Flight Research Laboratory, Aerospace Research Centre, National Research Council Canada, 1920 Research Private, Ottawa, ON K1V 1J8, Canada.
Canadian Forest Service, Great Lakes Forestry Centre, 1219 Queen St. E., Sault Ste. Marie, ON P6A 2E5, Canada.
Sensors (Basel). 2021 Apr 27;21(9):3047. doi: 10.3390/s21093047.
The increase in annual wildfires in many areas of the world has triggered international efforts to deploy sensors on airborne and space platforms to map these events and understand their behaviour. During the summer of 2017, an airborne flight campaign acquired mid-wave infrared imagery over active wildfires in Northern Ontario, Canada. However, it suffered multiple position-based equipment issues, thus requiring a non-standard geocorrection methodology. This study presents the approach, which utilizes a two-step semi-automatic geocorrection process that outputs image mosaics from airborne infrared video input. The first step extracts individual video frames that are combined into orthoimages using an automatic image registration method. The second step involves the georeferencing of the imagery using pseudo-ground control points to a fixed coordinate systems. The output geocorrected datasets in units of radiance can then be used to derive fire products such as fire radiative power density (FRPD). Prior to the georeferencing process, the Root Mean Square Error (RMSE) associated with the imagery was greater than 200 m. After the georeferencing process was applied, an RMSE below 30 m was reported, and the computed FRPD estimations are within expected values across the literature. As such, this alternative geocorrection methodology successfully salvages an otherwise unusable dataset and can be adapted by other researchers that do not have access to accurate positional information for airborne infrared flight campaigns over wildfires.
世界各地的年度野火数量不断增加，促使国际社会努力在航空和空间平台上部署传感器，以绘制这些事件的地图并了解其行为。2017 年夏季，一次航空飞行任务在加拿大安大略省北部的活跃野火上空获取了中波红外图像。然而，该任务遭遇了多次基于位置的设备问题，因此需要采用非标准的地理校正方法。本研究提出了一种方法，该方法利用两步半自动地理校正过程，从航空红外视频输入中输出图像镶嵌图。第一步提取单独的视频帧，然后使用自动图像配准方法将其组合成正射图像。第二步涉及使用伪地面控制点将图像地理参考到固定坐标系中。然后，可以使用输出的经地理校正的辐射亮度单位数据集来派生火灾产品，例如火灾辐射功率密度（FRPD）。在地理参考处理之前，与图像相关的均方根误差（RMSE）大于 200 米。在应用地理参考处理之后，报告的 RMSE 低于 30 米，并且计算出的 FRPD 估计值在文献中的预期值范围内。因此，这种替代地理校正方法成功地挽救了原本无法使用的数据集，并且可以为其他没有准确的航空红外飞行任务的位置信息的研究人员所采用。
