Mohsen Pourkhosravani; Ali Mehrabi; Sadegh Karimi; Mina Azizi
Abstract
Extend AbstractIntroductionEnergy is considered to be one of the most important factors affecting the development of human societies and also an essential parameter in economic and social development along with the quality of life. Population growth, rising living standards, the risk of global ...
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Extend AbstractIntroductionEnergy is considered to be one of the most important factors affecting the development of human societies and also an essential parameter in economic and social development along with the quality of life. Population growth, rising living standards, the risk of global warming caused by greenhouse gas, acid rain, environmental problems and threats to human health, lack of fossil energy sources and rising energy consumption have increased interests in renewable energies. Solar energy has been used as a source of renewable energy for a long time. As one of the safest, most efficient and most economical sources of energy, it has the potential to become the main energy source in the near future (Dincer, 2000: 157). Due to the high number of sunny days, Iran is among the countries receiving the highest level of solar radiation in the world. With 240 to 250 sunny days per year, approximately 80 percent of the country receives an average annual solar radiation of 4.5 - 5.4 kWh / m² (Moghadam et al, 2011: 107). In this regard, the present study seeks to evaluate and monitor radiant energy reaching the surface of Sirjan basin. Materials & MethodsThe study area, Sirjan Basin, is located between 28 degrees and 46 minutes and 50 seconds to 29 degrees and 58 minutes and 1 second northern latitude, and 55 degrees and 11 minutes and 20 seconds to 56 degrees and 32 minutes and 40 seconds eastern longitude. It includes 18481 square kilometers with an average altitude of 1710 meters above sea level. Descriptive-analytical method has been used in the present applied research. Data are collected using library and documentary research methods (from information and statistics offered by different organizations) or extracted from satellite images. Solar radiation energy reaching to the surface of the study area has been evaluated using three methods including Angstrom experimental model, Solar Analyst method in GIS and Remote Sensing. Results & DiscussionAngstrom experimental model indicates that the maximum amount of energy directly received by the basin at low latitudes (28 degrees and 50 minutes) is 73370-73436 watts per square meter. This decreases as we move toward higher latitudes reaching 72836-72903 watts per square meter in the northern parts of the basin (latitude 29 degrees and 50 minutes). Monitoring solar radiation energy reaching the surface with GIS Solar Analyst (solar radiation analysis method) shows that the lowest amount of radiant energy reached the surface in January (between 14000 to 144039 watts per square meter). Also, the maximum amount of radiant energy reached the surface in July (between 111000 to 252000 watts per square meter). Remote sensing technique also shows that the amount of instantaneous radiation received in Sirjan basin reaches its minimum during winters and only a limited part in the west of the study area receives 4.498 to 8.436 watts per square meter. The maximum amount of instantaneous radiation received in summers is 597.6 to 845.6 watts per square meter, which is received in a large part of the west, northwest and southwest of the basin. ConclusionMonitoring radiant energy reaching the surface of Sirjan basin using experimental Angstrom model shows that the highest level of energy received in the southern parts of the basin is around 733370 to 73436 watts per square meter. This is reduced moving toward the northern parts of the basin. Moreover, solar radiation analysis method (Solar Analyst in GIS) shows that the highest amount of solar energy in Sirjan Basin is received in July with 200000 to 252000 watt-hours per square meter , June with 170000 to 248341 watt-hours per square meter, May with 190000 to 247627 watt-hours per square meter and August with 190000 to 234500 watt-hours per square meter, respectively. These values are recorded in eastern, northeastern and southeastern parts of the basin. Results indicate that the eastern half of the basin in which the cities of Balvard, Tekiye, Saadatabad and Pariz are located, receives the highest amount of solar radiation energy especially in summer. Remote sensing technique shows that the highest amount of instantaneous radiation received in summer is 597.6to 845.6 watts per square meter which is recorded in the western, northern, northwestern, southern and southern parts of the region including the villages of Pariz, Saadatabad, Balvard in the central strip and Khatunabad, Mahmoudabad, Najafabad, Malekabad and Golestan. The same is also recorded in other seasons, though with a decreasing trend. The highest level of instantaneous radiation is received in these parts of the basin.
