Panagiotis Partsinevelos

Statistical Models and Latest Results in the Determination of the Absolute Bias for the Radar Altimeters of Jason Satellites using the Gavdos Facility

The dedicated calibration site for satellite radar altimeters in Gavdos, Greece, has been operational as of 2004. The island of Gavdos is located along a repeating ground track of Jason satellites, adjacent to Envisat, where the altimeter and radiometer do not experience significant land intrusion. In this article, the models and techniques for calculating the satellite altimeter bias, as well as the software tool called “TUCalibrit,” are presented. In summary, over cycles 209–259 for Jason-1 and cycles 1–40 for Jason-2, the altimeter biases have been estimated as B(J1) = +103.6 mm ± 4.7 mm and B(J2) = +181.9 mm ± 6.7 mm, respectively.

Change detection of surface mining activity and reclamation based on a machine learning approach of multi-temporal Landsat TM imagery

Being able to quantify land cover changes due to mining and reclamation at a watershed scale is of critical importance in managing and assessing their potential impacts to the Earth system. In this study, a remote sensing-based methodology is proposed for quantifying the impact of surface mining activity and reclamation from a watershed to local scale. The method is based on a Support Vector Machines (SVMs) classifier combined with multi-temporal change detection of Landsat TM imagery. The performance of the technique was evaluated at selected open mining sites located in the island of Milos in Greece. Assessment of the mining impact in the studied areas was based on the confusion matrix statistics, supported by co-orbital QuickBird-2 very high spatial resolution imagery. Overall classification accuracy of the thematic land cover maps produced was reported over 90%. Our analysis showed expansion of mining activity throughout the whole 23-year study period, while the transition of mining areas to soil and vegetation was evident in varying rates. Our results evidenced the ability of the method under investigation in deriving highly and accurate land cover change maps, able to identify the mining areas as well as those in which excavation was replaced by natural vegetation. All in all, the proposed technique showed considerable promise towards the support of a sustainable environmental development and prudent resource management.

Ascending and Descending Passes for the Determination of the Altimeter Bias of Jason Satellites using the Gavdos Facility

This paper presents the improvements made on the calibration methodology conducted at the Gavdos calibration/validation facility along with the latest altimeter calibration results for Jason-1 and Jason-2 satellite missions. Calibration results are presented, for the first time, for both ascending and descending passes of Jason satellites. The altimeter bias for Jason-2 has been estimated to be +173 ± 4 mm for Pass No. 109 and +171 ± 5 mm for Pass No. 018 over cycles 1–79. In tandem mission, the difference between Jason-1 and Jason-2 has been determined to be 72mm (Pass No. 109) and 68 mm (pass No. 018) and over cycles 2–20.

Microplastics Generation: Onset of Fragmentation of Polyethylene Films in Marine Environment Mesocosms

The fragmentation of high-density polyethylene (HDPE) films from single-use supermarket plastic bags to microplastics under laboratory-simulated onshore and nearshore conditions was investigated for a period of 6 months. The weathering process of the plastic strips either on beach sand or in seawater under direct natural sunlight was monitored by tensile strength, molecular weight measurements, FTIR, weight loss and image processing of photographs of the plastic strips before and after mild mechanical stress was applied. The latter represents a novel method proposed for determining the onset of fragmentation through the application of mild mechanical stress on the weathered plastic samples emulating the action of sand and wind on a beach. It was found that 12 h of application of mild mechanical stress in rotating glass bottles filled partially with sand was sufficient time to reach the maximum degree of fragmentation that could occur for the weathered plastics samples being tested. For example, applied mechanical stress yielded an area loss of almost 14% for samples weathered for a period of 5 months and about 16.7% after 5.5 months. While tensile strength tests and molecular weight measurements were rather inconclusive till the very last month when the onset of fragmentation was identified; FTIR measurements revealed that samples under ultraviolet irradiation were gradually modified chemically until fragmentation commenced. After 6 months of weathering, molecular weight measurements showed a 60% reduction for sample SMB-1 whereas for sample SMB-2 the measurement was not possible due to extensive fragmentation. The onset of fragmentation for SMB-1 and SMB-2 samples occurred at a cumulative luminance of 5.3x106 lux•d and in the presence of atmospheric oxygen whereby the polymer films broke down partially to microplastics. When the UV exposure reached 7.2x106 lux•d the weathered plastic strips broke down fully to microplastics with the application of a mild mechanical stress. Samples placed in seawater proved to be resistant to fragmentation compared to those on sand over the six-month period of the weathering experiment. The direct implication of this work is that beached macroplastic debris should be regularly collected from the seashore before they are weathered by sunlight and returned to the

Terrain segmentation of Egypt from multi-temporal night LST imagery and elevation data.

Abstract: Monthly night averaged land surface temperature (LST) MODIS imagery was analyzed throughout a year-period (2006), in an attempt to segment the terrain of Egypt into regions with different LST seasonal variability, and represent them parametrically. Regions with distinct spatial and temporal LST patterns were outlined using several clustering techniques capturing aspects of spatial, temporal and temperature homogeneity or differentiation. Segmentation was supplemented, taking into consideration elevation, morphological features and landcover information. The northern coastal region along the Mediterranean Sea occupied by lowland plain areas corresponds to the coolest clusters indicating a latitude/elevation dependency of seasonal LST variability. On the other hand, for the inland regions, elevation and terrain dissection plays a key role in LST seasonal variability, while an east to west variability of clusters’ spatial distribution is evident. Finally, elevation biased clustering revealed annual LST differences among the regions with the same physiographic/terrain characteristics. Thermal terrain segmentation outlined the temporal variation of LST during 2006, as well as the spatial distribution of LST zones.

