研究目的
To demonstrate the feasibility of using a two-platform measurement system (BLIMP and ZiviCat) with image processing algorithms to obtain Lake Surface Water Temperature (LSWT) patterns at sub-pixel satellite scales on Lake Geneva.
研究成果
The two-platform system and image processing procedure successfully generated high-resolution LSWT maps at sub-pixel scales, revealing spatial variability with unprecedented detail. High overlap is essential for accurate thermography in low-contrast scenes. This approach can advance understanding of lake processes and improve satellite data validation.
研究不足
The methodology requires high overlap (~95%) between images for effective noise reduction and registration, which may not be feasible in all conditions. The low contrast of LSWT scenes makes noise correction challenging, and artifacts may remain. The system is less effective under strong wind conditions due to platform movement. Radiometric calibration relies on in situ measurements, which can be contaminated by boat tracks.
1:Experimental Design and Method Selection:
A two-platform system was used, with BLIMP for airborne thermal imagery and ZiviCat for in situ temperature measurements. Image processing included nonuniformity correction (NUC) using a two-point linear method, drift correction via PDF matching, and image registration using feature detection (SURF and MSER algorithms) and MLESAC for geometric transformation. Image fusion was done by averaging overlapped images.
2:Sample Selection and Data Sources:
Field campaigns on Lake Geneva, with data from March 18, 2016, covering a ~16 km trajectory. Images had ~0.8 m pixel resolution and high overlap (~95%).
3:8 m pixel resolution and high overlap (~95%).
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: BLIMP equipped with FLIR Tau2 LWIR camera (640x512 pixels, 14-bit), Raspberry Pi RGB camera, GPS, IMU, communication modules; ZiviCat with RBRsolo temperature sensors (10 thermistors), GPS, IMU; balloon, winch, boat.
4:Experimental Procedures and Operational Workflow:
BLIMP tethered to a boat, height controlled between 300-800 m, images taken every 5s. ZiviCat autonomously measured temperatures along predefined paths. Data synchronized via time matching.
5:5s. ZiviCat autonomously measured temperatures along predefined paths. Data synchronized via time matching.
Data Analysis Methods:
5. Data Analysis Methods: Image processing in MATLAB, including filtering (Gaussian or median), NUC, drift correction, feature matching, image stitching, and radiometric calibration using in situ data.
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