چکیده:
جابه جایی تپه های ماسه ای تهدیدی دائمی برای زیرساخت های حمل و نقل، اراضی کشاورزی، و سکونتگاههای پیرامون پلایای دامغان است. با وجود پژوهش های انجام شده در این منطقه، با هدف منشایابی رسوبات بادی، تحقیق حاضر دیدگاهی متفاوت برای ارزیابی مقادیر و جهت حرکت تپههای ماسه ای به وسیلة سنجش تغییرات همدوسی راداری و طبقه بندی شیءگرا ارائه میدهد. در این تحقیق، ضمن بررسی کتابخانه ای، از روشهای دورسنجی و پیمایشی برای دستیابی به اهداف استفاده شده است. نخست دادههای راداری 2017 و 2018 برای سنجش تغییر مقادیر همدوسی و شناسایی تپههای فعال و تعیین واحد کاری تحلیل شد. با توجه به پراکنش نامنظم تپه های ماسه ای، واحد کاری به 16 بلوک دارای یک تپه شاهد تقسیم شد. سپس، پردازش تصاویر Bird's eye و Geo eye با هدف استخراج جبهة بادپناه به عنوان محل استقرار تپه ها در سالهای 2003 و 2016 به وسیلة طبقه بندی شیءگرا انجام گرفت. سپس، با استفاده از لایه های مستخرج، مقادیر جابه جایی توسط مدل بهینه شدة گای استخراج و آزیموت محاسبه شد. یافته ها مقادیر جابه جایی 4/22 متری، با آزیموت 135 درجه را در بازة زمانی سیزده ساله نشان می دهد. اعتبارسنجی یافتهها با خروجی تحلیل آماری جهت باد در همین بازه و مقایسة آن با خروجی پردازشها بیانگر انتخاب صحیح قطعة شاهد بوده است.
Damage caused by the sand dunes movement is one of the most important environmental and socio-economic issues in desert region. erosion and wind processes study began with the work of Bagnold (1954). After significant advances in laboratory and physical approaches to the elements and forces involved in wind erosion and at the contemporary with the development of remote sensing tools and data and changes in methods and algorithms for interpreting aerial photographs and satellite images, the rapid emergence of planetary geomorphology and the search for analogies and similarities on other planets. Rapid developments in the geomorphology of wind processes took place. Using Landsat, ASTER and Quick bird images and LIDAR data, many studies have been done to classify sand dunes. After the launch of two ERS remote sensing radar satellites in 1991 and 1995, the value of CCD Was considered. But in Iran, most of the studies conducted in the desert region, such as the Damghan playa, have studied the changes in long-term periods, which are mainly of sediment origin and classified sand dunes using multispectral satellite data. The aim of this study was to use Sentinel-1 IW SAR time series data in arid regions to detect surface changes in the short term due to wind morph dynamic activity and on the other hand to evaluate the effectiveness of using both radar and optical data and Object-oriented classification model in the events and morphological changes detection of sand surfaces and forms. the results obtained from the processing of remote sensing data and classification and achieving the dimensions of sand dune mobility with the results of wind data analysis will be evaluated and verified.Materials and methodsDamghan plain located in Damghan plain with longitude 54 10 to 54 40 east and latitude 36 36 to 36 10 north has a hot and dry desert climate and an average rainfall of 100 mm per year, which due to the desert nature, is prone to wind morph dynamic performance. Therefore, in the present study, we aimed to evaluate the mobility of sand dunes as part of the natural hazards active in the region. The research method is library, remote sensing and surveying. Data analysis is based on two main concepts; segmentation and classification. Initially, based on geological and topography maps and field survey, geomorphology maps were created. Then based on the prepared and adapted maps and field surveillance, sandy forms were limited. Then, in order to determine the working units, using the CCD technique with Sentinel-1 radar images, the active and inactive parts of the sand forms were detected. Two radar interfrograme (Master and slave) related to the two dates of 14/05/2017 and 22/03/2018 were used to extract the CCD (based on phase difference).Finally, with the identification of work units, automatic detection and extraction of sand dunes was targeted, and for this purpose, the bottom-up hierarchical object-oriented method and top-down classification using the growing region technique was used. Also, by extracting sand dunes using object-oriented classification, the values and direction of moving the dune were extracted using Guy, 1995 optimized model and the corresponding sand rose were drawn. Wind rose analysis and drawing related to wind statistics of Damghan synoptic station (the closest meteorological station to the study area) in the statistical period of 1384-96 was also performed with the aim