NG9-1-1 Glossary

NG9-1-1 Acronym & Terminology Guide

A  |  C  |  D  |  E  |  F  |  G  |  K  |  L  |  M  |  N  |  P  |  Q  |  R  |  S  |  T  |  U  |  V  |  W  |  Z

• Address candidate: A location identified as likely missing from, or inconsistent across, a jurisdiction’s address data. Usually identified through Address Comparison Evaluation (ACE). Candidates are unvalidated until the jurisdiction reviews them and decides whether to adopt each one. 
• Address data governance: The ongoing work of keeping an address record consistent across the government systems that depend on it, including GIS, CAD, the Master Street Address Guide, tax and assessment records, permitting, and utility billing.  
• Address range: The low and high house numbers assigned to each side of a road segment. Legacy 9-1-1 validates addresses against ranges; NG9-1-1 relies increasingly on individual address points. 
• Addressing authority: The agency legally responsible for assigning addresses in a jurisdiction, often a planning or building department and not the 9-1-1 authority. The handoff between the two is a common source of address gaps. 
• ALI: Automatic Location Identification. The database queried during a 9-1-1 call that returns the caller’s address and callback number to the telecommunicator. 
• ANI: Automatic Number Identification. The 10-digit telephone number associated with a device used to call 9-1-1.
• AVL: Automatic Vehicle Location. A means of determining a vehicle’s geographic location and transmitting it to a point where it can be used. 
• CAD: Computer-Aided Dispatch. The system dispatchers work in to receive a call, locate the incident, and assign responding units. 
• Civic location: A location described by address elements such as house number, street name, unit, and community. NG9-1-1 validates civic locations against GIS data through the LVF.
• Data aggregation: Combining GIS data from multiple local sources into a single regional or statewide dataset, as NG9-1-1 requires. Aggregation surfaces conflicts at jurisdictional edges. 
• Data steward: The person or agency responsible for the accuracy and maintenance of a GIS dataset. NENA uses the term for the local authority that maintains 9-1-1 GIS data. 
• Discrepancy agency: The agency named in each NG9-1-1 GIS record as the recipient of error reports about that record. The NENA NG9-1-1 GIS Data Model requires the field on every feature.
• Dispatchable location: The civic address of a 9-1-1 caller plus any detail needed to find them, such as suite, floor, or room number. FCC rules implementing RAY BAUM’S Act require it for multi-line telephone systems and many calling services. 
• E9-1-1: Enhanced 9-1-1. The legacy system that delivers a caller’s number and location (ANI and ALI) to the answering point, using tabular MSAG and ALI databases. NG9-1-1 replaces it. 
• ECRF: Emergency Call Routing Function. The functional element in an ESInet that routes 9-1-1 calls toward the appropriate PSAP using spatial operations on GIS data. 
• ESB: Emergency Service Boundary. The geographic area for which an emergency service agency holds dispatch responsibility. 
• ESInet: Emergency Services IP Network. The managed network that carries 9-1-1 calls and data in an NG9-1-1 environment, replacing the dedicated circuits legacy 9-1-1 depends on. 
• ESN: Emergency Service Number. A 3- to 5-digit number assigned to each MSAG record that represents an ESZ and identifies which agencies to dispatch. 
• ESRP: Emergency Services Routing Proxy. An ESInet component that selects the next hop for a call based on location and policy. 
• ESZ: Emergency Service Zone. A geographic area representing a unique combination of emergency service agencies within a 9-1-1 authority’s jurisdiction. 
• ETL: Extract, Transform, Load. The process of pulling data from a source system, converting it to a target schema such as the NENA data model, and loading it into the destination. 
• FGDC Address Standard: The United States Thoroughfare, Landmark, and Postal Address Data Standard (FGDC-STD-016-2011), the federal standard for recording and exchanging address data. 
• Gap analysis: An assessment comparing current data against a required standard or other authoritative sources to identify what is missing or inconsistent. 
• Geocoding: The process of converting a text address into map coordinates. A failed or approximate geocode is often the first visible sign of a missing or inconsistent address. 
• Geodetic location: A location expressed as coordinates, such as latitude and longitude, usually with an uncertainty radius. Wireless 9-1-1 calls typically deliver geodetic location.
• GIS: Geographic Information System. The mapping system a jurisdiction uses to maintain address points, road centerlines, and boundaries. Under NG9-1-1, it becomes the authoritative source for locating a caller. 
• Kari’s Law: Federal law (2018) requiring multi-line telephone systems to allow direct 9-1-1 dialing without a prefix and to notify a central location when a 9-1-1 call is placed. 
• LIS: Location Information Server. A repository that maps calling-device reference values, like an IP address, to geographic locations. 
• LNG: Legacy Network Gateway. The functional element that connects a non-IP originating network to an NG9-1-1 system. 
• LoST: Location to Service Translation. The protocol that takes location information and a service URN and returns the URI of the right destination. 
• LPG: Legacy PSAP Gateway. The signaling and media interconnection point between an ESInet and a legacy PSAP. 
