Integrated Interferometry and GNSS for Precision Survey
Background & Objectives
In November 2000, a 1.2 million m³ landslide slid down from Stože Mountain in North West Slovenia. It partly or totally destroyed 23 buildings and killed seven people. Potential mass debris flows of a similar size are present in many locations across Europe and present a hazard to citizens.
Identifying the precursors of such events requires very high precision measurements of vertical and horizontal displacements, which need the use of both radar interferometry (to provide vertical displacements) and GNSS measurements (to provide temporal interpolation and horizontal displacements). Geological Survey of Slovenia have identified a large number of vulnerable sites and the potential benefit of using InSAR and GNSS measurements together to identify landslide precursors.
Efforts to perform trials with corner reflectors (as persistent scatterers) and GNSS receivers have been only partially successful because of the difficulty to co-register results and the practical difficulties in deploying the equipment successively in precisely the same location.
The scope of the project can be summarised in three elements:
- developing an integrated GNSS and CAT unit suitable for use in the field trial;
- developing the integrated GNSS and InSAR processing algorithms to exploit this technology;
- validating the practical use of the equipment and processing developed in a controlled calibration environment and responding to specific user needs in field trials.
The approach of the study will be to establish the user requirement vis-à-vis the current state of the art and determine the extent of integration required. Field prototype units will be developed to support field trials.
The field trials will enable the technology to be validated in three distinct environments:
- a controlled calibration site at the Technical University of Delft;
- on an active fault near Postojna (SI), where displacement can be anticipated, to demonstrate the performance of the unit;
- a real landslide risk site, at Stože (SI), where the capacity to detect pre-cursor displacements can be assessed.
The results of the demonstration will be evaluated and reported to a user seminar. A demonstration I2GPS unit will be refined, based upon the results.
I2GPS will develop a novel, integrated approach for the use of synthetic aperture radar interferometry (InSAR data from GMES) and GNSS for use in the monitoring of subsidence, tectonic changes or other environmental hazards, which can only be identified by millimetric precision survey techniques.
I2GPS proposes to deliver a fully integrated unit and end-to-end application for generating co-registered SAR interferometric and GNSS precision survey results by:
- integrating the antenna of a GNSS receiver with a Compact Active Transponder antenna to ensure millimetric co-registration and assure a coherent cross reference between the two precision surveying techniques, with unit verification confirmed at the mid-term review;
- developing the integrated application processing and conducting field trials to confirm the effectiveness of the technique, to be reported at the final review;
- preparing a business plan for exploiting the resulting product and reporting the results to the user community, thereby increasing the use of GNSS and GMES.
Work performed & results
The project will result in the following elements:
- a fully functional prototype, which can be rapidly developed to support early field trials;
- a demonstrator unit achieving a design more suited to final production;
- the infrastructure necessary for supporting the programming of these units and field data collection;
- the novel processing techniques for the integrated use of the resulting GNSS measurements and synthetic aperture radar interferometry results;
- the results of field trials on calibration and real target sites.
The project will also evaluate the potential use of EGNOS, EDAS and Galileo to improve I2GPS results and will prepare a business plan for the exploitation of the project results. A final workshop will present the conclusions to a wider potential user community.
The main aspiration of the project is that the development of this technology may allow the residents of villages, such as Stože which is located close to severe landslide risks, to sleep more safely in their beds.