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Complex Environment Noise Barrage Jamming Eeffects on Airborne Warning Radar
Issue:
Volume 6, Issue 2, December 2018
Pages:
59-63
Received:
13 June 2018
Accepted:
9 July 2018
Published:
8 August 2018
Abstract: Modern warfare is carried out in a complex electromagnetic environment, where noise suppression interference directly affects the detection ability of airborne warning radar to target, in order to make airborne warning radar play its due role in battlefield. More and more requirements are put forward for radar combat capability in complex electromagnetic environment, that is, the requirement of radar anti-jamming ability in complex electromagnetic environment is becoming higher and higher. Suppression jamming is to cover or submerge useful signals with noise or similar jamming signals to prevent radar from detecting target signals. In order to evaluate the influence of suppression jamming on airborne warning radar, the influence of suppression jamming on the detection probability and detection distance of warning radar is analyzed. The variation of radar detection range and detection probability in complex electromagnetic environment compared with normal detection is given by flight test. It also provides a reference for evaluating the anti-jamming ability of airborne warning radar after being suppressed.
Abstract: Modern warfare is carried out in a complex electromagnetic environment, where noise suppression interference directly affects the detection ability of airborne warning radar to target, in order to make airborne warning radar play its due role in battlefield. More and more requirements are put forward for radar combat capability in complex electroma...
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Application of Dynamic Threshold in a Lake Ice Detection Algorithm
Peter Dorofy,
Rouzbeh Nazari,
Peter Romanov
Issue:
Volume 6, Issue 2, December 2018
Pages:
64-73
Received:
23 July 2018
Accepted:
2 August 2018
Published:
29 August 2018
Abstract: The traditional method involved in the classification of surface types such as water, ice, and snow rely on thresholds values of spectral properties that are fixed. However, the use of daily fixed thresholds leaves a substantial number of either unclassified and/or misclassified ice and water pixels. In this study, a new dynamic threshold technique is proposed to identify and map lake ice cover in the imagery of GOES-I to P series satellites. In addition, dynamic threshold can be used as an alternative solution to Bidirectional Reflectance Distribution Function (BRDF) models. The technique has been applied using GOES-13 imager data over Lake Michigan, one of five of the Great Lakes. Nine scenes based on an hourly acquisition of a single day are used to visually sample water and ice pixels. A threshold for the visible (0.62 µm) and the reflective component of the mid-infrared (3.9 µm) is determined for each scene by the intersection of the probability distributions of the water and ice samples. The thresholds are used as decision thresholds in a binary test algorithm applied on a per-pixel basis. Both fixed threshold (single scene) and dynamic thresholds (multiple scenes) have been compared. Dynamic threshold shows a significant gain in classified pixels over fixed threshold. A preliminary quantitative assessment is introduced to evaluate the algorithm’s performance using sensitivity and specificity testing. The classification results show a sensitivity of 98% when delineating thick ice and water and 87% when delineating thick/thin ice and water. Implementing a dynamic threshold, can be used in constructing ice maps in applications that benefit from high temporal resolution imagery.
Abstract: The traditional method involved in the classification of surface types such as water, ice, and snow rely on thresholds values of spectral properties that are fixed. However, the use of daily fixed thresholds leaves a substantial number of either unclassified and/or misclassified ice and water pixels. In this study, a new dynamic threshold technique...
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An Assessment of the Role of Water Hyacinth in the Water Level Changes of Lake Naivasha Using GIS and Remote Sensing
Peter Odoyo Agutu,
Moses Karoki Gachari,
Charles Ndegwa Mundia
Issue:
Volume 6, Issue 2, December 2018
Pages:
74-88
Received:
19 August 2018
Accepted:
19 October 2018
Published:
19 November 2018
Abstract: Lake Naivasha is an important water resource for Kenya being a fresh-water lake in a region dominated by salty-water lakes. The lake supports several human activities around it. Its water level, though fluctuates, was gradually declining before 2010. The water level rose from March 2010 and has since remained relatively high. As a result, areas around the lake that were previously land surface are currently submerged in water. This is threatening the survival of human activities around the lake. Consequently, the study sought to establish the causes of the lake’s water level fluctuations in the period 2000-2016, focusing on the role of rainfall, temperature, human activities around the lake, and water hyacinth. Surface area of the lake covered by water and surface area of the lake covered by water hyacinth were extracted from Landsat images. The SEBAL model was used to estimate evaporation potential over the lake and differences in evaporation over areas covered by water hyacinth and open water surfaces were analysed. Water hyacinth cover was found to have significant, positive correlation with monthly average water levels (p < .05). Open water surfaces lost significantly higher water volume through evaporation than areas covered by water hyacinth (p < .05). This suggests that water hyacinth contributes to the high water levels. Rainfall received over Nyandarua slopes, which is the catchment region for in-flow rivers was also an almost statistically significant contributor to lake’s water level changes, while temperature was not. On the other hand, growing human activities around the lake seemed to contribute to water level decline through increasing abstraction from the lake. The study recommends more research on, and implementation of better and more ecologically efficient measures for controlling water hyacinth growth in Lake Naivasha.
Abstract: Lake Naivasha is an important water resource for Kenya being a fresh-water lake in a region dominated by salty-water lakes. The lake supports several human activities around it. Its water level, though fluctuates, was gradually declining before 2010. The water level rose from March 2010 and has since remained relatively high. As a result, areas aro...
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Very High Resolution Mapping with the Pléiades Satellite Constellation
Roland Perko,
Hannes Raggam,
Mathias Schardt,
Peter Michael Roth
Issue:
Volume 6, Issue 2, December 2018
Pages:
89-99
Received:
16 August 2018
Accepted:
30 November 2018
Published:
24 December 2018
Abstract: The Pléiades satellite constellation provides very high resolution multi-spectral optical data at a ground sampling distance of about 0.7 m at nadir direction. Due to the highly agile pointing angle capacity in the range of ±47 degrees the sensors are optimal for detailed earth observation. They are able to collect stereo and tri-stereo datasets in one overflight with a swath width of 20 km. Such images allow 3D mapping of any region on the Earth’s surface at very high resolution with high accuracy, where the reconstruction of the heights is based on along-track stereo. This work presents methodologies and workflows within the fields of remote sensing and computer vision that are used (1) to densely reconstruct digital surface models (DSM), (2) to derive digital terrain models (DTM), and (3) to generate multi-spectral ortho-rectified products. Within this process, the accuracy of the geometric sensor models, given as rational polynomial coefficient (RPC) models, plays a crucial role. Therefore, an assessment is performed on two distinct test sites discussing the initial 2D geo-location accuracy of the given sensor models. An optimization scheme is presented to adjust the given RPC models yielding 3D geo-location accuracies of 0.5 m in planimetry and 1 m in height. In the frame of surface model generation important issues like epipolar rectification, hierarchical stereo matching, and fusion of heights are reported. The main outcomes are that the sensor accuracy is within the range as defined by Astrium, but that a sensor model optimization is obligatory when it comes to highly accurate 3D mapping. The presented workflow generates mapping products with a GSD of 0.5m. The derived DSMs and DTMs show a high level of detail, thus enabling varying applications on a large scale, like land cover and land use classification, change detection, city modelling, or forest assessment.
Abstract: The Pléiades satellite constellation provides very high resolution multi-spectral optical data at a ground sampling distance of about 0.7 m at nadir direction. Due to the highly agile pointing angle capacity in the range of ±47 degrees the sensors are optimal for detailed earth observation. They are able to collect stereo and tri-stereo datasets in...
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