نوع مقاله : مقاله پژوهشی

نویسندگان

• فائزه سلیمانی وسطی کلایی ¹
• مهدی آخوندزاده هنزائی ²

¹ دانشجوی کارشناسی ارشد سنجش از دور دانشگاه تهران

² استادیار گرایش سنجش از دور دانشکده مهندسی نقشه برداری و اطلاعات مکانی دانشگاه تهران

چکیده

دمای سطح زمین و گسیلندگی دو ویژگی فیزیکی مهم از سطح زمین هستند. محاسبه دمای سطح زمین اهمیت زیادی در مطالعات محیطی، هواشناسی، بررسی تبخیر و تعرق و فعل و انفعالات بین زمین و جو دارد .در سالیان اخیر تصاویر ابرطیفی حرارتی به دلیل دارا بودن تعداد زیاد باندهای حرارتی در مقایسه با تصاویر فراطیفی، به یک ابزار قدرتمند برای تخمین دمای سطح زمین تبدیل شده‌اند. هدف اصلی در این تحقیق تهیه نقشه‌های حرارتی و گسیلندگی بااستفاده از دو روش مجزای TESوARTEMISS از تصاویر سنجنده ابر طیفی حرارتی هواییHyTES وهمچنین تخمین پارامترهای جوی در این تصاویر می‌باشد. نوآوری اصلی این تحقیق پیاده ‌سازی روش‌هایTESوARTEMISSبرای اولین بار روی داده ابرطیفی های ‌تس است و همچنین در این تحقیق، پارامترهای جوی مورداستفاده درARTEMISSاز روش آیزاک بدست آمده است. اینتحقیقشاملسهمرحله‌اصلیاست. درمرحله اول بعد از حذف باندهای نویزی تصویر و انتخاب 202 باند بهینه،الگوریتم SETکه شامل مدل‌هایMMD, NEMوRATIOمی ‌باشد، بر روی تصویر اعمال شدند.  در مرحله دوم با استفاده از تصحیح جوی آیزاک، پارامترهای جوی از قبیل گذردهی جوی و رادیانس مسیر محاسبه شدند. در مرحله آخر الگوریتم ARTEMISSبه منظور تخمین دما و گسیلندگی، بر روی این نوع تصویر اعمال شد.  در پایان جهت ارزیابی روش ‌های پیشنهادی از محصولات دما و گسیلندگی سنجنده HyTES که توسط ناسا عرضه می‌گردد، استفاده شد. نتایج ارزیابی نشان می‌دهد که RMSEدما برای روش‌هایTES وARTEMISSبه ترتیب برابر با  6/0 و 2/1 درجه کلوین و برای گسیلندگی نیز در باند نمونه  177 به ترتیب در دو روش  01/0 و 02/0 می ‌باشد. نتایج حاصل نشان می‌ دهند که الگوریتم‌هایTESوARTEMISS،روش‌های کارآمدی در تخمین دما و گسیلندگی می ‌باشند.

کلیدواژه‌ها

• دمای سطح زمین
• گسیلندگی
• TES
• ARTEMISS
• سنجنده ابرطیفی حرارتی HyTES

20.1001.1.25883860.1397.27.107.7.3

عنوان مقاله [English]

Emissivity and land surface temperature mapping fromHyTES thermal hyperspectral images using TES and ARTEMISS algorithms

نویسندگان [English]

• faeze Soleimani vosta kolaei ¹
• Mehdi Akhoondzadeh Hanzaei ²

¹ M.Sc. student of Remote Sensing Division, School of Surveying and Geospatial Engineering, College of Engineering, University of Tehran, Iran

² Assistant Professor, Remote Sensing Division, School of Surveying and Geospatial Engineering, College of Engineering, University of Tehran, Iran

چکیده [English]

