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991.
992.
Land cover and land use classification performance of machine learning algorithms in a boreal landscape using Sentinel-2 data 总被引:1,自引:0,他引:1
Abdulhakim Mohamed Abdi 《地理信息系统科学与遥感》2020,57(1):1-20
ABSTRACTIn recent years, the data science and remote sensing communities have started to align due to user-friendly programming tools, access to high-end consumer computing power, and the availability of free satellite data. In particular, publicly available data from the European Space Agency’s Sentinel missions have been used in various remote sensing applications. However, there is a lack of studies that utilize these data to assess the performance of machine learning algorithms in complex boreal landscapes. In this article, I compare the classification performance of four non-parametric algorithms: support vector machines (SVM), random forests (RF), extreme gradient boosting (Xgboost), and deep learning (DL). The study area chosen is a complex mixed-use landscape in south-central Sweden with eight land-cover and land-use (LCLU) classes. The satellite imagery used for the classification were multi-temporal scenes from Sentinel-2 covering spring, summer, autumn and winter conditions. Using stratified random sampling, each LCLU class was allocated 1477 samples, which were divided into training (70%) and evaluation (30%) subsets. Accuracy was assessed through metrics derived from an error matrix, but primarily overall accuracy was used in allocating algorithm hierarchy. A two-proportion Z-test was used to compare the proportions of correctly classified pixels of the algorithms and a McNemar’s chi-square test was used to compare class-wise predictions. The results show that the highest overall accuracy was produced by support vector machines (0.758 ± 0.017), closely followed by extreme gradient boosting (0.751 ± 0.017), random forests (0.739 ± 0.018), and finally deep learning (0.733 ± 0.0023). The Z-test comparison of classifiers showed that a third of algorithm pairings were statistically different. On a class-wise basis, McNemar’s test results showed that 62% of class-wise predictions were significant from one another at the 5% level or less. Variable importance metrics show that nearly half of the top twenty Sentinel-2 bands belonged to the red edge (25%) and shortwave infrared (23%) portions of the electromagnetic spectrum, and were dominated by scenes from spring (38%) and summer (40%). The results are discussed within the scope of recent studies involving machine learning and Sentinel-2 data and key knowledge gaps identified. The article concludes with recommendations for future research. 相似文献
993.
994.
The Nador lagoon ecosystem (North-East of Morocco) displays a major socioeconomic interest. In fact, it is essential to evaluate consequences of anthropogenic activities in the lagoon especially by organic matter studies (nature and distribution) in the sedimentary compartment. Surface sediments show variable rates in total organic carbon and in sulfur, high in some cases (7.5 and 1.8% respectively). These high contents are recorded in the center of the lagoon. Their distributions are controlled by the hydrodynamism and the anthropogenic degree. The molecular biomarkers analyses and especially n-alkanes distribution reveal: a zone of marine influence; and a zone of continental influence. The occurrence of pentacyclic triterpanes with a typical distribution of a thermally mature organic matter reveals a contamination due to petroleum products in the entire lagoon except for the center. Coprostanol occurrence near cities indicates wastewater effluents inputs and reducing conditions underlined by high values of stanols/sterol ratios. Thus, the organic contamination (petroleum by-products and wastewater effluents) occurs in the vicinity of the cities whereas the littoral edge and center remain weakly affected by these contaminations. 相似文献
995.
996.
Attwa Mohamed El Mahmoudi Ahmed Elshennawey Ahmed Günther Thomas Altahrany Ayman Mohamed Lamees 《Natural Resources Research》2021,30(5):3407-3428
Natural Resources Research - Soil characterization in coastal areas is essential for strategic coastal engineering implementation and for understanding the paleo-environmental conditions. However,... 相似文献
997.
Mohamed A. El-Sadek 《Journal of Applied Geophysics》2009,67(1):34-43
The purpose of this research is to study the signatures of a gold mine (Um Salim), located in the Eastern Desert of Egypt, using aeroradiospectrometric and aeromagnetic data. To achieve this goal, reduction-to-pole (RTP), high-pass filtering and analytical signal techniques were applied to the aeromagnetic data. Besides, interpretation of the total-count (TC) radiometric map, the three radioelements (K, eU and eTh) maps and the ternary radioelement composite image were carried out. Moreover, a two-dimensional trend analysis for the structural lineaments as traced from the geologic, total-count radiometric and reduced-to-pole magnetic maps was conducted to define the relationship which might exist between location of the gold mine, lithologies and major structures of the area under consideration.The study revealed that the known gold mine is associated with a high positive magnetic anomaly that trends in the NE direction and a high-amplitude analytic signal. The Um Salim gold mine is associated with very low aeroradiospectrometric levels on the four maps (TC, K, eU and eTh). The location of the gold mine is controlled by the intersection of both NW and NE trends. There are other particular radiospectrometric ratio signatures for gold deposits (eU/eTh, eU/K and eTh/K). Ternary radioelement maps can discriminate also alteration zones in various degrees that correlate with the gold mine. These zones can be used as a diagnostic exploration guide for various types of non-radioactive mineral deposits (e.g., copper and gold). Four major tectonic trends were identified that have the following directions: NE, NW, N–S and WNW. 相似文献
998.
