From satellite signals to environmental risk maps: Students at the National University of Life and Environmental Sciences of Ukraine are learning about InSAR and APSIS™
As part of the Ukrainian Science and Technology Centre’s project ‘Identification of military and man-made soil and water contamination in post-war landscapes’, the National University of Life and Environmental Sciences of Ukraine hosted the second online course — ‘In-depth course on InSAR processing methodologies and the software used’. The training formed part of the research team’s ongoing systematic preparation for the application of modern satellite technologies to analyse ground surface deformations, conduct spatial diagnostics of hazardous processes and assess environmental risks.
The course was attended by academic and teaching staff, postgraduate students and early-career researchers from the National University of Life and Environmental Sciences of Ukraine. Particular attention was paid to Master’s students on the vocational programmes ‘Soil Conservation and Restoration Technologies’ and ‘Agrochemical Services in Precision Agriculture’. Such competencies are particularly important for future specialists, as modern land assessment is increasingly based on a combination of field observations, laboratory analysis, GIS and remote sensing.
Теоретичний блок курсу провели фахівці Terra Motion Limited. Учасники послідовно розглянули фізичні основи інтерферометрії радарів із синтезованою апертурою — InSAR. На відміну від оптичного знімання, радарний супутник реєструє не лише амплітуду відбитого сигналу, а й його фазу. Порівняння фаз повторних супутникових спостережень дає змогу виявляти надзвичайно малі зміни відстані між сенсором і земною поверхнею та, відповідно, фіксувати осідання або підняття території із субсантиметровою, а за сприятливих умов — міліметровою точністю.
During the course, the entire process of generating an interferometric product was examined in detail: working with Single Look Complex data, image co-registration, interferogram construction, removal of the ‘flat Earth’ and topographic components, phase unwrapping, the use of digital elevation models, and the transition to DInSAR differential interferometry. Considerable attention is paid to sources of error — orbital inaccuracies, digital elevation model errors, atmospheric delays, and spatial and temporal decorrelation. It is precisely an understanding of these factors that enables one to distinguish real deformation from processing artefacts and to interpret time series correctly.
A separate section of the presentation focused on the classic multi-temporal methods PSInSAR and SBAS. These have proven their worth in urban areas, at industrial sites and in areas with stable radar reflectors. At the same time, their application on agricultural land, natural vegetation, forests and peatlands is often complicated by unstable signal coherence, which varies under the influence of plant growth, moisture, snow cover and weather conditions. For projects relating to soils and post-war landscapes, this is a fundamental limitation, as it is precisely outside built-up areas that the most comprehensive spatial coverage needs to be obtained.
The introduction to APSIS™ technology proved particularly interesting. Its key distinction lies in the use not only of continuously coherent points, but also of interferometric pairs in which sufficient signal quality arises periodically. Given a large archive of satellite images, the system cycles through additional combinations of pairs and ‘reconstructs’ the broken interferometric network. This makes it possible to obtain pixel-oriented raster maps of ground surface movements with improved coverage of rural, natural and vegetated areas, and to integrate the results directly into a GIS.
The practical value of the technology was demonstrated through international case studies. Participants examined the monitoring of post-mining areas in the UK, the assessment of ground uplift resulting from the restoration of mine water levels, the analysis of deformations in the Donetsk coalfield – particularly in the vicinity of the ‘Yunkom’ mine – as well as remote diagnostics of the condition of peatlands and the monitoring of hazardous processes at tailings ponds. These examples convincingly demonstrate that InSAR time series can serve not only as a map of displacements but also as an indicator of hidden hydrogeological, geomechanical and environmental changes.
For the study of post-war landscapes, InSAR and APSIS™ technologies offer the opportunity to move from one-off observations to systematic remote monitoring. Deformation rate maps can help to identify subsidence, uplift and local surface instability; monitor areas where groundwater or mine water levels are changing; identify areas of potential contaminant spread; and justify the location of soil and water sampling points. Combining such data with the results of chemical analysis, field surveys and spatial modelling improves the reliability of risk assessments and enables areas to be prioritised for further investigation.
A key outcome of the course was the development of a comprehensive understanding that satellite interferometry is not a standalone cartographic tool, but rather a component of an integrated environmental monitoring system. It combines radar signal physics, mathematical processing of time series, geoinformation analysis and subject-specific interpretation of processes within the ‘soil–water–relief–anthropogenic load’ system.
Lively discussions between participants and lecturers helped to better understand the practical aspects of applying InSAR and to identify areas for its use in researching soil contamination in Ukraine.
The delivery of this second online course strengthens the scientific and educational capacity of the National University of Life and Environmental Sciences of Ukraine and expands the research team’s capabilities in the application of cutting-edge geospatial technologies. The knowledge gained will be utilised in the implementation of the UNTC project, the training of young researchers and master’s students, and the further development of methodologies for remote diagnosis, monitoring and restoration of land affected by military and man-made impacts.