Summaries and Recommendations of the Fringe 2007 Workshop
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Seed Questions
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Seed Questions

Methodology: General - Session

  1. Methodology and techniques applied to archived images:
    1. How to fully exploit ERS and Envisat archives?
    2. In particular, what are the strategies for exploiting ERS2 high DC data?
  2. Methodology and techniques applied to data acquired by new sensors (terra-sar x, cosmo sky-med, alos, .):
    1. Are there new applications that become possible by exploiting the higher resolutions of Terra-SAR-X and Cosmo SkyMed sensors? Will the availability of a constellation of SAR satellites (i.e. the four Cosmo- Skymed satellites) open new possibilities and applications, thanks for example to the shorter revisit time?
    2. Are new studies necessary to fully exploit the higher resolution of new sensors? Can automatic recognition of objects become potentially feasible in high resolution SAR images? And, consequently, is research in this field needed?
    3. In preparation for new SAR data, which is the added value of simulations with respect to the existent data? Have multiple reflections in urban areas to be better investigated in order to exploit high resolution SAR images?
    4. How should frequency and band be selected for optimizing urban SAR tomography? Which is the most suitable system among the existent ones? Can SAR tomography be useful for glaciers monitoring or other "volumetric" applications?
    5. Which are the potential and limitations of the different bands, frequencies and polarizations for forest and other applications?
  3. Methodology and techniques applied to data acquired by future multistatic and/or multichannel sensors (TanDEM-X, ASI Sabrina? .):
    1. Data from future bistatic and/or bichannel SAR missions (TanDEM-X, ASI Sabrina?) can be valuable for SAR tomography, polarimetry, polinsar, enhanced resolution or swath, interference filtering ,etc. (in addition of course to across and along-track interferometry)?
    2. Multistatic and multichannel SAR data would allow new important applications? Having in mind a very limited budget for future simple missions, what features are mandatory and what can be avoided?

DInSAR/PSI Session

  1. Should persistent scatterer (full resolution) and coherence(multilooked)-based methods be considered as independent or complementary means of extracting information from satellite SAR data?
  2. What are the main bottlenecks in terms of quality assessments for the various techniques?
  3. Is it possible to make generic statements on the quality of the estimated deformation parameters, independent of the area of interest, or are these always case study dependent?
  4. How should the trade-off between point density and quality be considered?
  5. How can we parameterize the information content of PS time series? (to interpret time series different from linear velocity model)
  6. How should advanced DInSAR algorithms benefit from spatial + temporal phase unwrapping?

EQs and Tectonics Session

  1. With more than a decade of operation of C-band radar (ERS/ENVISAT/RADARSAT), InSAR measurements of ground deformation have improved in accuracy and its assessment has to be re-evaluated.
    1. What is the smallest ground deformation signal that can be measured with InSAR? Over what spatial and temporal scale?
  2. Long temporal series of radar data allows scientists to estimate rates and changes in rates of slow deformation processes using approaches such as SBAS and PS.
    1. What is the accuracy on constant rate estimates?
    2. What level of rate change can be estimated? Over what time scale?
  3. With displacement and rate estimate errors we currently achieve, what are the deformation processes that we can reliably resolve? (Fault slip/creep, poro-elastic deformation, visco-elastic relaxation, dyke expansion, magma chamber inflation/deflation).
    1. Can the trade-off between competitive processes (e.g., after-slip and visco-elastic relaxation) be resolved with InSAR monitoring of post-seismic movement?
  4. The phase propagation delay through the troposphere has been identified as the main source of error for ground deformation measurements.
    1. What recent developments have we achieved with the use of ancillary data such as the MERIS or GPS nadir delay maps etc.?
    2. Can long temporal data series help characterize the tropospheric signal?
  5. How does the multi-directional observations (ascending/descending, near/far range) help constrain the source parameters (geometry of faults and slip direction)?
  6. What is the advantage of scan-SAR interferometry? What can we observe with scan-InSAR that was not accessible to conventional InSAR? Should scan-SAR become the background mode of data acquisition for surveillance purposes?

