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Register a new userPreprocessing of Landsat Imageries Used to Mapping NDVI in North Lattakia Forests
المعالجة المسبقة لصور لاندسات المستخدمة لرسم خريطة NDVI في غابات شمال اللاذقية
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Tishreen University ورقة بحثية
Publication date
2018
fields
Forestry and Ecology
and research's language is
العربية
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هدف البحث إلى توضيح خطوات المعالجة المسبقة اللازمة للصور الفضائية قبل البدء بتحليل و استخراج البيانات منها، و ذلك باستخدام برنامج .ENVI حيث طُبق التصحيح الشعاعي و التصحيح الطبوغرافي على صورة لاندسات أُخذت في العام 2017، و من ثم قمنا بحساب مؤشر الاختلاف النباتي القياسي NDVI لهذه الصورة قبل و بعد تطبيق المعالجة المسبقة. أظهرت النتائج وجود فرق في القيم الطيفية للصورة قبل و بعد التصحيح الإشعاعي خاصة في مجال الطيف تحت الأحمر القريب، حيث سجلت قيم الانعكاس في الصورة الأصلية بين (40- 150)، في حين تراوحت هذه القيم بين (300- 3500) في الصورة المصححة. كما بدا الفرق واضحاً في قيم الانعكاس ضمن القناتين الحمراء و تحت الحمراء القريبة، بعد إجراء التصحيح الطبوغرافي، خصوصاً في النقاط الموجودة في ظل التضاريس. كما لوحظ وجود اختلافات في قيم مؤشر الاختلاف النباتي القياسي NDVI للصورة 2017 قبل و بعد تطبيق المعالجة المسبقة على الصورة الفضائية، خاصة في النقاط ذات التغطية النباتية الجيدة و الجيد جداً و التي تتميز بقيم مرتفعة للمؤشلر النباتي NDVI. خلصت الدراسة إلى أهمية اتباع و تطبيق أقل عدد مطلوب من خطوات المعالجة المسبقة للصور، و ذلك لنتجنب الحصول على معلومات غير حقيقية عن الظاهرة المدروسة و بالتالي الوصول إلى استنتاجات غير صحيحة.
The aim of the research was to clarify the pre-processing steps required for satellite images before starting to analyze and extract data from them using the ENVI program. Radiometric and topographic correction applied to the Landsat image 2017, and then we calculated the NDVI index for this image before and after applying pre-processing. The results showed a difference in the spectral values of the image before and after the radiometric correction, especially in near infrared band. The reflection values were recorded in the original image between (40-50) and (300-3500) in the corrected image. The difference in the reflection values after the topographical correction was also visible on the near- infrared and infrared bands, especially in the points where shadows of the terrain. Differences in the values of NDVI for 2017 were observed before and after the application of pre-processing on the image, especially in points of good and very good vegetation coverage with high values of the index. The study concluded that it is important to follow the minimum number of steps required for preprocessing steps in order to avoid unnecessary steps and recommend well tested, readily available, and adequately documented data approaches and data products.
References used
BAKR, N.; WEINDORF, D.C.; BAHNASSY, M.H.; MAREI, S.M.; EL-BADAWI, M.M. Monitoring land cover changes in a newly reclaimed area of Egypt using multi-temporal Landsat data. Applied Geography. 2010. Vol. (30): 592–605
BODART, C. H.; EVA, R.; BEUCHLE, R.; RAŠI, D.; SIMONETTI, H.-J.; STIBIG, A.; BRINK, E.; LINDQUIST, F.; ACHARD. Pre- Processing Of A Sample Of Multi- Scene And Multi- Date Landsat Imagery Used To Monitor Forest Cover Changes Over The Tropics. ISPRS Journal of Photogrammetry and Remote Sensing. 2011. Vol. (66):555–563
CHANDER, G.; MARKHAM, B. L.; HELDER, D. L. Summary of current radiometric calibration coefficients for Landsat MSS, TM, ETM+, and EO- 1 ALI sensors. Remote Sensing of Environment. 2009. Vol. (113): 893–903
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