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Global Entity Matcher (GEM)

Glossary

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Glossary

Definitions of key terms used throughout the GEM documentation.

A

API Key

A unique identifier used to authenticate requests to TomTom APIs. API keys are managed at my.tomtom.com/keys and must have the appropriate GEM APIs enabled.

Apache Parquet

A columnar storage file format optimized for use with big data processing frameworks. GEM accepts input files in Parquet format; lane-level matching also accepts CSV.

Authorization Token

A temporary Bearer token obtained via Azure CLI that authenticates your identity for GEM API requests. Tokens expire after a set period (typically 1 hour) and must be refreshed.

Azure CLI

Microsoft’s command-line interface for managing Azure resources. GEM uses Azure CLI for data upload and download operations. Install from Microsoft’s documentation.

C

Confidence Score

A numerical value (0-100) indicating how certain GEM is about a match between your road segment and a GERS ID. Higher scores indicate more reliable matches. Scores above 85 are considered excellent.

Conflation

The process of combining geospatial data from different sources, aligning overlapping features, and resolving differences. GEM automates conflation by matching your data to GERS IDs.

G

GEM (Global Entity Matcher)

TomTom’s service that automatically aligns proprietary geospatial datasets with Overture’s Global Entity Reference System (GERS) identifiers.

GERS (Global Entity Reference System)

An open, standardized system developed by the Overture Maps Foundation for uniquely identifying geospatial features like roads, intersections, and places. GERS IDs enable interoperability across different mapping systems.

GERS ID

A unique, persistent identifier assigned to a geospatial feature in the Global Entity Reference System. GERS IDs are UUIDs, for example 0b5c2f4e-8d3a-4c1e-9f6b-2a7d5e8c1b34.

Geometry

The spatial representation of a geographic feature. In road matching, geometries are WKT LineStrings in WGS84 coordinates that represent road segments.

J

Job

A matching request submitted to GEM. Each job processes one input file and produces a results file. See Job status values.

Job Run ID

The unique identifier of a job: job_id in the API, Job Run ID in the UI. Use it to track the status and retrieve the results.

L

Linear Referencing

A method of describing positions along a linear feature (like a road) using distance measurements from a reference point, rather than geographic coordinates. Enables sub-segment level precision. In GEM results, lr_id and lr_gers give the matched part of a line as a percentage range, see Linear references.

LineString

A geometry type representing a path of connected points. In WKT format: LINESTRING (x1 y1, x2 y2, x3 y3). GEM requires road geometries as LineStrings.

M

Matching Type

The kind of matching a job performs: road matching (ROAD_MATCHING) matches road segments to GERS IDs of Overture Maps; lane-level matching (LANE_LEVEL_MATCHING) matches GPS traces to the roads and lanes of TomTom Orbis Maps.

Microsoft Entra ID

Microsoft’s cloud-based identity service (formerly Azure Active Directory). Used for authentication when accessing GEM through the dashboard or API.

N

A property indicating whether a road segment can be traveled by vehicles. Set via the optional is_navigable boolean column of road matching input.

O

Orbis Maps

TomTom’s next-generation map product featuring high-quality, commercially supported map data with GERS ID support.

Overture Maps Foundation

A collaborative initiative to develop open, interoperable map data. The foundation maintains the GERS standard and releases regular map data updates.

Overture Release

A versioned snapshot of Overture Maps data. You choose the release for each road matching job, which keeps the results consistent; the UI preselects the latest release.

P

Parquet

See Apache Parquet.

Private Data Gateway

The TomTom API that manages secure cloud storage for GEM data. Provides endpoints to list storages, get storage details, and obtain credentials.

R

Results File

The Parquet file that a successful job writes next to its input file, named <name>.results.parquet.

Road Segment

A portion of a road network represented as a single feature with a unique ID and geometry. The basic unit of data that GEM processes and matches.

S

Service Principal

An Azure identity used for automated authentication. GEM provides service principal credentials for Azure CLI authentication during data upload/download.

Storage

A secure cloud storage location where you upload input data and download results. Each organization may have one or more storages configured.

Storage Credentials

Temporary authentication credentials (client ID, client secret, tenant ID) used to access storage via Azure CLI. Obtained from the Private Data Gateway API.

T

TomTom API Gateway

The central gateway (api.tomtom.com) through which all TomTom APIs, including GEM, are accessed.

Trace

An ordered sequence of GPS points from one drive. Traces are the input of lane-level matching.

V

Visualization Data

GeoJSON files that a road matching job can write next to its results, for viewing the matches in GIS tools. See Visualization data.

W

WKT (Well-Known Text)

A text markup language for representing geometric objects. GEM uses WKT format for LineString geometries.

Example:

LINESTRING (4.8952 52.3702, 4.8960 52.3710, 4.8975 52.3725)

Format: LINESTRING (longitude1 latitude1, longitude2 latitude2, ...)