IAG | 2021-04-20

JWG 1.2.2: Methodology for surveying geodetic instrument reference points

Chair: Ryan Hippenstiel (NOAA/NGS, USA)

Vice-Chair: Sten Bergstrand (BIPM, France)


Terms of Reference

The International Terrestrial Reference System is built upon multiple geodetic techniques; Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), Doppler Orbitography and Radiopositioning Integrated by satellite (DORIS), and Global Navigation Satellite Systems (GNSS).  At locations where these techniques are co-located, it is vital to determine and understand the vectors between the reference points of each technique.  These vectors are determined by local tie surveys conducted terrestrially with various procedures and geodetic instruments.  The reference points should be collected and properly aligned to a global reference frame in order to produce relative and absolute coordinates. 

As the science of local tie surveys has developed, so has technology and the expectation of higher precision and improved protocols.  It is the desire of this working group to investigate the current and expected best practices available, along with documenting past efforts, both in the field and researched.  This working group will share methodology of existing tie surveys, continued to develop and document recommended procedures, and also archive surveys completed by all agencies represented.  In addition, efforts will be made to isolate systematic errors of the space geodetic techniques using surveying methods and investigate field procedures that could be completed during the course of a tie survey in order to provide the operator valuable feedback on potential physical errors found onsite.  One critical example of this is quantifying thermal and gravitational deformation in VLBI sensors.  It is the overall goal of the working group to encourage consistent field practice, terminology, and documentation throughout the community, with a continued eye on the future of tie surveys. 



Enhance and improve knowledge of local tie surveys through applied field practice, research, and dissemination of materials developed. 



 ·          Investigate thermal and gravitational deformation.

·          Consider importance and inclusion of DoV observations.

·          Discuss overall error budget and precision (achieved/necessary) considering the above.

·          Continue to enhance guidelines on procedures (and subsequent feedback for improvement).

·          Archive reports, tie vectors and raw data of all agencies conducting tie surveys.

·          Gather, distribute, and maintain publications on related matters.

·          Coordinate with and solicit feedback from all geodetic techniques on developments.


 ·         Participation in local tie surveys and/or testing of new methodologies.

·         Attendance of meetings or participation in remote/virtual discussions.

·         Reporting of survey results and/or research efforts towards the objectives of the WG.

·         Develop and maintain a depository of past and future reference materials.


List of members

Zuheir Altamimi (France)

Sten Bergstrand (France), Vice-Chair
Steven Breidenbach (USA)

Benjamin Erickson (USA)

Kendall Fancher (USA)

Charles Geoghegan (USA)

Ryan Hippenstiel (USA), Chair

Kevin Jordan (USA)

Jack McCubbine (GA, Australia)

Damien Pesce (IGN, France)

Jerome Saunier (France)


Corresponding members

Xavier Collilieux (France)

Mike Pearlman (Harvard/GGOS, USA)


(the memberlist will be updated as WG develops and member confirmation is received)

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