Suitability of ground-based SfM-MVS for monitoring glacial and periglacial processes

Photo-based surface reconstruction is rapidly emerging as an alternative survey technique to lidar (light detection and ranging) in many fields of geoscience fostered by the recent development of computer vision algorithms such as structure from motion (SfM) and dense image matching such as multi-view stereo (MVS). The objectives of this work are to test the suitability of the ground-based SfM-MVS approach for calculating the geodetic mass balance of a 2.1km2 glacier and for detecting the surface displacement of a neighbouring active rock glacier located in the eastern Italian Alps. The photos were acquired in 2013 and 2014 using a digital consumer-grade camera during single-day field surveys. Airborne laser scanning (ALS, otherwise known as airborne lidar) data were used as benchmarks to estimate the accuracy of the photogrammetric digital elevation models (DEMs) and the reliability of the method. The SfM-MVS approach enabled the reconstruction of high-quality DEMs, which provided estimates of glacial and periglacial processes similar to those achievable using ALS. In stable bedrock areas outside the glacier, the mean and the standard deviation of the elevation difference between the SfM-MVS DEM and the ALS DEM was-0.42 \ub1 1.72 and 0.03 \ub1 0.74 m in 2013 and 2014, respectively. The overall pattern of elevation loss and gain on the glacier were similar with both methods, ranging between-5.53 and + 3.48 m. In the rock glacier area, the elevation difference between the SfM-MVS DEM and the ALS DEM was 0.02 \ub1 0.17 m. The SfM-MVS was able to reproduce the patterns and the magnitudes of displacement of the rock glacier observed by the ALS, ranging between 0.00 and 0.48 m per year. The use of natural targets as ground control points, the occurrence of shadowed and low-contrast areas, and in particular the suboptimal camera network geometry imposed by the morphology of the study area were the main factors affecting the accuracy of photogrammetric DEMs negatively. Technical improvements such as using an aerial platform and/or placing artificial targets could significantly improve the results but run the risk of being more demanding in terms of costs and logistics

Non-financial information as a driver of transformation. Evidence from Italy

The EU Directive on disclosure of non-financial and diversity information (2014/95/EU), transposed in Italy by the Legislative Decree no. 254 of December 30, 2016, in force since January 25, 2017, is contributing to a cultural transformation of corporate governance models. By triggering a growing consideration of all stakeholders’ needs, this transformation may influence the processes at the board level, the behavior of board members as well as companies’ culture, strategy and business models. The 2017 CONSOB Report on Corporate Governance of Italian listed companies provided a first review of governance behavior of Ftse Mib companies on the verge of the 2014/95/EU Directive, focusing on the inclusion of non-financial matters in reporting and at the board level. This Report extends the previous analysis by including all Italian firms with ordinary shares listed on the MTA at the end of 2017 and delving deeper along three dimensions. First, it reviews how Italian listed firms have implemented the Directive 2014/95/UE by referring to the publication of a nonfinancial statement (NFS), whether they have realized the materiality analysis and whether they have applied a process including both an internal and an external assessment. Second, the Report explores whether companies consider non-financial issues relevant also at the board level, by referring to the guidelines issued by companies prior to the 2018 board appointment, the board evaluation process and the board induction programs organised in 2018. Finally, the findings of a survey involving the members of the Italian community of non-executive and independent directors (Nedcommunity) are presented. The documental analysis aimed to ascertain whether non-financial topics are deemed important also for the selection of the board members’, while the survey focused on the independent directors’ engagement in the board activity concerning the governance of non-financial issues and the compliance with the Decree 254/2016.1 The goal of the analysis is to detect whether, beyond compliance, companies reporting on environmental, social and governance (ESG) are also undergoing a strategy and business model transformation. Integration of ESG factors into many different areas of company’s organization and processes may in fact trigger a cultural transformation of governance models: from the company’s purpose to the activation of cross-functional and forward thinking behaviors and projects; the progressive consideration of ESG into monitoring and reporting tools; the engagement with internal and external stakeholders and their contribution in defining the relevance of non-financial issues in the materiality analysis; the inclusion in the risk governance of non-financial risk management. The chart below summarizes and classifies the findings of the analysis by identifying three progressive steps marking the transformation process: awareness, capabilities, engagement.2 The evidence gathered in this Report shows that while a few large companies are now starting to integrate ESG into governance, the majority of firms (predominantly small ones) are still focused on compliance