• LSRG: Legacy Selective Router Gateway. The interface that routes or transfers calls between legacy and NG9-1-1 networks. 
• LUCA: Local Update of Census Addresses. The program through which tribal, state, and local governments review and correct the Census Bureau’s residential address list before each decennial count.
• LVF: Location Validation Function. The functional element that validates civic location information against the authoritative GIS database; requires road centerlines and address points. 
• Match rate: The share of records in one system that find a corresponding record in another, such as MSAG or ALI records matched to GIS. NENA recommends a 98 percent match rate as a readiness benchmark. 
• MLTS: Multi-Line Telephone System. A phone system serving many users at one site, such as an office, hotel, or campus. Federal rules require MLTS 9-1-1 calls to convey dispatchable location. 
• MSAG: Master Street Address Guide. The tabular database of street names and address ranges that legacy 9-1-1 uses to validate an address and route a call to the correct answering point. 
• National Address Database (NAD): A U.S. Department of Transportation program that compiles address points contributed by state, local, and tribal governments into one public dataset. 
• NENA: National Emergency Number Association. The standards body for 9-1-1 in the United States. It publishes the data models, standards, and information documents that define how address data is structured for NG9-1-1. 
• NENA i3: The NENA standard (NENA-STA-010) defining the architecture of NG9-1-1, including the functional elements that validate locations and route calls. 
• NG9-1-1: Next Generation 9-1-1. The IP-based successor to legacy 9-1-1, which routes calls using GIS data instead of tabular address records and accepts text, images, and data alongside voice. 
• NG9-1-1 GIS Data Model: The NENA standard (NENA-STA-006) specifying the layers, fields, and formats GIS data must follow to support NG9-1-1 location validation and call routing. 
• NGCS: Next Generation Core Services. The set of NG9-1-1 functions, including the ECRF, LVF, and ESRP, that validate locations and route calls across the ESInet. 
• Parcel: A tax-system record of a legally defined piece of land. Parcel and assessor data often hold addresses that GIS and 9-1-1 systems lack, which makes them a standard comparison source. 
• PIDF-LO: Presence Information Data Format, Location Object. The IETF format (RFC 4119, updated by RFC 5491) that carries a caller’s civic or geodetic location with an NG9-1-1 call.
• PRF: Policy Routing Function. The ESRP component that determines the next hop in the call’s signaling path using policy. 
• Provisioning Boundary: The geographic area of GIS data a 9-1-1 authority is responsible for maintaining. 
• PSAP: Public Safety Answering Point. The center that answers 9-1-1 calls for a given area and dispatches or transfers them. Commonly called a 9-1-1 center or dispatch center. 
• QA/QC: Quality Assurance / Quality Control. QA maintains data at a required quality level through each step of preparation; QC is the system of checks applied during development. 
• RAY BAUM’S Act: Federal law (2018) directing the FCC to require that 9-1-1 calls convey the caller’s dispatchable location. FCC rules implementing it apply to multi-line telephone systems and other calling services. 
• RMS: Records Management System. The system of record for police, fire, or EMS case files. It stores addresses tied to open and closed incidents, which is why it often retains values other systems have retired. 
• Road Centerline (RCL): A GIS line representing the center of a road, carrying street name and address range attributes. A required NG9-1-1 layer used to validate and locate addresses where no address point exists. 
• SI: Spatial Interface. The functional element that provisions a 9-1-1 authority’s GIS data into the ECRF and LVF. 
• Site/Structure Address Point (SSAP): A GIS point marking the location of an addressed site or structure, with its full civic address as attributes. One of the required layers in the NENA NG9-1-1 GIS Data Model, and the layer address comparisons are measured against. 
• Subaddress: The part of an address that identifies a unit within a site, such as an apartment, suite, floor, or building number. The NENA NG9-1-1 GIS Data Model carries these as separate address point attributes. 
• Telecommunicator: The NENA term for the professional who answers 9-1-1 calls and dispatches responders. 
• Topology: The rules governing how GIS features connect and relate, such as road segments meeting at intersections or boundaries sharing edges without gaps or overlaps. NG9-1-1 call routing depends on clean topology. 
• URI: Uniform Resource Identifier. A predictably formatted string used to identify a resource on a network.
• URN: Uniform Resource Name. A location-independent identifier designed to stay unique and persistent over long periods. 
• VoIP: Voice over Internet Protocol. Technology that delivers real-time voice and multimedia sessions over IP networks. 
• Weighted confidence scoring: The method ACE uses to rank address candidates. Each candidate receives a score based on the strength and consistency of its supporting data sources, and agreement among independent sources raises it. No NG9-1-1 standard defines a confidence score.
• Z-axis: The vertical component of a caller’s location, such as height above ground or floor level. FCC wireless location rules require carriers to provide z-axis information for 9-1-1 calls.

Last reviewed October 2026

Missing a term your team uses? Suggest it to our public safety GIS team.