Machine learning classification and accuracy assessment from high-resolution images of coastal wetlands

High-resolution images obtained by multispectral cameras mounted on Unmanned Aerial Vehicles (UAVs) are helping to capture the heterogeneity of the environment in images that can be discretized in categories during a classification process. Currently, there is an increasing use of supervised machine learning (ML) classifiers to retrieve accurate results using scarce datasets with samples with non-linear relationships. We compared the accuracies of two ML classifiers using a pixel and object analysis approach in six coastal wetland sites. The results show that the Random Forest (RF) performs better than K-Nearest Neighbors (KNN) algorithm in the classification of pixels and objects and the classification based on pixel analysis is slightly better than the object-based analysis. The agreement between the classifications of objects and pixels is higher in Random Forest. This is likely due to the heterogeneity of the study areas, where pixel-based classifications are most appropriate. In addition, from an ecological perspective, as these wetlands are heterogeneous, the pixel-based classification reflects a more realistic interpretation of plant community distribution

Optimizing the scale of observation for intertidal habitat classification through multiscale analysis

Monitoring intertidal habitats, such as oyster reefs, salt marshes, and mudflats, is logistically challenging and often cost- and time-intensive. Remote sensing platforms, such as unoccupied aircraft systems (UASs), present an alternative to traditional approaches that can quickly and inexpensively monitor coastal areas. Despite the advantages offered by remote sensing systems, challenges remain concerning the best practices to collect imagery to study these ecosystems. One such challenge is the range of spatial resolutions for imagery that is best suited for intertidal habitat monitoring. Very fine imagery requires more collection and processing times. However, coarser imagery may not capture the fine-scale patterns necessary to understand relevant ecological processes. This study took UAS imagery captured along the Gulf of Mexico coastline in Florida, USA, and resampled the derived orthomosaic and digital surface model to resolutions ranging from 3 to 31 cm, which correspond to the spatial resolutions achievable by other means (e.g., aerial photography and certain commercial satellites). A geographic object-based image analysis (GEOBIA) workflow was then applied to datasets at each resolution to classify mudflats, salt marshes, oyster reefs, and water. The GEOBIA process was conducted within R, making the workflow open-source. Classification accuracies were largely consistent across the resolutions, with overall accuracies ranging from 78% to 82%. The results indicate that for habitat mapping applications, very fine resolutions may not provide information that increases the discriminative power of the classification algorithm. Multiscale classifications were also conducted and produced higher accuracies than single-scale workflows, as well as a measure of uncertainty between classifications

MultiscaleDTM : an open‐source R package for multiscale geomorphometric analysis

Digital terrain models (DTMs) are datasets containing altitude values above or below a reference level, such as a reference ellipsoid or a tidal datum over geographic space, often in the form of a regularly gridded raster. They can be used to calculate terrain attributes that describe the shape and characteristics of topographic surfaces. Calculating these terrain attributes often requires multiple software packages that can be expensive and specialized. We have created a free, open‐source R package, MultiscaleDTM , that allows for the calculation of members from each of the five major thematic groups of terrain attributes: slope, aspect, curvature, relative position, and roughness, from a regularly gridded DTM. Furthermore, these attributes can be calculated at multiple spatial scales of analysis, a key feature that is missing from many other packages. Here, we demonstrate the functionality of the package and provide a simulation exploring the relationship between slope and roughness. When roughness measures do not account for slope, these attributes exhibit a strong positive correlation. To minimize this correlation, we propose a new roughness measure called adjusted standard deviation. In most scenarios tested, this measure produced the lowest rank correlation with slope out of all the roughness measures tested. Lastly, the simulation shows that some existing roughness measures from the literature that are supposed to be independent of slope can actually exhibit a strong inverse relationship with the slope in some cases

Detecção semiautomática de árvores em pomar de mangueira irrigada a partir de imagens obtidas por drone.

O monitoramento da população de plantas em áreas agrícolas é fundamental para acompanhar a produtividade, auxiliar no planejamento e na tomada de decisão. Assim, objetivou-se propor um protocolo para identificação remota de árvores de mangueiras no Submédio do Vale do São Francisco por meio de softwarese pluginsgratuitosaplicados em imagens aéreas obtidas com drones. O estudo foi desenvolvido em três pomares de mangueira, empregando-semodelos digitais obtidos a partir de ortomosaicos gerados em três qualidades de processamento; avaliados no QGIS utilizando-se os plugins‘Tree Density Calculator’ e ‘SAGA GIS’. Os resultados obtidos foram avaliados por meio dos índices de Precisão, Revocação e F1–Score. O índice de Precisão foi mais elevado para o processamento em qualidade baixa. Oíndice de Revocação apresentou maiores valores no processamento em qualidade média e elevada, indicando que quanto maior a qualidade do processamento, maior éa chance de acertar na contagem de árvores.Os maiores valores de F1–Scoreforam observados para o Tree DensityCalculatorcom processamento na resolução baixa. Recomenda-se o uso de um protocolo para a identificação e contagem remota de árvores de mangueiras, de forma semiautomática por meio da utilização de imagens obtidas por VANTse softwaresde código livre e aberto