Three different glacier surges at a spot: what satellites observe and what not

In the Karakoram, dozens of glacier surges occurred in the past 2 decades, making the region a global hotspot. Detailed analyses of dense time series from optical and radar satellite images revealed a wide range of surge behaviour in this region: from slow advances longer than a decade at low flow velocities to short, pulse-like advances over 1 or 2 years with high velocities. In this study, we present an analysis of three currently surging glaciers in the central Karakoram: North and South Chongtar Glaciers and an unnamed glacier referred to as NN9. All three glaciers flow towards the same small region but differ strongly in surge behaviour. A full suite of satellites (e.g. Landsat, Sentinel-1 and 2, Planet, TerraSAR-X, ICESat-2) and digital elevation models (DEMs) from different sources (e.g. Shuttle Radar Topography Mission, SRTM; Satellite Pour l’Observation de la Terre, SPOT; High Mountain Asia DEM, HMA DEM) are used to (a) obtain comprehensive information about the evolution of the surges from 2000 to 2021 and (b) to compare and evaluate capabilities and limitations of the different satellite sensors for monitoring surges of relatively small glaciers in steep terrain. A strongly contrasting evolution of advance rates and flow velocities is found, though the elevation change pattern is more similar. For example, South Chongtar Glacier had short-lived advance rates above 10 km yr−1, velocities up to 30 m d−1, and surface elevations increasing by 170 m. In contrast, the neighbouring and 3-times-smaller North Chongtar Glacier had a slow and near-linear increase in advance rates (up to 500 m yr−1), flow velocities below 1 m d−1 and elevation increases up to 100 m. The even smaller glacier NN9 changed from a slow advance to a full surge within a year, reaching advance rates higher than 1 km yr−1. It seems that, despite a similar climatic setting, different surge mechanisms are at play, and a transition from one mechanism to another can occur during a single surge. The sensor inter-comparison revealed a high agreement across sensors for deriving flow velocities, but limitations are found on small and narrow glaciers in steep terrain, in particular for Sentinel-1. All investigated DEMs have the required accuracy to clearly show the volume changes during the surges, and elevations from ICESat-2 ATL03 data fit neatly to the other DEMs. We conclude that the available satellite data allow for a comprehensive observation of glacier surges from space when combining different sensors to determine the temporal evolution of length, elevation and velocity changes

Long-term monitoring (1953–2019) of geomorphologically active sections of Little Ice Age lateral moraines in the context of changing meteorological conditions

We show a long-term erosion monitoring of several geomorphologically active gully systems on Little Ice Age lateral moraines in the European Central–Eastern Alps, covering a total time period from 1953 to 2019 and including several survey periods in order to identify corresponding morphodynamic trends. For the implementation, DEM (digital elevation model) of Differences (DoDs) were calculated, based on multitemporal high-resolution digital elevation models from historical aerial images (generated by structure from motion photogrammetry with multi-view stereo) and light detection and ranging from airborne platforms. Two approaches were implemented to achieve the corresponding objectives. First, by calculating linear regression models using the accumulated sediment yield and the corresponding catchment area (on a log–log scale), the range of the variability in the spatial distribution of erosion values within the sites. Second, we use volume calculations to determine the total and the mean sediment yield (as well as erosion rates) of the entire sites. Subsequently, both the sites and the different time periods of both approaches are compared. Based on the slopes of the calculated regression lines, it can be shown that the highest variability in the sediment yield at the sites occurs in the first time period (mainly 1950s to 1970s). This can be attributed to the fact that within some sites the sediment yield per square metre increases clearly more strongly (regression lines with slopes up to 1.5). In contrast, in the later time periods (1970s to mid-2000s and mid-2000s to 2017/2019), there is generally a decrease in 10 out of 12 cases (regression lines with slopes around 1). However, even at sites with an increase in the variability in the sediment yield over time, the earlier high variabilities are no longer reached. This means that the spatial pattern of erosion in the gully heads changes over time as it becomes more uniform. Furthermore, using sediment volume calculations and corresponding erosion rates, we show a generally decreasing trend in geomorphic activity (amount of sediment yield) between the different time periods in 10 out of 12 sites, while 2 sites show an opposite trend, where morphodynamics increase and remain at the same level. Finally, we summarise the results of long-term changes in the morphodynamics of geomorphologically active areas on lateral moraines by presenting the “sediment activity concept”, which, in contrast to theoretical models, is based on actually calculated erosion. The level of geomorphic activity depends strongly on the characteristics of the sites, such as size, slope length, and slope gradient, some of which are associated with deeply incised gullies. It is noticeable that especially areas with influence of dead ice over decades in the lower slope area show high geomorphic activity. Furthermore, we show that system internal factors, as well as the general paraglacial adjustment process, have a greater influence on long-term morphodynamics than changing external weather and climate conditions, which, however, had a slight impact mainly in the last, i.e. most recent, time period (mid-2000s to 2017/2019) and may have led to an increase in erosion at the sites

