High Resolution Satellite Datasets Research Articles

Capabilities of Satellite-Derived Datasets to Detect Consecutive Indian Monsoon Droughts of 2014 and 2015

India received anomalously deficit southwest monsoon rainfall during 2014 and 2015, which resulted in consecutive droughts across the country. Reliable detection and monitoring of droughts are crucial for the reduction in drought vulnerability and associated socio-economic impacts. In this study, the potential of multiple high-resolution satellite datasets is examined using distinct drought indices over India for these two successive monsoon seasons. The satellite-derived precipitation, soil moisture and land surface temperature estimates are capable of depicting the anomalous drought conditions with some exceptions. A non-parametric multivariate standardized drought index, based on precipitation and soil moisture estimates is proven to be better in the detection of droughts when compared to conventional standardized drought indices. Overall, remote sensing satellite datasets provide immense opportunity to detect and monitor different kinds of droughts using a composite of indices. However, limited temporal records of these high-resolution satellite datasets restrain their applicability from the climatological perspective.

Erratum to: Developing a Collaborative Strategy to Manage and Preserve Cultural Heritage During the Libyan Conflict. The Case of the Gebel Nāfusa

The paper discusses the potential of a collaborative scheme for the development of a protocol for recording and managing the cultural heritage in Libya. The critical political situation in the country urges the development of cultural heritage management policies in order to protect it more thoroughly and consistently. Moving on from the numerous international initiatives and projects dealing with a mostly “remote” approach to the issue, the project here presented to engages with staff members of the Department of Antiquities (DoA) in the development of a joint strategy for the application of remote sensing and geographical information systems (GIS) to the preservation and monitoring of Libyan cultural heritage. A series of training courses resulted in an initial development of new ways of recording and analysing field data for a better awareness of the full range of threats that the archaeology of the country is subject to. Focussing on the case of the Jebel Nafusa, the training involved the assessment of site visibility on satellite imagery, the analysis of high-resolution satellite datasets for archaeological mapping, the creation of a GIS spatial database of field data, and the mapping of risks and threats to archaeology from remote sensing data. This led to the creation of of a risk map showing the areas that are affected by a number of threats, thus giving the DoA a tool to prioritise future fieldwork to keep the assessment of site damage up to date. Only a collaborative approach can lead to a sustainable strategy for the protection of the invaluable cultural heritage of Libya.

Multi-sensor Satellite Pan-sharpening based on IHS and Window Pseudo Wigner Distribution Integrated Approach: Application to WorldView-2 Imagery

ABSTRACTThis paper proposes a new approach to fuse high spatial resolution panchromatic (PAN) image with a low spatial resolution multispectral (MS) image, based on the joint use of intensity-hue-saturation (IHS) and Window Pseudo Wigner Distribution (WPWD), with a motive to reduce the spectral distortion problem of IHS technique. This approach utilises the IHS transform to fuse high-resolution spatial information into the low-resolution MS images, and uses the WPWD to reduce the colour distortion, in the way of generating a new high-resolution PAN image that highly correlates with the intensity image of the IHS transform. The new PAN image is, then, used to replace the intensity image for an inverse IHS transform. The proposed hybrid technique has been compared with the existing hybrid techniques in terms of different fusion rules, computational time, qualitative and different quantitative parameters. The very high resolution satellite dataset, especially, WorldView-2 sensor, which provides data at submeter level has been taken for the pan-sharpening. Analysis of results proved that the concept of proposed IHS and WPWD integration using different fusion rules works well and gives a good trade-off between the enhancement of spatial resolution and preservation of spectral information, along with balanced computational time, when compared to IHS, IHS-DWT, IHS-SWT and IHS-NSCT fusion techniques.

Monitoring olive mills waste disposal areas in Crete using very high resolution satellite data

This paper evaluates the efficiency of different image analysis techniques applied to high resolution multispectral satellite data so as to identify olive oil waste disposal areas in the island of Crete where huge quantities of wastes are produced. For this purpose very high spatial resolution images including Pleiades, SPOT 6, QuickBird, WorldView-2 and GeoEye 1 have been exploited. The research included the application of the Normalised Difference Vegetation Index, Olive Oil Mill Waste Index as well as Principal Component Analysis. Moreover Intensity–Hue–Saturation transformation was carried out. Furthermore, unsupervised classification was performed for a variety of classes (5; 10 and 15) over the same area for two different periods. In addition, supervised linear constrained spectral un-mixing technique has been applied for the WorldView-2 image, to evaluate the potential use of sub-pixel analysis. Indeed, as it is demonstrated NDVI and OOMW indices may be used to enhance the exposure of disposal areas in high resolution satellite datasets, while the application of the PCA and HIS transformations seems to be able to further improve the results. Unsupervised classification techniques, with no ground truth data, can sufficiently work; however temporal changes of the disposal areas can affect the performance of the classifier. The use of spectral library was able to detect OOMW areas with a relatively high rate of success improving the results from the unsupervised classification. Finally, a COSMO-SkyMed radar image has been examined and fused with a hyperspectral EO-ALI image, indicating that such kind of datasets might be also explored for this purpose.

