Exploring the surface below water

In September 2014, Leading Edge Geomatics (LEG) working together with staff from the Nova Scotia Community College (NSCC) and the Applied Geomatics Research Group (AGRG), installed the Airborne Hydrography AB (AHAB) Chiroptera II system, used for near shore environmental monitoring, into the Beechcraft King Air 90C aircraft in order to perform the team’s first ever point clouds using a topobathymetric system. A leading topographic LIDAR and aerial photo collection company with projects throughout North America, LEG decided to put its extensive operational and data processing expertise into using this new LIDAR scanning system, anticipating new markets and research in shallow water environments. It is hoped that this new sensor will lead the way in this area.

任何曾经尝试在加拿大大西洋地区进行空中调查的人都会意识到，连续两天的无云状况非常罕见。即使鉴于该系统旨在以400m（1300 ft）获取数据的高度低，我们也不希望像我们一样快速地进行此初始项目。幸运的是，最初的航班是在一系列不寻常的晴天，晴天的背对背系列中推出的，其中一些最好的飞行天气都可以记住。除了由于水柱中的泥泞沉积物而必须回忆的一些区域，我们还可以在不到一周的时间内收集我们所有的优先项目。由于Chiroptera II系统非常友好且易于学习，因此该团队能够在捕获数据的同时通过培训来运行多个操作员，并且所有这些都报告了直观，易于操作的界面。该系统允许操作员分析飞行收集过程中采样的波形，以确定是否记录了淹没的地面。这使运营商能够迅速做出决定，不仅可以节省宝贵的飞行时间和费用，还可以保证许多飞行任务的成功。

该处理软件由Ahab（称为LIDAR Survey Studio（LSS））提供，可在仍在飞机中时查看扫描结果。在使用了其他几个比赛的LiDAR数据处理应用程序之后，该团队发现LSS能够轻松配置，处理和输出最终数据。该软件将飞行路径与原始波形一起使用的任何跨度（Sychronized Postion态度导航）进行处理，并将其以直观且布置良好的接口呈现。处理参数是通过配置文件设置的系统设置，处理设置（分类方法）和校准（传感器未对准）。软件处理的结果提供了定位且完全分类的数据。然后，用户检查与水面相关的底部命中量的处理数据，以确定分类是否成功。如果需要进行一些修改，则进行更改，并再次通过软件运行数据，直到分类正确地表示数据为止。产生校准，正确定位和分类数据集是一个非常直接的过程。

完整的3 d视图显示的点快速和smoothly, allowing the user to examine the processed results easily and work on the data to represent it as needed. The tools for display provide countless ways to represent the results. Selecting an individual return, or point from the data, displays the corresponding waveform data and image. These views aid in determining the accuracy of the data classification. The only limitation is the lack of manual classification tools. It would be useful to be able to change the classification of points based on the wealth of data contained in the full waveform and the rapidly available QC images (images that analyse the quality of the data). In practice, this may make it easier to understand if a return is in fact a bottom hit or submerged vegetation, instead of doing the classification clean-up in a third party application without access to the waveform information.

The Chiroptera II is a well-built, solid solution for shallow water collection. Our team was able to achieve excellent penetration results, but as expected, the system is heavily dependent on good water clarity. Areas such as the St John River would immediately block return data when another stream of water enters the river. This is not unexpected and murky water will remain an obstacle to this system. However, in areas where the water clarity is acceptable, the system performs superbly. The inlets on the New Brunswick Northumberland shore yielded excellent results with almost all of the sea bottom mapped.

黑貂岛的数据显示，深度渗透到15米（49英尺）时的清晰度令人惊讶。地形扫描仪（作为Leica Ahab Dragoneye分别出售）在黑貂岛上与测深扫描仪隔离。该扫描仪在1,400米（4,600英尺）下的表现良好，并提供了比每米一分更好的地面采样。系统的多个外观角度确保数据中的LiDar阴影最小，这可能会消除对多个通过的需求。总体而言，Chiroptera II是一种非常有能力，灵活且设计良好的托托式 - 伴侣系统。

Written by Wayne Richardson