Observing glacier elevation changes from spaceborne optical and radar sensors – an inter-comparison experiment using ASTER and TanDEM-X data

Observations of glacier mass changes are key to understanding the response of glaciers to climate change and related impacts, such as regional runoff, ecosystem changes, and global sea-level rise. Spaceborne optical and radar sensors make it possible to quantify glacier elevation changes, and thus multi-annual mass changes, on a regional and global scale. However, estimates from a growing number of studies show a wide range of results with differences often beyond uncertainty bounds. Here, we present the outcome of a community-based inter-comparison experiment using spaceborne optical stereo (ASTER) and synthetic aperture radar interferometry (TanDEM-X) data to estimate elevation changes for defined glaciers and target periods that pose different assessment challenges. Using provided or self-processed digital elevation models (DEMs) for five test sites, 12 research groups provided a total of 97 spaceborne elevation-change datasets using various processing strategies. Validation with airborne data showed that using an ensemble estimate is promising to reduce random errors from different instruments and processing methods, but still requires a more comprehensive investigation and correction of systematic errors. We found that scene selection, DEM processing, and co-registration have the biggest impact on the results. Other processing steps, such as treating spatial data voids, differences in survey periods, or radar penetration, can still be important for individual cases. Future research should focus on testing different implementations of individual processing steps (e.g. co-registration) and addressing issues related to temporal corrections, radar penetration, glacier area changes, and density conversion. Finally, there is a clear need for our community to develop best practices, use open, reproducible software, and assess overall uncertainty in order to enhance inter-comparison and empower physical process insights across glacier elevation-change studies

