Constantinos Cartalis

Automatic identification of oil spills on satellite images

A fully automated system for the identification of possible oil spills present on Synthetic Aperture Radar (SAR) satellite images based on artificial intelligence fuzzy logic has been developed. Oil spills are recognized by experts as dark patterns of characteristic shape, in particular context. The system analyzes the satellite images and assigns the probability of a dark image shape to be an oil spill. The output consists of several images and tables providing the user with all relevant information for decision-making. The case study area was the Aegean Sea in Greece. The system responded very satisfactorily for all 35 images processed. The complete algorithmic procedure was coded in MS Visual C++ 6.0 in a stand-alone dynamic link library (dll) to be linked with any sort of application under any variant of MS Windows operating system.

Local climate change and urban heat island mitigation techniques – the state of the art

AbstractIncrease of the ambient air temperature in cities caused by the urban heat island phenomenon has a seri- ous impact on the economic and social system of cities. to counterbalance the consequences of the increased urban temperatures important research has been carried out resulting in the development of efficient mitigation technologies. the present paper aims to present the state of the art in terms of local climate change and urban heat island mitigation techniques. In particular, developments in the field on highly reflective materials, cool and green roofs, cool pavements, urban green and of other mitigation technologies are presented in detail, while examples of implemented projects are given.

A surface heat island study of Athens using high-resolution satellite imagery and measurements of the optical and thermal properties of commonly used building and paving materials

High-spatial resolution multispectral satellite images collected over the metropolitan Athens area in Greece were used to generate (a) a shortwave albedo map depicting the albedo spatial variations across the metropolitan area, (b) a fractional vegetation cover map showing the spatial distribution of urban vegetation and (c) a daytime and night-time land surface temperature (LST) map depicting the spatial variations of the surface temperature across the city. From LST maps, cooling and heating regions were identified and analysed to reveal relationships between surface heat islands and urban surface characteristics. Based on the data acquired with the use of satellite images and in order to better define the heat island problem and the mitigation measures that need to be taken, the most common building and paving materials used in the urban fabric of Athens were examined. Their optical properties were measured using a UV/VIS/NIR spectrophotometer fitted with an integrating sphere, an emissometer and their thermal performance was evaluated. Furthermore, measurements of the spectral reflectance help explore the possibility of increasing the near-infrared reflectance of materials in order to increase their total solar reflectance. The solar reflectance index of the samples was calculated in order to characterise them as ‘cool’ or ‘warm’. Cool materials, with high albedo and thermal emittance values, attain lower surface temperatures when exposed to solar radiation, reducing the transference of heat to the environmental air.

Detecting and monitoring plumes caused by major industrial accidents with JPLUME, a new software tool for low-resolution image analysis

A new software tool for the automatic detection and monitoring of plumes caused by major industrial accidents is described. This tool has been designed in order to use near real time information as provided by satellite images, perform sophisticated image analysis and elaborate a user-friendly operational environment for the detection of plumes caused by major industrial accidents. The methodology, based on NOAA/AVHRR (Advanced Very High Resolution Radiometer) imagery, uses a two-dimensional feature space in order to discriminate pixels that contain plumes from those that correspond to clouds or to the underlying surface. The two-dimensional feature space is generated by combining AVHRR channels 1 (visible), 2 (near infrared) and 5 (thermal infrared). The software tool proposed has been coded in JAVA2 language, using the concepts of interoperability and object-oriented programming. This study demonstrates the applicability of the tool for the detection of a plume caused by a massive explosion in a firework factory in Enschede, The Netherlands, on May 13, 2000. The effectiveness and reliability of the software tool was found to be satisfactory, as plume was automatically detected and discriminated from the underlying surface.

Use of Satellite Remote Sensing in Support of Urban Heat Island Studies

Abstract Since the early 1960s, numerous satellite sensors have been launched into orbit to observe and monitor the Earth and its environment. Over the years technologies have significantly improved and satellite missions have increased; more importantly perceptions have changed in terms of the potential and usability of satellite remote sensing. One of the application areas of satellite remote sensing is the study of urban areas. This review provides information about the potential of satellite remote sensing for the study of urban climatology, and in particular the surface urban heat island phenomenon.

