Fusion of High Resolution Multispectral Imagery in Vulnerable Coastal and Land Ecosystems

Ecosystems provide a wide variety of useful resources that enhance human welfare, but these resources are declining due to climate change and anthropogenic pressure. In this work, three vulnerable ecosystems, including shrublands, coastal areas with dunes systems and areas of shallow water, are studied. As far as these resources’ reduction is concerned, remote sensing and image processing techniques could contribute to the management of these natural resources in a practical and cost-effective way, although some improvements are needed for obtaining a higher quality of the information available. An important quality improvement is the fusion at the pixel level. Hence, the objective of this work is to assess which pansharpening technique provides the best fused image for the different types of ecosystems. After a preliminary evaluation of twelve classic and novel fusion algorithms, a total of four pansharpening algorithms was analyzed using six quality indices. The quality assessment was implemented not only for the whole set of multispectral bands, but also for the subset of spectral bands covered by the wavelength range of the panchromatic image and outside of it. A better quality result is observed in the fused image using only the bands covered by the panchromatic band range. It is important to highlight the use of these techniques not only in land and urban areas, but a novel analysis in areas of shallow water ecosystems. Although the algorithms do not show a high difference in land and coastal areas, coastal ecosystems require simpler algorithms, such as fast intensity hue saturation, whereas more heterogeneous ecosystems need advanced algorithms, as weighted wavelet ‘à trous’ through fractal dimension maps for shrublands and mixed ecosystems. Moreover, quality map analysis was carried out in order to study the fusion result in each band at the local level. Finally, to demonstrate the performance of these pansharpening techniques, advanced Object-Based (OBIA) support vector machine classification was applied, and a thematic map for the shrubland ecosystem was obtained, which corroborates wavelet ‘à trous’ through fractal dimension maps as the best fusion algorithm for this ecosystem

Assessment of Component Selection Strategies in Hyperspectral Imagery

Hyperspectral imagery (HSI) integrates many continuous and narrow bands that cover different regions of the electromagnetic spectrum. However, the main challenge is the high dimensionality of HSI data due to the ’Hughes’ phenomenon. Thus, dimensionality reduction is necessary before applying classification algorithms to obtain accurate thematic maps. We focus the study on the following feature-extraction algorithms: Principal Component Analysis (PCA), Minimum Noise Fraction (MNF), and Independent Component Analysis (ICA). After a literature survey, we have observed a lack of a comparative study on these techniques as well as accurate strategies to determine the number of components. Hence, the first objective was to compare traditional dimensionality reduction techniques (PCA, MNF, and ICA) in HSI of the Compact Airborne Spectrographic Imager (CASI) sensor and to evaluate different strategies for selecting the most suitable number of components in the transformed space. The second objective was to determine a new dimensionality reduction approach by dividing the CASI HSI regarding the spectral regions covering the electromagnetic spectrum. The components selected from the transformed space of the different spectral regions were stacked. This stacked transformed space was evaluated to see if the proposed approach improves the final classification

Influence of Pansharpening in Obtaining Accurate Vegetation Maps

In recent decades, there has been a decline in ecosystem services. Thus, the development of reliable methodologies to monitor ecosystems is becoming important. In this context, the availability of very high resolution sensors offer practical and cost-effective means for good environmental management. However, improvements in the data received are becoming necessary to obtain higher quality information in order to get reliable thematic maps. One improvement is pansharpening, which enhances the spatial resolution of the multispectral bands by incorporating information from a panchromatic image. The main goal of this work was to assess the influence of pansharpening techniques in obtaining precise vegetation maps. Thus, pixel- and object-based classification techniques were implemented and applied to fused imagery using different pansharpening algorithms. Worldview-2 high resolution imagery was used due to its excellent spatial and spectral characteristics. The Teide National Park, in The Canary Islands (Spain), was chosen as the study area since it is a vulnerable heterogeneous ecosystem. The vegetation classes of interest considered were established by the National Park conservation managers. Weighted Wavelet ‘à trous’ through Fractal Dimension Maps pansharpening algorithm demonstrated a superior performance in the image fusion preprocessing step, while the most appropriate classifier to generate accurate vegetation thematic maps in heterogenic and mixed ecosystems was the Bayes method after the segmentation stage, even though Support Vector Machine achieved the highest overall accuracy

Multisensor fusion for the accurate classification of vegetation in complex ecosystems

The use of geospatial tools to monitor natural ecosystems is a fundamental task to preserve the environment. In this context, remote sensing data can provide a valuable source of information to complement field observations, offering frequent and accurate imagery to support the mapping and monitoring of natural areas. The growing availability of hyperspectral (HS) data can provide a valuable solution but the spectral richness provided by hyperspectral sensors is usually at the expense of spatial resolution. To alleviate this inconvenience, instead of satellite platforms, airborne sensors can be considered. In this work, the accurate mapping of a complex shrubland ecosystem has been accomplished using multisensor imagery. Specifically, airborne CASI data (68 bands and 75 cm of pixel size) has been fused with an orthophoto (25 cm) to increase the spatial detail. A comprehensive analysis of 11 sharpening algorithms has been performed and, to improve the Support Vector Machine (SVM) classification accuracy, different input features have been considered. Excellent results have been achieved and the importance to improve the spatial resolution has been demonstrated

Hyperspectral Classification Through Unmixing Abundance Maps Addressing Spectral Variability

International audienc

Assessment of Hyperspectral Sharpening Methods for the Monitoring of Natural Areas Using Multiplatform Remote Sensing Imagery

International audienc

Classification Using Unmixing Models in Areas With Substantial Endmember Variability

International audienc

Extended Linear Mixing Model in an Ecosytem with High Spectral Variability

International audienc