THE USE OF STRUCTURE FROM MOTION TECHNOLOGIES FOR HIGH-RESOLUTION TERRAIN MODELLING ON HIGH ALTITUDE CATCHMENTS

The research project developed in this Thesis involves the application of close-range photogrammetry based on the Structure from Motion (SfM) approach that allows reconstructing the 3D point cloud of the photographed object from a sequence of overlapping images taken with a common digital camera. Thanks to the characteristics of high portability of the equipment, flexibility of the method to reconstruct surface at different scale with high resolution, low-cost, and ease of use also for not expertise during both acquisition and processing phase, the SfM-photogrammetry is becoming a valid alternative to the range-based technology for remote sensing and monitoring of dynamic natural environments. The aim of this research was to test and validate the capability of a ground photogrammetric survey to reconstruct a surface by dealing the main practical issues of a ground acquisition and by highlighting the main error sources which may be present within the field data. Furthermore, the feasibility of the SfM-photogrammetry approach for monitoring glacial and periglacial processes was tested in order to highlight the limitation and the potential of the method for these applications. A total of four study sites were surveyed in order to validate the photogrammetric method. A depth investigation on the photo-based approach was carried out in a test field area where different image acquisition, georeferencing methods and processing were compared and evaluated. A terrestrial panorama images acquisition was proposed and tested in this work. This acquisition strategy provided advantages in comparison to a normal single frame acquisition by increasing the spatial coverage of the reconstructed surface and the number of overlapping images that ensure higher accuracy. The potential and limits of the ground-based SfM-photogrammetry approach for monitoring glacial and periglacial processes were investigated in three different environments. For each of these study areas several tests concerning the quality of the obtained photogrammetric digital elevation models (DEMs) were performed. Different resolution and accuracy of the photogrammetric DEMs were obtained for the three case studies according to the different ground survey characteristics and survey object (i.e. extension and accessibility of the areas, camera-object distance, surface coverage, and camera resolution and geometry network). For the investigated areas, the main practical problems of the ground photogrammetric surveys that affected the SfM-photogrammetry results were: i) image quality determined by poor texture (i.e. snow and dark rock area with low contrast) and strong illumination variations during long time photos acquisition, ii) camera network geometry (i.e. high camera-object distance, poor overlapping images) and iii) distribution and accuracy of control measurements. However, the photogrammetric 3D model allowed us to estimate with good accuracy the glacial and periglacial processes respect to the reference data. The investigation on the SfM-photogrammetry quality reconstruction allowed to have a complete view of the critical points and the potential of this method for multitemporal analysis in remote alpine area and thus to assess the applicability range for future realistic case scenarios.L’attività di ricerca sviluppata in questa tesi riguarda lo studio e l’applicazione della fotogrammetria close-range basata sulla tecnica della Structure from Motion o image-based modeling) per la realizzazione di modelli digitali del terreno (DEMs) ad alta risoluzione che costituiscono la base informativa fondamentale per analisi geomorfologiche. Per Structure from Motion (SfM) si intende una tecnica di calcolo che consente di ricostruire tridimensionalmente un oggetto reale da una serie di immagini sovrapposte ricorrendo alle formulazioni proprie della fotogrammetria e agli automatismi (algoritmi) della Computer Vision. La SfM comparata alla tecnologia laser (LiDAR) presenta numerosi vantaggi legati alla elevata portabilità della strumentazione, flessibilità del metodo di ricostruire superfici a diverse scale ad alta risoluzione, il basso costo e la facilità di applicazione, anche da non esperti, sia durante la fase di acquisizione che di elaborazione dei dati. Per tali motivi questa metodologia di rilievo sta diventando una interessante alternativa alla tecnologia LiDAR, in particolare per il rilievo e monitoraggio di ambienti naturali in zone remote. L’obiettivo principale della ricerca è stato quello testare le potenzialità della fotogrammetria terrestre per generare DEMs con accuratezze e precisioni adeguate all’oggetto rilevato e al tipo di analisi, in particolare alle analisi dei processi glaciali e periglaciali. Una indagine approfondita sui principali problemi pratici legati ad un rilievo fotogrammetrico terrestre e sulle principali fonti di errore che caratterizzano il metodo è stata eseguita su un’area di studio. Diversi sono i fattori che influenzano la qualità del modello fotogrammetrico in termini di accuratezza, precisione e risoluzione. Si è dimostrato che la geometria di presa delle immagini e la distribuzione dei punti di controllo necessari per la georeferenziazione sono i fattori chiave che determinano la qualità del modello e possono portare alla formazione di distorsioni se non accuratamente pianificati. Per migliorare la geometria di presa delle immagini è stata testata una diversa strategia di acquisizione basata su immagini panoramiche. Rispetto ad una acquisizione di singole immagine acquisite ad ogni posizione, una acquisizione multi immagine ha generato accuratezze più elevate e una copertura spaziale maggiore dell`area ricostruita. Per validare la tecnica della fotogrammetria terrestre in ambiente glaciale e periglaciale sono stati identificati tre casi studio con diverse caratteristiche in termini di accessibilità, estensione della superficie e tipo di copertura (detrito, neve fresca e roccia). Nello specifico sono stati rilevati con la fotogrammetria terrestre il ghiaccio del Montasio Occidentale, il ghiaccio di La Mare e il rock glacier AVDM3 al fine di calcolare il bilancio di massa annuale dei ghiacciai e le velocità di scorrimento del rock glacier. L’accuratezza del metodo fotogrammetrico è stata convalidata per ogni singolo caso studio con dati LiDAR. Diverse sono le accuratezze e le precisione ottenute nei tre casi studio. Tuttavia, i DEMs generati dalla fotogrammetria hanno permesso di stimare con buona precisione i processi glaciali e periglaciali con accuratezze comprabile con la tecnologia laser. Le indagini effettuate sui vari casi studio hanno permesso di avere una visione completa sul metodo della SfM e sui punti critici e le potenzialità di questo tecnica di rilievo per l'analisi multi-temporale in bacini montani