The optimal location of the distribution point of the belt conveyor system in continuous surface mining operations

Continuous surface mining projects are dynamic and quite complex. They are characterized by geological and spatial variability and several stochastic parameters that affect initial planning and final design. In strategic mine planning and operations management of such projects, the location of the distribution point of the belt conveyor system (BCDP) is of high importance as it directly influences mine development and the production schedule. In addition, the spatial location of the BCDP directly affects project cash flow including investment and operating costs and, as a result, the economic viability of the mining project. Therefore, the problem of the optimal location of BCDP could be defined as an economic optimization problem focusing on the material transportation cost. In this paper a model for the optimal location of BCDP in continuous surface mines is formulated based on the minimization of the transportation cost within the lifetime of the mine. A computer model was developed based on a methodological approach and was verified utilizing an actual lignite deposit which was simplified in terms of geometry and geology. Simulation results compare well with actual data available for the specific lignite mine.

Towards Autonomous Modular UAV Missions: The Detection, Geo-Location and Landing Paradigm

Nowadays, various unmanned aerial vehicle (UAV) applications become increasingly demanding since they require real-time, autonomous and intelligent functions. Towards this end, in the present study, a fully autonomous UAV scenario is implemented, including the tasks of area scanning, target recognition, geo-location, monitoring, following and finally landing on a high speed moving platform. The underlying methodology includes AprilTag target identification through Graphics Processing Unit (GPU) parallelized processing, image processing and several optimized locations and approach algorithms employing gimbal movement, Global Navigation Satellite System (GNSS) readings and UAV navigation. For the experimentation, a commercial and a custom made quad-copter prototype were used, portraying a high and a low-computational embedded platform alternative. Among the successful targeting and follow procedures, it is shown that the landing approach can be successfully performed even under high platform speeds.

Dronesourcing: a modular, expandable multi-sensor UAV platform for combined, real-time environmental monitoring

ABSTRACT The systematic environmental monitoring of the land, atmosphere, oceans and their coupling zones, is assisted by the use of unmanned aerial vehicles (UAVs) that can operate over rural and/or urban areas to provide enhanced spatial and temporal measurement resolutions compared against corresponding satellite products. The international UAV market includes a vast number of solutions that carry sensors for environmental monitoring varying in type, flight time, carrying weight, communication, and autonomous flight. The majority of these commercial UAVs (especially the low-cost ones) have been designed for specific applications and their main disadvantage is that they can only integrate the payload they have been initially designed to carry, thus presenting minimal modularity. This work presents a modular and affordable platform where the user can easily adapt almost any type of environmental monitoring sensor, which can transmit its measurements to the UAV flight controller without the need for any additional modification. A novel communication protocol has been developed that is also capable to incorporate proximity sensors for collision avoidance. In addition, a wireless mobile telecommunications module incorporation through the use of mobile devices on the UAV provides real-time animated map generation along with cooperative capabilities for fleet missions.

Detection of small-scale rockfall incidents using their seismic signature

Several algorithms have been effectively used to identify the seismic signature of rockfall incidents, which constitute a significant threat for human lives and infrastructure especially when occurring along transportation networks. These algorithms have been mostly evaluated using data from large scale rockfall events that release a large amount of energy. However, low-energy rockfall events (< 100 Joules) triggered by small-sized individual rocks falling from small heights can be severely destructive. In this study, a three-parameter algorithm has been developed to identify low-energy rockfall events. An experimental setup was implemented to 1) validate the results obtained by this algorithm against visual inspection of seismic signals records, 2) define the optimal algorithm parameterization to minimize false alarms, and 3) investigate whether tri-axial vibration monitoring can be replaced by a uniaxial device in order to reduce the installation cost of a real-time rockfall monitoring system. It was found that the success rate of the proposed algorithm exceeds 80%independently of the parameters used, while event identification at a maximum distance with minimal false alarms was achieved when using mean± 3σ as the threshold criterion and 6 ms and 4 ms as the trigger and event window parameters respectively. Finally, it was found that for the specific experimental setup, a uniaxial device could be used for rockfall event identification.

Ship extraction and categorization from ASTER VNIR imagery

We present a methodology for ship extraction and categorization from relatively low resolution multispectral ASTER imagery, corresponding to the sea region south east of Athens in Greece. At a first level, in the radiometrically corrected image, quad tree decomposition and bounding rectangular extraction automatically outline location of objects - possible ships, by statistically evaluating spectral responses throughout the segmented image. Subsequently, the object borders within the rectangular regions are extracted, while connected component labelling combined by size and shape filtering allows ship characterization. The ships’ spectral signature is determined in green, red and infrared bands while cluster analysis allows the identification of ship categories on the basis of their size and reflectance. Additional pixel- based measures reveal estimated ship orientation, direction, movement, stability and turning. The results are complemented with additional geographic information and inference tools are formed towards the determination of probable ship type and its destination.