Deep Learning Methods for Remote Sensing

Remote sensing is a field where important physical characteristics of an area are exacted using emitted radiation generally captured by satellite cameras, sensors onboard aerial vehicles, etc. Captured data help researchers develop solutions to sense and detect various characteristics such as forest fires, flooding, changes in urban areas, crop diseases, soil moisture, etc. The recent impressive progress in artificial intelligence (AI) and deep learning has sparked innovations in technologies, algorithms, and approaches and led to results that were unachievable until recently in multiple areas, among them remote sensing. This book consists of sixteen peer-reviewed papers covering new advances in the use of AI for remote sensing

Hildesheimer Geographische Studien, Band 9

In diesem Band enthalten: S. 1 – 34 Eika Ehme & Sabine Panzer-Krause Image und Stadtteilentwicklung: Attraktivierung innenstadtnaher Wohnviertel für Studierende und identitätsstiftende Maßnahmen am Beispiel der Hildesheimer Neustadt S. 35 – 65 Michelle Kieselstein Niedersächsische Lehrpfade – wie können traditionelle Bildungsinstrumente eine Bildung für nachhaltige Entwicklung ermöglichen? S. 66 – 90 Mischa Wittmar & Martin Sauerwein Geoökologische Untersuchungen zur Immissionsbelastung des Stadtwaldes Eilenriede (Hannover) S. 91 – 123 Moritz Sandner, Robin Stadtmann & Martin Sauerwein Möglichkeiten und Grenzen offener Fernerkundungsdaten und Open-Source- Software zur Landbedeckungsklassifikation des Nationalparks Cinque Terre (Italien) S. 124 – 129 Informationen aus dem Institut 2017 – 201

SegOptim—A new R package for optimizing object-based image analyses of high-spatial resolution remotely-sensed data

Geographic Object-based Image Analysis (GEOBIA) is increasingly used to process high-spatial resolution imagery, with applications ranging from single species detection to habitat and land cover mapping. Image segmentation plays a key role in GEOBIA workflows, allowing to partition images into homogenous and mutually exclusive regions. Nonetheless, segmentation techniques require a robust parameterization to achieve the best results. Frequently, inappropriate parameterization leads to sub-optimal results and difficulties in comparing distinct methods. Here, we present an approach based on Genetic Algorithms (GA) to optimize image segmentation parameters by using the performance scores from object-based classification, thus allowing to assess the adequacy of a segmented image in relation to the classification problem. This approach was implemented in a new R package called SegOptim, in which several segmentation algorithms are interfaced, mostly from open-source software (GRASS GIS, Orfeo Toolbox, RSGISLib, SAGA GIS, TerraLib), but also from proprietary software (ESRI ArcGIS). SegOptim also provides access to several machine-learning classification algorithms currently available in R, including Gradient Boosted Modelling, Support Vector Machines, and Random Forest. We tested our approach using very-high to high spatial resolution images collected from an Unmanned Aerial Vehicle (0.03 – 0.10 m), WorldView-2 (2 m), RapidEye (5 m) and Sentinel-2 (10 – 20 m) in six different test sites located in northern Portugal with varying environmental conditions and for different purposes, including invasive species detection and land cover mapping. The results highlight the added value of our novel comparison of image segmentation and classification algorithms. Overall classification performances (assessed through cross-validation with the Kappa index) ranged from 0.85 to 1.00. Pilot-tests show that our GA-based approach is capable of providing sound results for optimizing the parameters of different segmentation algorithms, with benefits for classification accuracy and for comparison across techniques. We also verified that no particular combination of an image segmentation and a classification algorithm is suited for all the tasks/objectives. Consequently, it is crucial to compare and optimize available methods to understand which one is more suited for a certain objective. Our approach allows a closer integration between the segmentation and classification stages, which is of high importance for GEOBIA workflows. The results from our tests confirm that this integration has benefits for comparing and optimizing both processes. We discuss some limitations of the SegOptim approach (and potential solutions) as well as a future roadmap to expand its current functionalities.</p