The Coordinating Committee is responsible for the coordination of the collection, compilation, use, and dissemination of data related to hydraulics, hydrology, and vertical control for the Great Lakes – St. Lawrence River System. A fundamental requirement for coordinated management is a common height reference system or “vertical datum” by which water levels can be measured and meaningfully related to each other.

The first such vertical datum for the Great Lakes was the International Great Lakes Datum of 1955 (IGLD (1955)). To ensure the vertical datum provides sufficiently accurate heights, it must be adjusted approximately every 30 years to account for the effects of glacial isostatic adjustment (GIA) since the last ice age. GIA is the continuing response of the Earth to the loss of weight of the ice sheets, where areas that were under the ice are rebounding and areas outside the periphery of the ice sheets are subsiding.

IGLD (1955) was updated to IGLD (1985) to account for GIA and, 35 years later, the Coordinating Committee is once again updating IGLD. The Committee’s Vertical Control – Water Levels Subcommittee is overseeing this work and has developed a comprehensive plan. This plan is available in the following three formats:

Full Comprehensive Plan Download

Executive Summary Download

PowerPoint Presentation Download – updated PPT file forthcoming summer 2021

In the years leading up to the release of the new datum, the Coordinating Committee will conduct extensive outreach to discuss the update and the above-linked plan with wider audiences. To facilitate these efforts, a suite of downloadable resources are currently being planned and will be uploaded and announced on this website. These materials are free for public use. Please check back periodically for new resources, event announcements, project reports, and more.

Upcoming Webinars

Designed to engage audiences with presentations and discussions from leading scientists, IGLD webinars focus on methodologies, expected impacts, and ways to prepare for the new datum.

June 17, 2021 from 12:30 – 2:00 PM EDT

Mapping the Great Lakes – Building the Case for Collaboration and Policy Through Data

Presentation: IGLD (2020): Updating the Common Height Reference System for the Great Lakes

Host: The Marine Center, Northwestern Michigan College

Speaker: Jacob Heck (NOAA NGS)


July 15, 2021 from 2:00 – 3:00 PM EDT

Vertical Datums: An Overview and Planned Updates

Host: NOAA’s National Geodetic Survey

Speakers: Terese Herron (DFO CHS), Laura Rear McLaughlin (NOAA CO-OPS), Jacob Heck (NOAA NGS)


Conferences & Summits

Leading up to the rollout of IGLD (2020) in 2025, IGLD will also be presented at several conferences, meetings, seminars, and summits. If you are attending any of the following events, please join us at our session/presentation!

May 17-21, 2021

IAGLR’s 64th Annual Conference on Great Lakes Research

Presentation: Lake Surface Topography from Water Gauging, GNSS Observations and Gravimetric Geopotential Models

Host: International Association for Great Lakes Research

Speakers: Dan Roman (NOAA), Marc Véronneau (CGS), John Crowley (NRCAN)

Event website

June 20-25, 2021

International Federation of Surveyors (FIG) Working Week 2021 – virtual

Presentation: Updating the International Great Lakes Datum: Enabling the Integration of Water and Land Management in the Great Lakes Region

Host: International Federation of Surveyors (FIG)

Speakers: Jacob Heck (NOAA), Dr. Michael Craymer (CGS)

Event website

September 29 – October 1, 2021

Lakebed 2030 Conference – virtual

Host: Northwestern Michigan College, the Marine Center

Speakers: TBD

Call for Proposals

Technical Reports & Analyses

Regular IGLD (2020) reports will also be issued and posted on this web-page as work progresses on this significant multi-year, multi-agency, multi-national effort.

Last revised: 2021-05-14