无人机拍摄参数与飞行姿态对夜间成像质量的影响评估

The impact of camera parameters and flight attitudes on UAV nighttime light image quality

  • 摘要: 夜光遥感是评估城市发展、分析人类活动强度以及监测光污染的重要手段。传统星载夜光遥感数据存在空间分辨率粗糙、过境时间单一等问题,无人机的高时空分辨率与可灵活部署等优势,使其成为获取夜光遥感数据的新手段。然而,由于夜间光照条件远低于日间,使得无人机夜间影像更容易受到飞行姿态与相机拍摄参数等外部因素的影响,准确评估无人机夜间成像质量对科学使用无人机夜光数据至关重要。为此,无参考空间域图像质量评估器被用来探究无人机拍摄参数、飞行高度和倾斜角度对其夜间成像质量的影响,进而确定无人机夜间成像的最优参数。结果表明,无人机夜间成像质量最佳拍摄参数为ISO 800和曝光时间1/15s,该参数组合下的图像噪声抑制、动态模糊控制及亮度平衡表现最佳。无人机在200至500米飞行高度均能采集高质量的成像质量,但倾斜角度对夜间成像的空间形变和亮度均会产生影响。图像形变情况会随着倾角的增加而线性加重,而倾斜角度的影像则更为复杂。倾斜角度的增加有利于采集建筑立面的夜光信息,但也会增加建筑物遮挡的风险,导致采集的夜光亮度变暗。总体而言,所得结果系统揭示了无人机夜间成像的影响机制,明确了最优无人机采集参数,为后续无人机夜间应用提供了丰富的理论基础与实操经验。

     

    Abstract: Objectives: Nighttime light (NTL) remote sensing is a unique optical observation technique for assessing urban development, analyzing human activity intensity, and monitoring light pollution. However, traditional satellite-based NTL data are constrained by coarse spatial resolution and limited temporal coverage due to fixed overpass time. In contrast, unmanned aerial vehicle (UAV), with their high spatiotemporal resolution and flexible deployment capabilities, offer a promising alternative for acquiring high-quality NTL imagery. Nevertheless, due to the significantly lower illumination at night compared to daytime, UAV NTL images are more susceptible to external factors such as camera settings and flight attitudes. Accurately evaluating the quality of UAV NTL imagery is therefore critical for ensuring the scientific validity of UAV NTL data. Methods: To comprehensively evaluate imaging quality, a series of controlled acquisitions focused on three primary dimensions: camera parameters, flight altitude, and tilt angle. Specifically, 24 combinations of ISO sensitivity (100 to 3200) and exposure time (1/15 s to 1/2 s) were tested at a constant f/2.8 aperture. Additionally, images were captured across seven flight altitudes (200 m to 500 m at 50 m intervals) and 13 tilt angles (0° to 60° at 5° intervals). Given the absence of reference images, the blind/referenceless image spatial quality evaluator (BRISQUE) algorithm was applied to quantitatively assess spatial image quality, with the goal of determining the optimal imaging configuration. Results: The results indicate that the best imaging quality was achieved with ISO 800 and an exposure time of 1/15 s, offering superior performance in noise suppression, motion blur control, and brightness balance. Flight altitude had a relatively minor impact on image quality within the 200 to 500 m. In contrast, tilt angle had a significant influence on both geometric distortion and image brightness. The geometric deformation increased approximately linearly with larger tilt angles, while the impact on brightness was more complex. Greater tilt angles improved the visibility of building facades but also introduced occlusion effects, leading to dimmer recorded brightness values. Conclusions: The result systematically analyzed the mechanisms affecting UAV NTL imaging quality and identified optimal acquisition parameters, providing a theoretical insight for future UAV NTL remote sensing applications.

     

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