Toward resilient cities – a review of definitions, challenges and prospects

This paper provides a review of the definitions, challenges and prospects toward resilient cities. It refers to the definitions provided by several researchers for resilience, links resilience to sustainability, discusses the role of spatial planning in strengthening urban resilience, identifies barriers to resilience, summarizes the requirements for creating resilient cities and exemplifies on cities, climate change and resilience. The paper concludes that the concept of resilience adds a new perspective to the issue of sustainability in the sense that resilience is needed for a sustainable environment. Finally, it refers to the link between climate change adaptation and mitigation plans for cities on the one hand and plans for resilient cities on the other.

Assessing thermal risk in urban areas – an application for the urban agglomeration of Athens

Assessing thermal risk in urban areas, especially in the event of summer heat waves, is essential as it has major implications for human health and influences quality of life in urban areas. Such an assessment is promoted with the use of advanced very high resolution radiometer satellite data and by means of the evaluation of land surface temperature (LST), the estimation of the intensity of surface urban heat island (SUHI) and the variation of the discomfort index (DI), the latter reflecting the most common bioclimatic index used for outdoor thermal comfort applications. Calculations need to provide adequate spatial and temporal depictions of SUHI and DI, as these are correlated with parameters such as land cover/use, urban density, topography, etc. In this study, an assessment of thermal risk is made with the use of satellite data, for the urban agglomeration of Athens in the event of summer heat waves.

The role of quasi-stationary planetary waves in the retrieval of concentrations from satellite measurements

Two recently proposed Reference Atmospheres for the vertical and latitudinal distribution of temperature in the middle atmosphere yield concentration values of nitric oxide (NO) which differ by as much as 25% at high latitudes during winter. The role of the quasi - stationary planetary waves in the temperature distribution at high latitudes during winter is investigated with respect to the above mentioned NO difference. Considering this role, the initial difference is reduced to about 15% maximum.

Integrated fuzzy classification system for automatic oil spill detection using SAR images

Synthetic Aperture Radar (SAR) images are extensively used for the determination of oil slicks in the marine environment, as they are independent of local weather conditions and cloudiness. Oil spills are recognized by the experts eye as dark patterns of characteristic shape in particular context. However, the major difficulty to be dealt with is to differentiate between oil spills and look-alikes of natural origin. A fully automated system for the identification of possible oil spills that imitates the experts choice and decisions has been developed. The systems architecture comprises several distinct modules of supplementary operation (georeferencing, land masking, thresholding, segmentation) and uses their contribution to the analysis and assignment of the probability of a dark image shape to be an oil spill by means of a fuzzy classifier. The output consists of several images and table providing the user with all relevant information as well as supporting decision making. The case study area was the Aegean Sea in Greece. The system responded very satisfactorily for all 35 images processed. The complete procedure described is a fully automated stand-alone application running under Windows operating system.

Estimation of Air Temperatures for the Urban Agglomeration of Athens with the Use of Satellite Data

Changing air temperature trends within urban regions deserve careful monitoring as they may reflect modifications in the thermal environment, including the development of an urban heat island. Air temperature fields need to be dense in order the state of the thermal environment to be adequately assessed; yet in most cases, the networks of ground measuring stations are sparse. This paper attempts to define the relationship between downscaled land surface temperature (LST) at resolution 1 km as deduced from MSG-SEVIRI satellite images, and air temperature (Tair) in the urban agglomeration of Athens, for varying land cover types. Polynomial regression and artificial neural networks are used to estimate Tair from LST at a particular time, whereas the LST values for several hours before are also used. In this way, the “memory” of the surface materials is taken into consideration, practically reflecting the thermal inertia associated with land cover. For urban stations, an average R2 of 0.85 and an RMSE of 1.0-1.2˚C was achieved for the majority of the examined time period, an indication of both the capacity of the methodology to define Tair fields in the area under consideration as well as of the fact that LST is the controlling parameter for Tair. The parametric relations as extracted from the above methodology are in principle applicable for a specific station, as they depend on the land cover and the associated land surface characteristics. They may be also used for stations in areas with similar land cover and in the same climatic zone.