Portagauge and Satellite Sea Level Monitoring System for the Southwest Indian Ocean

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PASS-SWIO is a project funded by ESA which aims to establish a sea level monitoring system for Madagascar based on the installation and deployment of a low-cost relocatable tide gauge (Portagauge). Portagauge uses GNSS interferometric reflectometry (GNSS-IR) technology alongside a conventional radar. By combining these measurements with the analysis of satellite altimeter sea level data we will provide validation and wider scale knowledge of sea-level variability.

Madagascar has very limited tidal prediction, primarily based on model data. It has no national sea level monitoring capability. There is currently only one functioning tide gauge station. A previous tide gauge, in the cyclone-prone north of the island, was destroyed several years ago.

The project partners will work with the national Madagascar Meteorological Agency (DGM Direction Generale de la Meteorologie). DGM will take responsibility for the local maintenance and operation of the Portagauge. They will also receive training to carry out the data processing and analysis of tide gauge and satellite altimeter data.

Discussions will be held with key stakeholders to review the project and agree a long-term Road Map for the sustainable implementation of a national sea-level monitoring system for Madagascar. This will serve as model for other island states and coastal countries in the South West Indian Ocean (SWIO) region and beyond.

If you would like to access any of the data sets produced, please contact the Project Manager (see below).

Latest news

Webinar for Users -14 September 2022

An important aspect of PASS-SWIO is to engage with current and potential users of sea level data in Madagascar to understand the main requirements for sea level information, and gaps in current availability.

To support this objective, a webinar will be held on 14th September 1400-1530 EAT (1200-1330 BST). The webinar will introduce the PASS-SWIO project, provide scientific context to sea level change in the South-West Indian Ocean, and introduce an online questionnaire.

For more details click on the links for invitations in English and French.

To register for the webinar go to:

Study area

Madagascar, showing previous, current, and proposed Tide Gauge Locations, and Toamasina Harbour




Project Manager: Amani Becker, NOC (abeck at

Project activities

Work Package 1000 User Engagement & Capacity Building:

  • Training to local DGM staff on Portagauge installation and data processing
  • Engagement with stakeholder agencies in Madagascar
  • Project website with links to data

Work Package 2000 Portagauge Manufacture, Installation & Operation:

  • NOC will finalise the design and manufacture of the Portagauge
  • NOC and SatOC will organise the shipping of the Portagauge to Madagascar and it will be installed at the first site with assistance from DGM
  • Operational monitoring of the instrument and data will be carried out remotely by NOC and in situ by DGM

Work Package 3000 Sea Level Data Processing:

  • Processing and analysis of sea-level data from Portagauge to output quality controlled time series
  • Processing of satellite altimeter data from Jason and Sentinel-3 to output quality controlled along-track Total Water Level Envelope time series
  • Cross-validation of satellite and Portagauge data
  • Analysis of tidal and non-tidal sea level variability characteristics

Work Package 4000 Sustainable Implementation Road Map:

  • Identify and document the requirements for Malagasy sea level monitoring capability through consultation with stakeholders
  • Draft plan of future Portagauge deployment sites in Madagascar
  • Generate road map, with input from stakeholders, for sustainable implementation of sea level monitoring

Key Dates and Meetings

Project Kick Off (May 2022): Planning and confirmation of project timetable

Stakeholder Meeting (June 2022):  (Online meeting) Introduce project, establish requirements for improved sea level monitoring

Portagauge Installation (October 2022):  Installation of Portagauge in Madagascar and training for operation

Mid Term Review (October 2022):  Review of progress, confirm planning for second phase

Training (March 2023): (in Madagascar) Processing, assessment and validation of data from installed portagauge

Stakeholder Meeting (March 2023): (In person) Presentation of project results, discuss recommendations

Final Review (April 2023): Presentation and review of project results

Project team

noc    satoc  


Satellite Oceanographic Consultants Ltd 2022