Los Angeles example above. When NG9-1-1 begins using GIS data to route those 1.2 million calls, the data in the MSAG must also be in the road centerlines.

DATAMARK VEP verifies that unique street names listed in the MSAG also appear in the road centerlines, helping you prepare for the transfer from MSAG to GIS for NG9-1-1 rollouts. If the data doesn’t correlate, DATAMARK VEP flags anomalies as MSAG Has No Matching Road Centerline

How common is this condition? Again, referencing the free data readiness check mentioned earlier, forty-two percent of street names listed in the MSAG were flagged as anomalies. This is a frequently occurring, yet easily resolvable condition. Contact DATAMARK for a free data readiness check so you can ensure accuracy in your life-critical GIS data for NG9-1-1.

By: Stephanie McCowat

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