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NG9-1-1 Address Points and Boundaries: More than Just Points and Polygons

December 15, 2020

This month, we continue our discussion about the role GIS plays in Next Generation 9-1-1 (NG9-1-1). In our October article, we talked about how the NG9-1-1 Location Validation Function (LVF) and Emergency Call Routing Function (ECRF) fundamentally change how 9-1-1 calls are located and routed using GIS data. With GIS at the heart of NG9-1-1, we identified the importance of establishing a roadmap to creating and managing public safety GIS data that follows the NENA Standard for NG9-1-1 GIS Data Model (NENA-STA-006.1.1-2020).

The NG9-1-1 GIS Data Model defines five GIS data layers that are critical to the successful deployment of the LVF and ECRF. Our previous article discussed the importance of maintaining accurate and reliable Road Centerline data. This article looks at the next four layers required by the NG9-1-1 GIS Data Model, outlines a roadmap for GIS data readiness, and demonstrates why it’s critical to spatially validate NG9-1-1 GIS data.

Required data layers

Site/Structure Address Points

Site/Structure Address Points (SSAP) identify the locations of structures, sites, landmarks, and their access points. Address points give us the ability to locate sites that may not otherwise geocode correctly via road centerline data, and areas with odd addressing. Address points offer the most precise call and resource routing, including to non-addressed dispatchable locations. Understanding the advantages and disadvantages of the various methods to place address points and geocode SSAP locations enable GIS and 9-1-1 authorities to create accurate, reliable, and consistent data used for 9-1-1 and NG9-1-1 applications.

NENA provides a wealth of information, guidance, and recommendations for creating and managing the Site/Structure Address Points data. The NG9-1-1 GIS Data Model clearly lays out the standards for this data, and the NENA Information Document for Development of Site/Structure Address Point GIS Data for 9-1-1 provides an effective guide to developing and managing SSAP data for use in existing 9-1-1 applications and NG9-1-1. NENA’s recommendations for creating and managing SSAP data fully support NG9-1-1, improving the quality of your existing data while preparing you for NG9-1-1.

PSAP Boundaries, Emergency Service Boundaries, and Provisioning Boundaries

The NG9-1-1 GIS Data Model also defines the boundary layers required to successfully implement NG9-1-1. Effective development and management of each required boundary layer requires communication with neighboring jurisdictions, adherence to NENA recommendations and standards, and implementation of a GIS data management solution designed to support NG9-1-1 which provides spatial validation of the 9-1-1 Authority’s GIS data.

The PSAP Boundary depicts the information used to define the geographic area covered by the 9-1-1 Authority. This boundary layer is used to route 9-1-1 calls and emergency services requests delivered through the NG9-1-1 system. Establishing accurate PSAP Boundary data requires coordination with neighboring jurisdictions to ensure there are no gaps, overlaps, or duplication of polygons.

Emergency Service Boundary (ESB) layers define the geographic area for individual emergency response providers such as law enforcement agencies, fire departments, emergency medical services authorities, and others. ESB layers enable PSAPs to identify the appropriate first responders or emergency responders within their geographic area. Separate ESB layers are required for each type of service and may contain one or more polygon boundaries defining the primary emergency services for the given area.

The Provisioning Boundary defines the 9-1-1 Authority’s area of GIS data provisioning responsibility. Boundary information must be agreed to by all adjoining provisioning providers, and cannot contain unintentional gaps or overlaps. This effectively becomes a geofence for the 9-1-1 Authority for data submitted through the Spatial Interface.

NG9-1-1 GIS Data Readiness and Your Data Management Roadmap

Every state, county, or jurisdiction deploying Next Generation Core Services and turning up an NG9-1-1 ESInet will benefit from setting a clear vision for preparing data for NG9-1-1. This requires an understanding of the realities of NG9-1-1 readiness, which extend far beyond a 98% match rate of ALI and MSAG to GIS, and purposeful work to establish the workflows and processes that improve GIS for current 9-1-1 operations and truly prepare it for NG9-1-1.

DATAMARK’s Process

Effectively Validating Your NG9-1-1 Address Point and Boundary Data

With spatial data forming the foundation of every NG9-1-1 environment, 9-1-1 authorities will become responsible for performing quality checks (QA/QC) and resolving issues in the GIS data before it’s provisioned into the Spatial Interface. These issues potentially include invalid geometry, gaps and overlaps in boundary data, duplicated attributes, missing fields and mismatched data types, and address range issues along the road centerline.

A number of these issues are revealed through spatial validation more effectively than through tabular validation of the data, defining a critical need to deploy a validation engine that performs comprehensive and meaningful spatial validations on your data. Failing to consider and perform spatial validations can result in overlooking data issues which potentially delay implementation of NG9-1-1 or prevent you from achieving NG9-1-1 GIS readiness. Tabular validations are still critical to preparing and maintaining data for NG9-1-1, but spatial validations quickly identify issues that could be easily missed without them.

Topology Checks enable us to easily identify overshoot and undershoot errors.

Overshoot and undershoot

Fishbone Validation of address data against the road centerline identifies potential address point placement issues which may not be caught in tabular validations.


Spatial validation of boundary polygons effectively identifies gaps and overlaps between neighboring PSAPs which could negatively impact call location and routing.

Gaps and Overlaps

The Circle of NG9-1-1 GIS Data Maintenance

The work required to maintain GIS data for NG9-1-1, meeting or exceeding NENA standards is never complete. As we’ve shown, GIS becomes central to all things NG9-1-1, and jurisdictions deploying Next Generation Core Services will need to integrate GIS data maintenance and remediation into their ongoing operational processes.

The NG9-1-1 LVF and ECRF require accurate and reliable GIS data which is always up to date. Maintaining NG9-1-1 GIS data is a cyclical process of validation, markup, review, and provisioning driven by well-defined workflows performed with an advanced validation engine purpose-built to support NG9-1-1.

VEP Process

DATAMARK: A Trusted Partner for NG9-1-1 GIS

As with Road Centerlines, NG9-1-1 GIS data readiness and effective management of NENA’s required Site/Structure Address Points and Boundary layers also requires a complete understanding of the NG9-1-1 GIS Data Model. Developing GIS data that follows the standards for NG9-1-1 benefits 9-1-1 Authorities in the near term by cleaning up data used in existing 9-1-1 applications and prepares for NG9-1-1 implementation.

As we continue exploring the challenges and opportunities presented by the transformation of your GIS environment to support NG9-1-1, we hope you are better prepared to ask and answer the following questions:

  • Does my GIS data support the caller’s location completely, accurately, and precisely?
  • Does my GIS data support accurate queries for the proper routing of the 9-1-1 call?
    • Topology: Is my geographic representation correct?
    • Attribution: Have I addressed all mandatory and conditional requirements?

If you continue to struggle with any of these questions, please reach out to us. DATAMARK’s team of public safety GIS professionals is ready to help, and our comprehensive suite of GIS data management solutions will equip you to meet your existing GIS needs and prepare you for the bright future NG9-1-1 offers.