FIG Commission 5 - Positioning and Measurement

Working Group 5.3
Vertical Reference Frames

Policy Issues

  • Educate FIG member agencies on current and future status of regional and global vertical reference frames and height systems
  • Educate FIG member agencies on practical aspects about the implementation of new geopotential datums including:
    • access using geoid height models and a geometric datum
    • redefining heights on existing bench marks to serve as secondary control
    • ties between height systems and local and global mean sea level
  • Develop and expand relationships in IAG Commission 2, UN SCOG, and WG focused on implementing vertical control based on IHRF around the world.
    • IAG will develop an IHRF that will be a component of the UN GGRF.
    •  UN GGRF will encompass both ITRF and IHRF
    • Time varying aspects of the geoid, vertical control and the gravity field must be addressed.


David Avalos-Naranjo, Mexico


What we are working on -

  • Inventory/catalogue of height systems and vertical datums in use by countries and/or FIG member agencies
  • Capture planned changes and timelines for the evolution of height systems in countries and by FIG member agencies
  • Provide guidelines to re-define the national vertical control, interpret and access the IHRF.

What's New

In order to provide tools so that geomatics practitioners can effectively understand and use VRF’s in their day to day work or implement VRF’s in their national jurisdictions, this working group has promoted education through participation in the international workshop Reference Frames in Practice, Hanoi, Vietnam, April 20, 2019. This participation helped increase the understanding of modern VRFs and realize the actions needed to relate vertical positioning datasets from different sources. Additionally, during the FIG Working Week 2019, WG5.3 convened a technical session where representatives from 15 countries witnessed and discussed practical aspects of constructing and using vertical reference frames, as well as reviewed the current challenges of switching to modern definitions and more accurate VRFs like the International Height Reference System (IHRS).