Showing papers by "Academy of Finland published in 2019"

Is field-measured tree height as reliable as believed – A comparison study of tree height estimates from field measurement, airborne laser scanning and terrestrial laser scanning in a boreal forest

Abstract: Quantitative comparisons of tree height observations from different sources are scarce due to the difficulties in effective sampling. In this study, the reliability and robustness of tree height observations obtained via a conventional field inventory, airborne laser scanning (ALS) and terrestrial laser scanning (TLS) were investigated. A carefully designed non-destructive experiment was conducted that included 1174 individual trees in 18 sample plots (32 m × 32 m) in a Scandinavian boreal forest. The point density of the ALS data was approximately 450 points/m2. The TLS data were acquired with multi-scans from the center and the four quadrant directions of the sample plots. Both the ALS and TLS data represented the cutting edge point cloud products. Tree heights were manually measured from the ALS and TLS point clouds with the aid of existing tree maps. Therefore, the evaluation results revealed the capacities of the applied laser scanning (LS) data while excluding the influence of data processing approach such as the individual tree detection. The reliability and robustness of different tree height sources were evaluated through a cross-comparison of the ALS-, TLS-, and field- based tree heights. Compared to ALS and TLS, field measurements were more sensitive to stand complexity, crown classes, and species. Overall, field measurements tend to overestimate height of tall trees, especially tall trees in codominant crown class. In dense stands, high uncertainties also exist in the field measured heights for small trees in intermediate and suppressed crown class. The ALS-based tree height estimates were robust across all stand conditions. The taller the tree, the more reliable was the ALS-based tree height. The highest uncertainty in ALS-based tree heights came from trees in intermediate crown class, due to the difficulty of identifying treetops. When using TLS, reliable tree heights can be expected for trees lower than 15–20 m in height, depending on the complexity of forest stands. The advantage of LS systems was the robustness of the geometric accuracy of the data. The greatest challenges of the LS techniques in measuring individual tree heights lie in the occlusion effects, which lead to omissions of trees in intermediate and suppressed crown classes in ALS data and incomplete crowns of tall trees in TLS data.

Semantic segmentation of road furniture in mobile laser scanning data

Abstract: Road furniture recognition has become a prevalent issue in the past few years because of its great importance in smart cities and autonomous driving. Previous research has especially focussed on pole-like road furniture, such as traffic signs and lamp posts. Published methods have mainly classified road furniture as individual objects. However, most road furniture consists of a combination of classes, such as a traffic sign mounted on a street light pole. To tackle this problem, we propose a framework to interpret road furniture at a more detailed level. Instead of being interpreted as single objects, mobile laser scanning data of road furniture is decomposed in elements individually labelled as poles, and objects attached to them, such as, street lights, traffic signs and traffic lights. In our framework, we first detect road furniture from unorganised mobile laser scanning point clouds. Then detected road furniture is decomposed into poles and attachments (e.g. traffic signs). In the interpretation stage, we extract a set of features to classify the attachments by utilising a knowledge-driven method and four representative types of machine learning classifiers, which are random forest, support vector machine, Gaussian mixture model and naive Bayes, to explore the optimal method. The designed features are the unary features of attachments and the spatial relations between poles and their attachments. Two experimental test sites in Enschede dataset and Saunalahti dataset were applied, and Saunalahti dataset was collected in two different epochs. In the experimental results, the random forest classifier outperforms the other methods, and the overall accuracy acquired is higher than 80% in Enschede test site and higher than 90% in both Saunalahti epochs. The designed features play an important role in the interpretation of road furniture. The results of two epochs in the same area prove the high reliability of our framework and demonstrate that our method achieves good transferability with an accuracy over 90% through employing the training data of one epoch to test the data in another epoch.

Introduction: Hagiography and Lived Religion

Abstract: Present in both everyday life and festive rituals, saints—both officially canonized and unofficially venerated—provide a prime example of lived religion in early modern Catholicism. To early modern Catholics, religious experience was a dynamic interaction between believers, God and the saints. In this chapter, we argue that the study of lived religion, understood as individual and communal participation in religious rituals, performances and other practices, allows us to gain new insights into the experiences and expressions of early modern religiosity, without lapsing into simplifying dichotomies or essentialist interpretations of the past. Rather, the concept of lived religion helps us link individual or communal experience to a larger societal framework. Considering the dramatic rise in hagiographic material in the wake of the Catholic Reformation and its reinforcement of the cult of saints, and supported by the invention of the printing press, we further propose that hagiographic material is ideally suited for the study of lived religious experience both on an individual and communal level. By hagiography, we refer to a multitude of material related to saints’ cults and canonisations, such as vitae (or saints’ lives), spiritual biographies, miracle narratives, canonisation processes, iconography, and drama. It is outright perplexing, how little use early modern scholars have, in comparison to medievalists, hitherto made of this abundant genre. Taking into account the changes and continuities in canonization procedures and their interaction with hagiographic material, the chapter introduces a sample of case studies from the fifteenth to the seventeenth century that illustrate how the veneration of saints helped early modern Catholics to give meaning and shape to their various mundane and religious experiences.

Saintly Shepherdesses: Semi-religious Women and Identity Formation in Seventeenth-Century France

Abstract: The identity training of the members of the Daughters of Charity, a Catholic community, or Company, of religious laywomen, is the subject of Rose-Marie Peake’s article ‘Saintly Shepherdesses: Semi-religious Women and Identity Formation in Seventeenth-century France.’ She examines the ways hagiography of shepherdesses was used to mould the behaviour and appearance of the sisters. Peake argues that an overall rustic discourse, composed importantly by the aforementioned hagiography, served the survival of the Company and warded off monastic enclosure, which would have endangered the sisters’ apostolic mission among the underprivileged.

Cure, Community, and the Miraculous in Early Modern Florence

Abstract: The social history of medicine is in the focus in Jenni Kuuliala’s article ‘Cure, Community, and the Miraculous in Early Modern Florence’. She discusses the interplay of lived medicine and lived religion in late sixteenth-century Florence based on the apostolic canonisation inquiry of St Andrea Corsini, held in Florence in 1606. Through testimonies about the healing miracles St Andrea performed, Kuuliala analyses the role the community had in the search for different medical and religious healing methods, and how medicine and religion collaborated and complemented each other in this time period.

Modelling 3D magnetic networks in a realistic solar atmosphere

Abstract: The magnetic network extending from the photosphere (solar radius \simeq R_\odot) to lower corona (R_\odot + 10 Mm) plays an important role in the heating mechanisms of the solar atmosphere. Here we further develop the models with realistic open magnetic flux tubes of Gent et al. (2013, 2014) in order to model more complicated configurations. Closed magnetic loops, and combinations of closed and open magnetic flux tubes are modelled. These are embedded within a realistic stratified atmosphere, subject to solar gravity and including the Interface Region. Constructing a magnetic field comprising self-similar magnetic flux tubes, an analytic solution for the kinetic pressure and plasma density is derived following Gent et al. (2014). Combining flux tubes of opposite polarity it is possible to create a steady background magnetic field configuration modelling realistic solar atmosphere. The result can be applied to SOHO/MDI and SDO/HMI and other magnetograms from the solar surface, upon which realistic photospheric motions can be simulated to explore the mechanism of energy transport. We demonstrate this powerful and versatile method with an application to Helioseismic and Magnetic Imager data.