Mostafa Khabazi; Ali Mehrabi; Javad Arabi
Abstract
Extended Abstract Introduction Digital elevation model (DEM) is the raster representation of the ground surface so that the information of each cell on the image has a value equal to the altitude from the sea level corresponding to the same spot on the ground. DEM is an appropriate tool for the generation ...
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Extended Abstract Introduction Digital elevation model (DEM) is the raster representation of the ground surface so that the information of each cell on the image has a value equal to the altitude from the sea level corresponding to the same spot on the ground. DEM is an appropriate tool for the generation of topographic maps and contour lines, access to the information of surface roughness, three dimensional vision, etc. (Jacobsen, 2004). The accuracy of the digital elevation model is effective on the accuracy of the information from which it is obtained. This is why researchers are always looking for a way to increase the accuracy of digital elevation models. Among the information resources that are used to generate this model are ground mapping, aerial photography, satellite images, radar data, and Lidar. Some of these data generate the digital elevation model with little accuracy due to the insufficiency of the elevation information. The aim of this paper is to investigate the accuracy of DEMs derived from ASTER satellite images and SRTM data with 30 and 90-meter pixel dimensions and the digital elevation model derived from the topographic 1:25000-scale maps with Differential Global Positioning System (DGPS) in different landforms including plains, hills and mountains. Materials and Methods The study area is a part of the project of dam and water transfer system from the Azad dam to the plain of Ghorve-Dehgolan (with the goal of transferring water from the catchments of Sirvan River into the country) in the province of Kurdistan and the city of Sanandaj. In this study, the Real-Time kinematic method (RTK) was used to locate the points. In this method, assuming that the coordinates of the reference station are known and comparing it with the location obtained from the GPS receiver, a correction value is obtained that is applied to the coordinates obtained for the Rover Station, which is known as the relative or differential method. In this method, the corrections are calculated asreal-time during the observations and are considered in the determination of the Rover location.The Leica GS10 GNSS receivers were used in this study. First, two reference stations were determined using the Fast Static method and then, the Real-Time kinematic (RTK) method was used. In order to investigate the extent of the data compliance and relation, the Pearson linear correlation analysis was used and the accuracy assessment of the extracted digital elevation models was carried out using the RMSE, mean error and standard deviation. Results & Discussion The statistical parameters such as root mean square error (RMSE), bias (µ) and standard deviation () were used to assess the accuracy of each one of the investigated digital models. By comparing different sources that create DEMs, it can be seen that the minimum error is first related to the digital elevation model extracted from the contour lines of the 1:25000-scale map (27/6 = RMSE) and then to the ASTER digital elevation model with the pixel size of 30 meters (RMSE=7.43). The 30-meter pixel size DEM has always led to better results than the 90- meter pixel size DEM. Based on the mean error standard, the minimum bias is related to ASTER30 m (bias of 2 m) and then to the 1: 25,000 DEM (2.17). The maximum bias was related to 30-and 90-meter models extracted from the SRTM data. The results of standard deviation error were in compliance with the RMSE results, which confirmed the superiority of 1:25000-scale map and ASTER30 m DEMs. The results showed that the determination coefficient of relationship between the ground data and digital elevation models is between 97 and 99. The maximum compliance is related to the digital elevation model extracted from the 1:25000-scale topographic data and the ASTER30 m DEM, while the minimum compliance is related to the SRTM90 m data. In general, the compliance of the digital elevation models with the ground data decreased as the field's conditions became more difficult, i.e. from plain to mountain. Conclusion The results of DEMs accuracy assessment showed that the minimum error was primarily related to 1:25000 contour lines DEM (RMSE=6.27) and then, to the ASTER30 m DEM (RMSE=7.43). The pixel size of 30 meters has always been better than the pixels size of 90 meters. Based on the mean error standard, the minimum bias is related to the ASTER 30 m (bias of 2 m) and then, to the 1: 25,000 DEM (2.17). The maximum bias was related to 30-and 90-meter models extracted from the SRTM data. The results of the standard deviation error were consistent with the RMSE results, which confirmed the superiority of the digital elevation models extracted from the topographic 1:25000-scale maps and the ASTER30 m DEM.