Extended abstract
Land Surface Temperature (LST) and Emissivity are two significant physical features of the Earth’s surface and atmosphere. The calculation of land surface temperaturehas a great significance in environmental studies, meteorology, evapotranspiration study, interactions between land surface and the atmosphere, detection of earthquake- related thermal anomalies, monitoring the drought,  fire and energy balance models on the surface of the earth on a regional and global scale.The use of remote sensing technology and types of satellite images as one of the most important sources of data collection to study and monitor the land and environmental resources has attracted the attention of many experts and specialists of various sciences including environment, meteorology, hydrology, etc. in recent years.In recent years, hyperspectralthermal images have become a powerful tool for estimation of the land surface temperature due to the large number of thermal bands. The main purpose of this research is to obtain land surface temperature and emissivity using two distinct methods of TES (Temperature/Emissivity Separation Algorithm) and ARTEMISS (Automatic Retrieval of Temperature and emissivity using Spectral Smoothness) from the HyTES thermal hyperspectral images. The HyTES (Hyperspectral Thermal Emission Spectrometer) is an airborne thermal hyperspectral sensor with 256 spectral channels within the range of 7.5 and 12 micrometers in the range of thermal infrared of the electromagnetic spectrum designed by NASA.
The scope of this study was to retrieve land surface temperature, emissivity and atmospheric parameters from the HyTES sensor in two different methods: ARTEMISS and TES. We used the ISAC method that estimates the transmission and upwelling radiance of the atmosphere. In ISAC method, it is necessary to fit a straightforward line to optimize upper boundary of data. We used the smoothness of the spectral emissivity in the ARTEMISS algorithm in order to retrieve temperature and emissivity. Atmospheric parameters that were obtained from ISAC were used in ARTEMISS and TES. In the next step, the TES algorithm was applied to derive surface emissivity and LST. This method is designed to reduce systematic errors in LST and LSE and also to limit errors in the amplitude and shape of emissivity spectra. This algorithm first estimates the normalized emissivity and then, calculates emissivity band ratios. Next, anempirical relationship predicts the minimum emissivity from the spectral contrast (MMD) of the normalized values, permits recovery of the emissivity spectrum with improved accuracy by using an empirical relationship between emissivity contrast and minimum emissivity, the nondeterministic problem of TES was solved. The basic problemof TES is, as indicated by Realmuto 1990 that we obtain  spectral measurements of radiance and need to find unknowns ( emissivities and one temperature). This is a nondeterministic problem, so at least one additional constraint must be considered. Several methods have been developed to resolve these problems such as Normalized Emissivity Method (NEM), RATIO and Minimum-Maximum emissivity Difference (MMD). In the NEM module of TES, we guessed preliminary values of temperature and LSE assuming a value for the maximum local emissivity (for blackbodies). Then, in RATIO module, we estimated emissivity normalized spectrum (). In order to scale the  spectrum to actual emissivity values, we used the MMD module of TES. After applying NEM, RATION and MMD module, TES estimates and reports pixel-by-pixel precisions for LST and LSE. Finally, we compared the results of LST and LSEs derived from these algorithms with products of HyTES. The results shown in this study prove the feasibility of retrieving accurate estimates of atmospheric parameters, surface temperature and emissivity with HyTESdata.It should be noted that the noise and water vapor absorption bands of HyTEShyperspectral image were removed, therefore, 202 optimal bands were selected. Then, TES algorithm consists of modules NEM, MMD and RATIO was applied. ARTEMISS method is based on (1) in-scene atmospheric transmission estimation, (2) matching of the transmission to a database and (3) retrieving a spectrally smooth emissivity by an iterative method used on hyperspectral data. The ARTEMISS algorithm was applied. The final outputs of these two algorithms include thermal and emissivity images. In order to evaluate these two methods and quality assessment, we used the satellite products that have been prepared by NASA. The results of the quality assessment show that temperature RMSE for TES and ARTEMISS methods are 0.6 and 1.2 kelvin respectively, and also emissivity RMSE for band 171 are 0.01 and 0.02 respectively. Therefore, TES algorithm is a more accurate method than ARTEMISS which was implemented for the first time on this type of data.The obtained results show that the thermal hyperspectral data are suitable for accurate retrieval of emissivity and land surface temperature in any kind of land cover.

کلیدواژه‌ها [English]

• LST
• Emissivity
• TES
• ARTEMISS
• HyTES
• Thermal Hyperspectral Scanner