THE USE OF STRUCTURE FROM MOTION TECHNOLOGIES FOR HIGH-RESOLUTION TERRAIN MODELLING ON HIGH ALTITUDE CATCHMENTS

The research project developed in this Thesis involves the application of close-range photogrammetry based on the Structure from Motion (SfM) approach that allows reconstructing the 3D point cloud of the photographed object from a sequence of overlapping images taken with a common digital camera. Thanks to the characteristics of high portability of the equipment, flexibility of the method to reconstruct surface at different scale with high resolution, low-cost, and ease of use also for not expertise during both acquisition and processing phase, the SfM-photogrammetry is becoming a valid alternative to the range-based technology for remote sensing and monitoring of dynamic natural environments. The aim of this research was to test and validate the capability of a ground photogrammetric survey to reconstruct a surface by dealing the main practical issues of a ground acquisition and by highlighting the main error sources which may be present within the field data. Furthermore, the feasibility of the SfM-photogrammetry approach for monitoring glacial and periglacial processes was tested in order to highlight the limitation and the potential of the method for these applications. A total of four study sites were surveyed in order to validate the photogrammetric method. A depth investigation on the photo-based approach was carried out in a test field area where different image acquisition, georeferencing methods and processing were compared and evaluated. A terrestrial panorama images acquisition was proposed and tested in this work. This acquisition strategy provided advantages in comparison to a normal single frame acquisition by increasing the spatial coverage of the reconstructed surface and the number of overlapping images that ensure higher accuracy. The potential and limits of the ground-based SfM-photogrammetry approach for monitoring glacial and periglacial processes were investigated in three different environments. For each of these study areas several tests concerning the quality of the obtained photogrammetric digital elevation models (DEMs) were performed. Different resolution and accuracy of the photogrammetric DEMs were obtained for the three case studies according to the different ground survey characteristics and survey object (i.e. extension and accessibility of the areas, camera-object distance, surface coverage, and camera resolution and geometry network). For the investigated areas, the main practical problems of the ground photogrammetric surveys that affected the SfM-photogrammetry results were: i) image quality determined by poor texture (i.e. snow and dark rock area with low contrast) and strong illumination variations during long time photos acquisition, ii) camera network geometry (i.e. high camera-object distance, poor overlapping images) and iii) distribution and accuracy of control measurements. However, the photogrammetric 3D model allowed us to estimate with good accuracy the glacial and periglacial processes respect to the reference data. The investigation on the SfM-photogrammetry quality reconstruction allowed to have a complete view of the critical points and the potential of this method for multitemporal analysis in remote alpine area and thus to assess the applicability range for future realistic case scenarios.L’attività di ricerca sviluppata in questa tesi riguarda lo studio e l’applicazione della fotogrammetria close-range basata sulla tecnica della Structure from Motion o image-based modeling) per la realizzazione di modelli digitali del terreno (DEMs) ad alta risoluzione che costituiscono la base informativa fondamentale per analisi geomorfologiche. Per Structure from Motion (SfM) si intende una tecnica di calcolo che consente di ricostruire tridimensionalmente un oggetto reale da una serie di immagini sovrapposte ricorrendo alle formulazioni proprie della fotogrammetria e agli automatismi (algoritmi) della Computer Vision. La SfM comparata alla tecnologia laser (LiDAR) presenta numerosi vantaggi legati alla elevata portabilità della strumentazione, flessibilità del metodo di ricostruire superfici a diverse scale ad alta risoluzione, il basso costo e la facilità di applicazione, anche da non esperti, sia durante la fase di acquisizione che di elaborazione dei dati. Per tali motivi questa metodologia di rilievo sta diventando una interessante alternativa alla tecnologia LiDAR, in particolare per il rilievo e monitoraggio di ambienti naturali in zone remote. L’obiettivo principale della ricerca è stato quello testare le potenzialità della fotogrammetria terrestre per generare DEMs con accuratezze e precisioni adeguate all’oggetto rilevato e al tipo di analisi, in particolare alle analisi dei processi glaciali e periglaciali. Una indagine approfondita sui principali problemi pratici legati ad un rilievo fotogrammetrico terrestre e sulle principali fonti di errore che caratterizzano il metodo è stata eseguita su un’area di studio. Diversi sono i fattori che influenzano la qualità del modello fotogrammetrico in termini di accuratezza, precisione e risoluzione. Si è dimostrato che la geometria di presa delle immagini e la distribuzione dei punti di controllo necessari per la georeferenziazione sono i fattori chiave che determinano la qualità del modello e possono portare alla formazione di distorsioni se non accuratamente pianificati. Per migliorare la geometria di presa delle immagini è stata testata una diversa strategia di acquisizione basata su immagini panoramiche. Rispetto ad una acquisizione di singole immagine acquisite ad ogni posizione, una acquisizione multi immagine ha generato accuratezze più elevate e una copertura spaziale maggiore dell`area ricostruita. Per validare la tecnica della fotogrammetria terrestre in ambiente glaciale e periglaciale sono stati identificati tre casi studio con diverse caratteristiche in termini di accessibilità, estensione della superficie e tipo di copertura (detrito, neve fresca e roccia). Nello specifico sono stati rilevati con la fotogrammetria terrestre il ghiaccio del Montasio Occidentale, il ghiaccio di La Mare e il rock glacier AVDM3 al fine di calcolare il bilancio di massa annuale dei ghiacciai e le velocità di scorrimento del rock glacier. L’accuratezza del metodo fotogrammetrico è stata convalidata per ogni singolo caso studio con dati LiDAR. Diverse sono le accuratezze e le precisione ottenute nei tre casi studio. Tuttavia, i DEMs generati dalla fotogrammetria hanno permesso di stimare con buona precisione i processi glaciali e periglaciali con accuratezze comprabile con la tecnologia laser. Le indagini effettuate sui vari casi studio hanno permesso di avere una visione completa sul metodo della SfM e sui punti critici e le potenzialità di questo tecnica di rilievo per l'analisi multi-temporale in bacini montani

