Local Co-ordinates

Description

Local Co-ordinates is a concept introduced in 3GPP Release 19 to support advanced location services in the 5G System (5GS). In traditional cellular positioning, geographic coordinates are expressed in the World Geodetic System 1984 (WGS84), which provides a global reference frame suitable for outdoor positioning. However, in many indoor and localized scenarios—such as factory floors, shopping malls, or campuses—WGS84 coordinates can be imprecise, difficult to obtain, or not meaningful for applications that require relative positioning. Local Co-ordinates address this by defining a local Cartesian coordinate system whose origin is a reference point, which itself may have known WGS84 coordinates. This allows devices and applications to use a local coordinate frame that is more intuitive and accurate for the specific environment.

The concept is specified in 3GPP TS 23.032 (Universal Geographical Area Description) and TS 23.273 (5G System Location Services). Local Co-ordinates are only applicable in 5GS, meaning they are not defined for earlier generations like LTE or UMTS. The local Cartesian system is defined by a reference point (origin) and potentially orientation parameters. The origin may be provided as WGS84 coordinates, enabling mapping between local and global frames. This is particularly useful for location-based services (LBS) in 5G, such as asset tracking in smart factories, indoor navigation, and augmented reality applications.

The architecture for supporting Local Co-ordinates involves the Location Management Function (LMF) in the 5G core network, which is responsible for determining the location of a UE. The LMF can provide location estimates in various formats, including local coordinates, based on the requested quality of service (QoS) and the capabilities of the UE and network. The UE may also report its location using local coordinates if it has the capability to compute them, for example via internal sensors or assistance data from the network. The 5G Location Services (LCS) framework supports both UE-assisted and UE-based positioning modes, and Local Co-ordinates can be used in either mode.

To use Local Co-ordinates, the network and UE must agree on the local coordinate system definition. This could be pre-configured or negotiated during the location session. The reference point (origin) and the orientation of the axes (e.g., north-aligned or arbitrary) are part of the system definition. The coordinate values are typically expressed in meters or other units relative to the origin. The LMF may provide the UE with assistance data including the local coordinate system parameters to enable the UE to compute its position in that frame.

The introduction of Local Co-ordinates in Rel-19 reflects the growing demand for precise positioning in 5G, especially for vertical industries like manufacturing, logistics, and healthcare. By supporting local coordinate systems, 3GPP enables seamless integration with indoor mapping and navigation systems that often use local frames. It also facilitates the development of location-based applications that require relative positioning, such as collision avoidance for drones or automated guided vehicles (AGVs) in a warehouse. The feature is expected to enhance the value of 5G positioning services and drive innovation in location-aware applications.

Purpose & Motivation

Local Co-ordinates were created to address the limitations of using global coordinate systems like WGS84 in indoor and localized environments. In such environments, WGS84 coordinates may have high uncertainty due to poor GNSS reception and multipath, or they may be overkill for applications that only need relative positions. For example, in a factory, a robot needs to know its position relative to a conveyor belt, not its latitude and longitude. Local Co-ordinates provide a standardized way to express positions in a local Cartesian frame, making it easier for applications to consume and process location data.

The motivation also stems from the need for interoperability across different positioning technologies and vendors. By defining a standard format for local coordinates in 3GPP specifications, the industry can ensure that devices and location servers from different vendors can exchange location information seamlessly. This is particularly important for 5G, which aims to support a wide range of vertical use cases with stringent positioning requirements, such as sub-meter accuracy in indoor environments.

Historically, location services in 3GPP were primarily based on WGS84, with some support for local coordinates in specific verticals like the Local Area Network (LAN) in 5G. However, the formal introduction of Local Co-ordinates in Rel-19 provides a unified framework within the 5G LCS architecture. This allows operators to offer location services that are tailored to the needs of enterprises, enabling new business models and services. The feature also aligns with the broader trend of integrating 5G with Industry 4.0 and smart city initiatives, where precise local positioning is a key enabler.