Ahmed Mebarki Mehdi Boukri Abderrahmane Laribi Mohammed Farsi Mohamed Belazougui Fattoum Kharchi 《Journal of Seismology》2014,18(2):331-343
When dealing with structural damages, under the effect of natural hazards such as earthquakes, it is still a scientific challenge to predict the potential damages, before occurrence of a given hazard, as well as to evaluate the damages once the earthquake has occurred. In the present study, two distinct methods addressing these topics are developed. Thousands (~54,000) of existing buildings damaged during the Boumerdes earthquake that occurred in Algeria (Mw?=?6.8, May 21, 2003) are considered in order to study their accuracy and sensitivity. Once an earthquake has occurred, quick evaluations of the damages are required in order to distinguish which structures should be demolished or evacuated immediately from those which can be kept in service without evacuation of its inhabitants. For this purpose, visual inspections are performed by trained and qualified engineers. For the case of Algeria, an evaluation form has been developed and is still in use since the early 80s: Five categories of damages are considered (no damage or very slight, slight, moderate, major, and very severe/collapse). This paper develops a theoretical methodology that processes the observed damages caused to the structural and nonstructural components (foundations, roofs, slabs, walls, beams, columns, fillings, partition walls, stairways, balconies, etc.), in order to help the evaluator to derive the global damage evaluation. This theoretical methodology transforms the damage category into a corresponding “residual” risk of failure ranging from zero (no damage) to one (complete damage). The global failure risk, in fact its corresponding damage category, is then derived according to given combinations of probabilistic events in order to express the influence of any component on the global damage and behavior. The method is calibrated on a set of ~54,000 buildings inspected after Boumerdes earthquake. Almost 80 % of accordance (same damage category) is obtained, when comparing the theoretical results to the observed damages. For pre-earthquake analysis, the methodology widely used around the world relies on the prior calibration of the seismic response of the structures under given expected scenarios. As the structural response is governed by the constitutive materials and structural typology as well as the seismic input and soil conditions, the damage prediction depends intimately on the accuracy of the so-called fragility curve and response spectrum established for each type of structure (RC framed structures, confined or unconfined masonry, etc.) and soil (hard rock, soft soil, etc.). In the present study, the adaptation to Algerian buildings concerns the specific soil conditions as well as the structural dynamic response. The theoretical prediction of the expected damages is helpful for the calibration of the methodology. Thousands (~3,700) of real structures and the damages caused by the earthquake (Algeria, Boumerdes: Mw?=?6.8, May 21, 2003) are considered for the a posteriori calibration and validation process. The theoretical predictions show the importance of the elastic response spectrum, the local soil conditions, and the structural typology. Although the observed and predicted categories of damage are close, it appears that the existing form used for the visual damage inspection would still require further improvements, in order to allow easy evaluation and identification of the damage level. These methods coupled to databases, and GIS tools could be helpful for the local and technical authorities during the post-earthquake evaluation process: real time information on the damage extent at urban or regional scales as well as the extent of losses and the required resources for reconstruction, evacuation, strengthening, etc. 相似文献
999.
Mehdi Boukri Mohammed Naboussi Farsi Ahmed Mebarki Mohamed Belazougui Omar Amellal Brahim Mezazigh Nabila Guessoum Hamid Bourenane Azzedine Benhamouche 《Bulletin of Earthquake Engineering》2014,12(6):2683-2704
Located at the North-Eastern part of Algeria (Tellian Atlas), Constantine has crucial administrative, economic, scientific and cultural importance. It has continuously experienced significant urban evolutions during the different periods of its history. The city is located in an active seismic region within Algeria and has been struck in the past by several moderate and strong earthquakes. The strongest earthquake recorded since the beginning of instrumental seismology took place on October 27, 1985 with a magnitude M \(_\mathrm{S}=\) 5.9. Constantine presents a high seismic risk, because of its dense housing and high population density (2,374 inhabitants/km \(^{2})\) . This requires a risk assessment in order to take preventive measures and reduce the losses in case of potential major earthquake. For this purpose, a scenario based approach is considered. The building damage assessment methodology adopted for the Algerian context is adapted from HAZUS approach. In the present case, the effective Algerian seismic code response spectrum (RPA 99/2003) is considered as a seismic hazard model. The prediction of the expected damages is performed for a set of almost 29,000 buildings. 相似文献
1000.
Hongtao Wang Tao Wang Bingru Zhang Fengting Li Brahima Toure Isaiah Bosire Omosa Thomas Chiramba Mohamed Abdel‐Monem Mahesh Pradhan 《洁净——土壤、空气、水》2014,42(8):1029-1035
Sustainable access to safe drinking water and basic sanitation is an important part of the millennium development goals (MDGs). For most African countries, an extensive effort is needed for the last three remaining years for the achievement of the MDGs, especially in Sub‐Saharan Africa. Current practices for water and wastewater treatment in Africa are insufficient to ensure safe water and basic sanitation. To address this challenge, joint efforts are needed, including transforming to green economy, innovating technologies, improving operation and maintenance, harvesting energy, improving governance and management, promoting public participation, and establishing water quality standards. 相似文献