of verifying the findings of the previous step.Result and discussionA: Extract sandy formsImage enhancement is the first step in preparing an image for the extraction of image elements (including sand dunes). Due to the importance of the dune slip face, in the process of identifying the displacement and sand dunes movement, and its lower compaction coefficient than other parts of a sand dune, in order to detection This enhance method, by using the most abundant discontinuity search, distinguishes brighter borders that forming sand dune steep slope from other parts of dune and around environments. The output of this filter is an image in which the sand dunes slip face, with different radiometric intense, is marked from the surrounding sand surfaces.B: Detecting and extracting sand dunesIn order to evaluate the displacement amount and direction, the object-oriented classification paradigm was used to automatically detect the edges as dune front. Instead of just evaluating pixels, the spatial pattern of objects and forms is also considered. Therefore, the initial segmentation was performed using a scale factor "100" that determined the maximum heterogeneity in the diagnosis of the forms. in addition to using radiometric values, classes can be formed based on geometry and related elements. The rules used are Brightness and Compactness. First, by analyzing the values of average brightness with a threshold of 165, the overall sand dune pattern as the first layer was created. Then, using the Compactness rule, the pixels that were recognized as the dune slip face by the spectral feature in the previous step were eliminated from the classes.C: calculation the sand dunes amount and direction displacement.Sand dunes displacement calculated by considering the end edge, as the progressive edge at successive times and measuring the distance between two consecutive lines in two consecutive years. To evaluate the dunes movement direction, the axis of symmetry of each hill was selected as the main axis and the initial and final point of this line on the downwind front of sand dunes in both the first and last years were considered. The azimuth line or the direction of movement relative to the north was drawn and this angle was calculated and its sand rose with an angle of 135 degrees was drawnConclusion This study, suggested a new approach to detect sand dynamics using radar InSAR techniques and object-oriented classification using high resolution optical images. The results of InSAR processing, and CCD technique, was able to recognize active and inactive sand dunes dynamic, and display them in continuous numerical values (fully active to fully stabilized hills).The application of OBIA on Bird’s eye and Geo eye images (2003-2016) results, indicates that the 22.4 m movement of hills is mainly in the southwest direction in a period of 13 years and 1.7 m for each year. The result of comparing wind rose (wind data analysis) and sand rose (sand movement data analysis) shows a significant relationship between 80% of northwest-southeast wind frequency in relation to 135 ° azimuth for 75% of sand dunes movement and 15% of north-south wind frequency in relation to 180° azimuths of 25% of sand dunes movement.
خلاصه ماشینی:
با وجود پژوهش هاي انجام شده در اين منطقه ، با هـدف منشـأيابي رسـوبات بـادي، تحقيق حاضر ديدگاهي متفاوت براي ارزيابي مقادير و جهت حرکت تپه هاي ماسه اي بـه وسـيلۀ سـنجش تغييـرات همدوسي راداري و طبقه بندي شي ءگرا ارائه ميدهد.
عطامرادي (١٣٧٨)، زهتابيان و همکاران (١٣٨٢)، علويپناه و همکاران (١٣٨٣)، و مرتضايي فريزهندي و شهبازي(١٣٩٠) نيز در پژوهش هايشان با استفاده از داده هاي دورسنجي چندطيفي و عمليات صحرايي به ارزيابي و طبقه بندي تپه هاي ماسه اي پرداخته اند.
از همين رو در پژوهش حاضر براي شناخت مورفوديناميک باد و ارزيابي جهت و مقادير جابه جايي تپه هاي ماسه اي به مثابۀ پديدة پوياي مورفولوژيک قرار است در قدم اول با استفاده از داده هاي راداري IW١ سنتينل ١ با قدرت تفکيک مکاني کمتر از پانزده متر و تکنيک CCD اشکال و سطوح پويا و غيرپوياي ماسه اي شناسايي شود.
اساس ايده در تکنيک CCD بر اين حقيقت استوار است که در مناطق مشخص و براي زماني معلوم همۀ تغييرات ايجادشده در يک چشم انداز مي تواند با استفاده از داده هاي راداري SLC١ و با استخراج اطلاعات و مقادير همدوسي آشکارسازي شود.
Investigation of the shape and type of sand dunes in order to harness wind erosion in Damghan erg, Tehran University, Kavir and Desert Research Center of Iran, Master's thesis.
ESP: a tool to estimate scale parameter for multiresolution image segmentation of remotely sensed data, International Journal of Geographical Information Science, Vol. 24, No. 6, PP.