The Vertical Challenge of Low-Altitude Economy: Why We Need a Unified Height System?

TL;DR

The paper advocates for adopting Height Above Ellipsoid (HAE) as a unified vertical reference for low-altitude airspace to improve safety, interoperability, and capacity in the rapidly growing low-altitude economy.

Contribution

It introduces HAE as a globally consistent, GNSS-native vertical reference and provides a transformation framework, demonstrated through real-world implementation and risk assessment.

Findings

Transitioning to HAE reduces vertical separation requirements.

Implementing HAE increases airspace capacity.

The framework ensures compatibility with legacy systems.

Abstract

The explosive growth of the low-altitude economy, driven by eVTOLs and UAVs, demands a unified digital infrastructure to ensure safety and scalability. However, the current aviation vertical references are dangerously fragmented: manned aviation relies on barometric pressure, cartography uses Mean Sea Level (MSL), and obstacle avoidance depends on Above Ground Level (AGL). This fragmentation creates significant ambiguity for autonomous systems and hinders cross-stakeholder interoperability. In this article, we propose Height Above Ellipsoid (HAE) as the standardized vertical reference for lower airspace. Unlike legacy systems prone to environmental drift and inconsistent datums, HAE provides a globally consistent, GNSS-native, and mathematically stable reference. We present a pragmatic bidirectional transformation framework to bridge HAE with legacy systems and demonstrate its efficacy through (1) real-world implementation in Shenzhen's partitioned airspace management, and (2) a probabilistic risk assessment driven by empirical flight logs from the PX4 ecosystem. Results show that transitioning to HAE reduces the required vertical separation minimum, effectively increasing dynamic airspace capacity while maintaining a target safety level. This work offers a roadmap for transitioning from analog height keeping to a digital-native vertical standard.