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Geodetic Integrated Monitoring System

Periodic Reporting for period 2 - GIMS (Geodetic Integrated Monitoring System)

Période du rapport: 2019-05-01 au 2021-01-31

The sensitivity of many areas in Europe, as well as around the world, to landslide hazards puts forward the need for an integrated and cost-effective geodetic monitoring capability. The purpose is to have detailed and timely knowledge of the geophysical behaviour of parts of the Earth surface, and its hindrances on structures, in order to mitigate casualties and injuries to the population, and better plan maintenance intervention.

The advent of the Galileo and Sentinel satellites, and their integration with miniaturized in-situ sensors, enables new advanced monitoring solutions which are both cost-effective and highly accurate. Recent experiences showed that a millimetric accuracy on a daily basis is achievable using mass-market single-frequency GPS receivers when in specific operational conditions, such as large visibility of the sky and the presence of a reference station very close to these receivers. With the advent of Galileo, such conditions can be considerably softened because a larger number of visible satellites increases the geometry of the positioning. Moreover, the availability of the Sentinel 1A and 1B SAR data, which are provided with an open and free access policy, allows the usage of SAR images for ground monitoring purposes at a lower cost compared to a few years ago. Finally, the miniaturization of sensors like linear accelerometers, angular rate sensors, thermometers, etc. allows for the deployment of a large number of measuring devices provided that their observations, usually highly affected by severe drifts but moderate noise, can be properly processed.

The main objective of the GIMS project was to build and commercialize an advanced low-cost system based on EGNSS, Copernicus SAR and other in-situ sensors, like inertial measurement units, for the purpose of monitoring ground deformations with a focus on landslides.

The GIMS hardware and software components were designed, produced and deployed in operational monitoring scenarios. The GIMS units deployed at the two test sites in Slovenia were useful to detect the undergoing movements affecting the two landslides, as well as their responses to external drivers such as intense rainfall. The system recovered deformations with millimetric level accuracies and daily acquisition rate. Moreover, the integration of in-situ accelerometers allowed for analyses of sudden movements.

The GIMS project was active from November 2017 to January 2021. All in all, we have learned that even very small signals can be detected by the integrated GIMS system, giving information and alarms, in the form of a GIMS service, to public/private companies interested in mitigating geological risks of landslides.
The GIMS project activities started with a thorough analysis of the user needs and requirements, carried out by the Geological Survey of Slovenia (GeoZS), in collaboration with all the other partners. The various types of landslides were overviewed, as well as the currently used monitoring technologies. The characteristics of the geodetic techniques implemented in GIMS as regards landslide monitoring were outlined by the competent partners. Based on all this information, two experiment sites for GIMS were selected, both in Slovenia.

GReD implemented an ad-hoc GNSS software able to exploit the new dual-frequency EGNSS receivers for geodetic monitoring, achieving millimeter-level precision. In collaboration with CTTC, GReD studied, designed, and implemented also software that integrates GNSS e and SAR results, exploiting the synergy between the two technologies.

Saphyrion designed and produced the GIMS stations, including the dual-frequency low-cost EGNSS receiver, a low-cost inclinometer, a low-cost IMU, and all needed components (e.g. photovoltaic panels, batteries, modems, etc).

GeoNumerics developed the IMU analysis software component of the GIMS system.

CTTC designed and developed a new low-cost active SAR transponder and enhanced their SAR processing tools for the estimation of land deformation maps.

GeoZS brought to the project direct user needs and evaluated practical capabilities and limitations of GIMS units by field implementation and validation of the data.

ComoNExT, as an innovation-oriented science and technology park, supported the coordinator GReD in administration tasks and lead the dissemination and communications activities, as well as the exploitation activities including IPR management, production of a business plan, and management of meetings with potential clients.

GIMS units comprising 7 EGNSS receivers+antennas, 7 IMUs, 7 inclinometers and 2 active SAR transponders were installed at the first test site, in SW Slovenia. A second batch of 7 EGNSS receivers+antennas, 7 IMUs, 7 inclinometers, without active SAR transponders were installed at the second test site, again in Slovenia.

The two test sites were monitored for about 1 year, highlighting some interesting landslide features. For example, An interesting characteristic that could be detected thanks to the low-cost GNSS sensors is the direct correlation between surface displacement and rainfall. It indicates that the area of the deep-seated landslide around a specific monitoring unit is dominated by shallow processes which quickly respond to rain events, as opposed to other parts of the landslide. The time series of the data shows that the lowest part of the landslide is very sensitive to the amount and type of precipitation and constantly adapts the displacement to environmental conditions.
The state-of-the-art before GIMS, regarding EGNSS, SAR and IMU/MEMS technologies for landslide monitoring, is that GNSS (actually GPS) and InSAR are typically used in a separate fashion, and deploying high-level instrumentation, with a relatively high cost.

The GIMS project built on the idea of an integrated approach with the following improved characteristics:
- a new low-cost EGNSS monitoring station (receiver + antenna + transmission + photovoltaic power) was developed, capable of tracking GPS and Galileo on two frequencies;
- a new low-cost SAR active antenna was designed, produced and tested;
- a new open-source GNSS processing software has been developed, specifically for the GIMS purposes;
- low-cost MEMS have been integrated into the monitoring unit, and the corresponding sudden motion alarm software was developed;
- a software for the integration of GNSS-SAR tropospheric corrections was developed.

The system was refined into a pre-marketable solution. After thorough validation, the GIMS system was released to the market for potential customers to use in geohazard monitoring and could serve as an early-warning system. GIMS units will contribute to the detailed and timely knowledge of the landslides motion behaviour, improved planning maintenance intervention and mitigation of casualties and injuries caused to the population and better plan maintenance intervention.

The combination of monitoring of both landslides and infrastructures has, of course, an important socio-economic impact to mitigate risks related to catastrophic failures. This is true not only for landslides and bridges, as demonstrated by GIMS, but in a much wider frame including for example dams, penstocks, pipelines, land subsidence, river embankments, etc.
GIMS station deployed at the first test site, with EGNSS, IMU and inclinometer
GIMS station deployed at the first test site, with EGNSS, active SAR antenna, IMU and inclinometer