Spherical Photogrammetry as Rescue Documentation for The Reconstruction of some UNESCO Sites in Syria

Ricostruzione per fotogrammetria sferica del minareto abbattuto di Aleppo e delle mura della cittadell

Analysis of sediment yield and delivery using historical digital elevation models

Multitemporal Digital Elevation Models (DEMs) can be used to analyse spatial patterns of erosion and deposition in order to infer and quantify the activity of different geomorphic processes. The photogrammetric analysis of recent and historical imagery, together with present-day surveys using terrestrial and airborne LiDAR or drone-based photogrammetric DEMs, has greatly enhanced opportunities to perform such investigations on a longer temporal scale. We use the example of proglacial areas to highlight these opportunities. In these areas, geomorphic changes following recent glacier retreat have been occurring for a period that can be covered by historical aerial imagery. In the absence of historical quantitative information, investigations of soil, vegetation and also geomorphological (landform) evolution traditionally employed an ergodic approach (space-for-time-substitution): Present-day conditions and dynamics observed at different locations are related to the distance of these locations from the present-day glacier, taking the distance as a substitute for the time since deglaciation. Such an approach relies on a number of assumptions, for example neglecting path-dependence and contingent factors. Multitemporal, historical DEMs (with a sufficient density with respect to the temporal extent of the investigation period) make it possible to observe and quantify morphodynamics on the same areas (e.g., sections of a lateral moraine) for subsequent periods of time. This makes it possible to understand local landform evolution better than by comparative analysis of morphodynamics on different areas for the same period of time. This work presents preliminary results of the SEHAG research unit that sets out to understand the SEnsitivity of High Alpine Geosystems to climate change since the end of the Little Ice Age (c. 1850 AD) in three central Alpine catchments. This project relies on measured and modelled (downscaled reanalysis data) time series of meteorological and hydrological data, and on the photogrammetric analysis of historical aerial and terrestrial photos. By means of an example case study of recently deglaciated steep lateral moraines, we demonstrate two applications of recent and historical DEMs with respect to sediment yield and delivery: (1) Spatially distributed sediment delivery ratios (SDR): We employ a recently published approach to estimating spatially distributed SDR from DEMs of difference (DoD) that represents a data-based (rather than purely model-based) assessment of functional sediment connectivity. This opens the opportunity to investigate the explanatory or predictive capacity of topography-related factors and connectivity indices. For example, we show how the average slope of the contributing area relates to SDR. (2) Scaling of SY: Previous work has found a strong correlation of SY measured in sediment traps (or using accumulated DoD) with the size of the corresponding sediment contributing area (SCA) that can be delineated on a DEM using a set of rules. Multiple historical DEMs offer the opportunity not only to compare time slices with respect to morphodynamics and sediment yield, but also to estimate the parameters of the respective SCA-SY relationships as they change through time. In our case study, SY has increased significantly, with only minor differences in the slope of the SCA-SY relationship