Volcanoes - Session

  1. The number of volcanoes studied has increased with respect to past Fringe workshops; the coverage is worldwide (the oral presentations or posters report the results of studies on volcanoes of all continents, except Asia). Is SAR Interferometry ready for an effective global monitoring of volcanic activity? If not, what improvements are desirable (e.g. new missions to reduce revisit times? Improvements in the algorithms? Improvements in the sensors?)
  2. Several abstracts report studies based on the integration of multi- sensors (e.g. ERS1/2 and ENVISAT or ERS1/2, ENVISAT, RADARSAT, ALOS) or multi-swaths dataset. Are the current datasets satisfactory? Are multi- sensor and/or multi-swaths analyses required to improve our knowledge of the volcanoes? Is it necessary that the Agencies modify their data acquisition "policy" in order to expand the type of the images available to study/monitor the volcanoes?
  3. In recent years several techniques to process InSAR time series have been implemented. Is this now a standard technique that for volcano analysis? If not, what are the main limitations to these methods? And what are their requirements in terms of data acquisition strategies?
  4. What is the current state-of-the-art in volcano modeling? Recent studies using open-source software packages, such as PyLith, promise to make such modeling the new standard - is it time to put together a "cookbook" set of software for routinely generating 3D FEM solutions? (i.e. input topo, structure, boundary conditions, source properties and easily generate Greens functions?). More generally, has numerical modeling definitively replaced the analytical approaches?
  5. What are the limitations for detecting small time/spatial scale events with InSAR (TerraSAR X/CosmosSkyMED)?
  6. What is the current state-of-the-art in the integration between the DInSAR measurements of deformations and the results of geodetic surveys or permanent networks?

PSI Validation - Session

  1. Can we define the "error bars" to be associated with deformation velocity; deformation time series; and PS geo-location?
  2. Can we define the conditions to be fulfilled to achieve the above "error bars": number of images, deformation pattern and magnitude, deformation rates, etc.
  3. How can we handle the spatially wide trends (tilts) in the data, which are due to residual orbit?
  4. Can we characterize the PSI capability to detect deformation phenomena (e.g. in urban areas) in terms of omission and false alarms?
  5. Can we expect significant improvements in the measurement of non-linear deformations?

Atmosphere Session

  1. Do we feel that the problem of atmospheric delay signal in SAR interferometric approaches is well-understood?
  2. We distinguish effects of (i) vertical stratification, of importance in case of strong topographic height differences, and (ii) turbulent mixing. Should both effects be tackled independently?
  3. Is it possible to uniquely identify a spatially correlated interferometric phase error due to ionosphere using current sensors? If yes, which empirical evidence is available?
  4. What is the value of Numerical Weather Models for (i) local case studies, and (ii) systematic correction of APS irrespective of location and time
  5. What is the value of the interferometrically derived atmospheric phase screen for operational meteorology and atmospheric research?

Airborne and GB-InSAR - Session

  1. Should Airborne, Ground-Based, and spaceborne InSAR be considered as complementary techniques to orbital InSAR?
  2. Which scenarios/problems are more suited for Airborne and Ground-Based InSAR?
  3. Are the different SAR platforms (orbital, airborne and ground-based) providing interferometric products of similar quality?
  4. Which are the main advantages and limitations of InSAR applications based on airborne and ground-based platforms?
  5. What's the future of bistatic/multistatic SAR in interferometric applications?
  6. What are the future perspective, and expected results in the research on tomography in L band and P band airborne and spaceborne systems?

Interferometry and New Missions Session


  1. Future SAR missions are planned for the time frame 2010++. Are those missions sufficient to satisfy the future needs? If not what is missing. Are there too many? Why?
  2. Future missions are based on experience gained with data from existing missions in space and/or airborne experiments at different wavelength. What are the preferred wavelengths for interferometry applications in order of priority and why?
  3. Are there critical minimum repeat intervals required for the future? Minimum operational life time? For which application?
  4. Future operational missions are likely to produce massive data volumes. What processing level would be preferred for the future? Un-compressed data (level-0), complex single look (level-1) products or interpreted data such as subsidence maps (level-2), or else?
  5. What additional ancillary data (e.g. about baseline information, coherence) should future missions add to their standard products?

Terrain subsidence and Landslides Session

  1. Maturity of techniques and required improvements: What is the maturity of the InSAR retrieval techniques for terrain motion monitoring and which methodological developments would help to improve the InSAR products?
  2. Status of acceptance: What is the status of the acceptance of SAR interferometric techniques and of information derived using these methods in the "user community" and which measures can be taken to enhance the acceptance (qualification, presentation of results, integration, .)?
  3. Future systems: What is the preferred configuration and operation mode of a satellite constellation for operational monitoring services (SAR frequency, spatial resolution, repeat cycle etc.)?
  4. Recommendations: are there any recommendations related to
    1. future studies,
    2. the Envisat mission,
    3. the ALOS mission,
    4. future missions, or
    5. other?


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