Exploring the Potential of Object Based Image Analysis for Mapping Urban Land Cover

The paper investigates the performance and potential of object based image analysis technique (OBIA) for land cover information extraction from high resolution satellite datasets. Efficiency of the technique has been assessed in different urban land cover situations using merged CARTOSAT-1 and IRS-P6 LISS-IV image subsets of Dehradun, India. Multi-scale iterative Nearest Neighbour classification has been applied. Classification results have been quantitatively evaluated. Results reveal that OBIA is a fast, simple, flexible and efficient semi automated tool to deal with high spatial and spectral heterogeneity inherent in high resolution urban datasets. Integration of shape and texture characteristics with traditional spectral signatures, and use of multiple object levels in the classification process yielded classified map units having high correspondence with real world geographical entities. High accuracies were achieved for spectrally and spatially distinct classes like built up structures and tree covered land. Performance of the technique is impaired in case of classes having overlapping spectral characteristics. The parameters for segmentation and class descriptions developed for one area were successfully transferred to the other with minor adaptations. Utility of the technique is further enhanced by flexibility of visualisation of maps at different levels of classification hierarchy and immediate integration of the classified product in GIS environment with direct realization of vector maps for spatial analysis.

Antarctic summer sea ice concentration and extent: comparison of ODEN 2006 ship observations, satellite passive microwave and NIC sea ice charts

Abstract. Antarctic sea ice cover has shown a slight increase (<1%/decade) in overall observed ice extent as derived from satellite mapping from 1979 to 2008, contrary to the decline observed in the Arctic regions. Spatial and temporal variations of the Antarctic sea ice however remain a significant problem to monitor and understand, primarily due to the vastness and remoteness of the region. While satellite remote sensing has provided and has great future potential to monitor the variations and changes of sea ice, uncertainties remain unresolved. In this study, the National Ice Center (NIC) ice edge and the AMSR-E (Advanced Microwave Scanning Radiometer-Earth Observing System) ice extent are examined, while the ASPeCt (Antarctic Sea Ice Process and Climate) ship observations from the Oden expedition in December 2006 are used as ground truth to verify the two products during Antarctic summer. While there is a general linear trend between ASPeCt and AMSR-E ice concentration estimates, there is poor correlation (R2=0.41) and AMSR-E tends to underestimate the low ice concentrations. We also found that the NIC sea ice edge agrees well with ship observations, while the AMSR-E shows the ice edge further south, consistent with its poorer detection of low ice concentrations. The northward extent of the ice edge at the time of observation (NIC) had mean values varying from 38 km to 102 km greater on different days for the area as compared with the AMSR-E sea ice extent. For the circumpolar area as a whole in the December period examined, AMSR-E therefore may underestimate the area inside the ice edge at this time by up to 14% or, 1.5 million km2 less area, compared to the NIC ice charts. Preliminary comparison of satellite scatterometer data however, suggests better resolution of low concentrations than passive microwave, and therefore better agreement with ship observations and NIC charts of the area inside the ice edge during Antarctic summer. A reanalysis data set for Antarctic sea ice extent that relies on the decade long scatterometer and high resolution satellite data set, instead of passive microwave, may therefore give better fidelity for the recent sea ice climatology.

Thermal Stress and Coral Cover as Drivers of Coral Disease Outbreaks

Very little is known about how environmental changes such as increasing temperature affect disease dynamics in the ocean, especially at large spatial scales. We asked whether the frequency of warm temperature anomalies is positively related to the frequency of coral disease across 1,500 km of Australia's Great Barrier Reef. We used a new high-resolution satellite dataset of ocean temperature and 6 y of coral disease and coral cover data from annual surveys of 48 reefs to answer this question. We found a highly significant relationship between the frequencies of warm temperature anomalies and of white syndrome, an emergent disease, or potentially, a group of diseases, of Pacific reef-building corals. The effect of temperature was highly dependent on coral cover because white syndrome outbreaks followed warm years, but only on high (>50%) cover reefs, suggesting an important role of host density as a threshold for outbreaks. Our results indicate that the frequency of temperature anomalies, which is predicted to increase in most tropical oceans, can increase the susceptibility of corals to disease, leading to outbreaks where corals are abundant.