• Created by Teun Hendriks 

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Proposal 1 (item before meeting14 Apr 2026 )

Short Summary Answer

GERS is a Global Entity Referencing System that assigns stable, long‑lived identifiers to real‑world transportation entities, such as road segments. It enables consistent matching and integration of geospatial data across different digital maps and versions, reduces fragmentation caused by map updates, and supports interoperable data layering across systems and providers.
GERS is developed and governed within the the Overture Maps Foundation, where it is used to provide stable entity identifiers for Overture’s open transportation datasets. At the same time, GERS is designed to be map‑agnostic and reusable beyond Overture: the identifiers can be associated with equivalent entities in other digital maps, allowing datasets referenced via GERS to be exchanged, compared, or integrated across different map ecosystems.

Why the need for a stable global entity reference system?

Digital maps evolve continuously, and their representations change over time. Road geometries may shift, attributes such as speed limits or surface types may change, and modeling rules differ between map providers. As a result, map‑specific identifiers are frequently regenerated, breaking continuity for downstream applications such as traffic management, analytics, or infrastructure monitoring.

Without a stable reference layer, each data update requires repeated and costly re‑matching and conflation, i.e. a process of combining and aligning data from different sources so they refer to the same real‑world object.  A global entity reference system addresses this by providing persistent identifiers that remain stable across map changes, enabling consistent association of data to be associated with the same real‑world entity over time, even as despite evolving map representations evolve.

How does GERS address differences between maps?

Different maps represent the same road in different ways. Segmentation rules, topology, and attribute modeling can vary significantly between providers or even between map versions of the same provider.

GERS addresses these differences by:

• Defining entities using decision‑point‑based segmentation rather than attribute‑driven splitting.
• Preserving identity independently of minor geometric changes.
• Applying linear referencing to model attribute changes without fragmenting the base entity.

This allows different maps to align their data to the same real‑world entity reference, even when their geometries or attributes are not identical.

Stakeholder Relevance / Rationale

Relevance and rationale for using GERS as a stable location referencing method for various stakeholders can be summarized as follows:

• Public Authorities:  Supports interoperable use of road network data across National Access Points, traffic management systems, and analytics platforms; reduces dependency on proprietary map identifiers.
• Content Providers:  Enables stable anchoring of traffic, infrastructure, and regulatory data to real‑world entities across multiple maps and updates; reduces re‑conflation effort.
• Service Providers: Facilitates consistent service behavior across map changes; enables long‑term data reuse and cross‑platform integration.
• OEMs: Supports persistent referencing of ADAS, navigation, and road attribute data across vehicle lifecycles and map updates.

Detailed Explanation

Linear Referencing and Entity Stability

GERS uses linear referencing principles to separate entity identity from attribute variation. Instead of splitting road geometry for every change (e.g. speed, lighting, surface), attributes are referenced along a stable base entity.

This approach provides the following benefits:

• Minimizes identifier churn
• Improves long‑term data consistency
• Reduces downstream recalculation and validation effort

GERS applies a linear referencing–based segmentation approach in which each road is divided into stable, topologically connected sections defined by decision points, rather than by attribute changes. These decision points typically coincide with intersections or locations where a driver can make a routing decision (e.g. merge, diverge), and therefore define natural and stable boundaries in the transport network, see figure below. 

Within this approach, all geometry segments between two decision points are merged into a single GERS entity and assigned a unique identifier. This ensures that a road section remains consistently identifiable over time, independent of how many attributes may change along it. Minor geometric shifts (e.g. due to map updates) do not affect the identity, as long as the topology remains unchanged. By basing segmentation on network topology rather than on attribute variation, GERS creates a stable reference layer that aligns with how users conceptually perceive roads—as connected sections between intersections—while minimizing unnecessary fragmentation of identifiers across map versions and providers. 

GERS assigns IDs to stable topologically connected road sections, i.e. sections between road intersections.

Within each stable GERS section, attribute variation is handled using linear referencing offsets, rather than by splitting the geometry. Instead of assigning a new identifier every time an attribute changes (e.g. speed limit, surface type, lighting), GERS retains a single section ID and expresses changes as positions along that section, see figure below. 

These offsets indicate where along the section an attribute begins and ends. As a result, multiple attribute changes can coexist on the same base entity without affecting its identity. This avoids repeated segmentation and preserves the continuity of the road section, while still allowing precise localization of changes. This separation of entity identity (the section) and attribute variation (offset-based references) reduces identifier churn, avoids costly recalculation of dependent data (such as traffic flow or direction), and supports consistent data association across map updates and datasets.TBD: Explain picture above and below

Offsets within a stable GERS section are used to signify the location of a road attribute change

Tools and Ecosystem Support

GERS is supported by tooling that enables practical adoption:

• Map sectioning services to build consistent base entities

• Entity registries and explorers to inspect GERS IDs

• Global Entity Matching tools (e.g. TomTom GEM) to align external datasets with GERS‑identified entities

These tools allow both public and private datasets to participate in a shared reference framework.  See below in "References and Tools" for links to further information. 

GERSification process

The “GERSification” process refers to the workflow by which external or newly available road network data is aligned with the GERS reference layer and assigned GERS identifiers. This process typically starts by matching incoming geometries against the existing GERS‑based transportation network. Below figure explains the "GERSification process using the TomTom Global Entity Matching processExplanation TBD.

TomTom Global Entity Matcher tool

Where a correspondence is found, the external data can inherit the existing GERS IDs. Where no match exists—indicating missing or newly identified road geometry—the system identifies these gaps and assigns new GERS identifiers to previously unmatched sections, thereby extending the reference network. Once assigned, these GERS identifiers act as stable anchors that enable interoperability with other map ecosystems. The result is that data originally tied to a specific geometry (e.g. latitude/longitude or proprietary IDs) becomes referenced to a shared, map‑agnostic entity layer, enabling integration, exchange, and reuse across platforms.

This process is supported by matching and onboarding tools (such as global entity matching services), which automate the alignment and identifier assignment, ensuring that both public and private datasets can participate in a consistent global referencing framework.

Use Cases

• Traffic and Incident Management: Persistent association of events with road entities across map updates
• Infrastructure Analytics: Long‑term tracking of road attributes and performance
• Data Integration Platforms: Combining datasets from multiple sources without repeated conflation
• Standards and Reference Architectures: Providing a practical model for stable referencing concepts

Technical Considerations

• Map Dependency: GERS is map‑agnostic but requires digital map data to construct and maintain entity definitions.
• Segmentation Rules: Decision‑point‑based segmentation is critical for stability.
• Attribute Modeling: Best results are achieved when attribute changes use linear referencing rather than geometry splitting.
• Governance: Long‑term stability depends on consistent application of modeling rules.

Decision Guide

Implementation Notes

• GERS complements, rather than replaces, dynamic location referencing methods such as OpenLR (see also [TISA-LR-OpenLR-FAQ1] - Why is OpenLR the right location referencing method for us?).
• GERS is best used as a foundational reference layer for storing and integrating geospatial data.
• External datasets should be matched to GERS IDs using dedicated matching tools.
• Attribute changes should be modeled using linear referencing where possible.

References & Tools

For understanding GERS as a method, the following references are useful:

• Home - Overture Maps Foundation

• GERS - Global Entity Reference System | Overture Maps - Overture Maps Foundation

• TomTom Global Entity Matcher (GEM)
• GERS Tutorial | Overture Maps Documentation
• Using the GERS "system" | Overture Maps Documentation

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