探索水下的表面

2014年9月，领先地理（Lead Edge Geomatics（Leg）与新斯科舍省社区学院（NSCC）和应用地理研究小组（AGRG）合作，安装了机载水文AB（AHAB）Chiroptera II系统，用于近海岸环境环境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.

Anyone who has ever attempted to fly aerial surveys in the Atlantic Region of Canada will realise that it is extremely rare to find two consecutive days of cloud-free conditions. Even given the low altitudes that the system is meant to acquire data at 400m (1300 ft), we were not expecting to move this initial project along as quickly as we did. Fortunately, the initial flights were launched during an unusual back-to-back series of sunny, clear days, with some of the best flying weather any of us could remember. With the exception of a few areas that had to be recollected due to muddy sediment in water columns, we were able to collect all of our priority projects in less than one week. Because the Chiroptera II system is so user-friendly and easy-to-learn, the team was able to run several operators through training while capturing the data, and all of them reported an intuitive, easy-to-operate interface. The system allows operators to analyse waveforms sampled during flight collections to determine if the submerged ground was being recorded. This enables operators to quickly make decisions that save not only precious flight time and expenses but also guarantees the success of many flight missions.

这个过程sing software provided by AHAB, known as LIDAR Survey Studio (LSS), enables viewing scanning results while still in the aircraft. Having used several other competitions’ LIDAR data processing applications, the team found LSS capable of easily configuring, processing, and outputing the final data. The software combines the flight path, processed with any SPAN (Sychronised Postion Attitude Navigation) with the raw waveform, and presents it in an intuitive and well laid-out interface. Processing parameters are set via configuration files for system settings, processing settings (classification method), and calibration (sensor misalignment). The results of the software processing provide positioned and fully classified data. The user then examines the processed data of the bottom hits in relation to the water surface to determine if the classification was successful. If some modifications are required, changes are made and the data is run through the software again until the classification represents the data properly. Producing calibrated, correctly positioned and classified datasets is a very straight forward process.

完整的3D视图快速，平稳地显示了点，使用户可以轻松检查处理的结果并根据需要进行数据表示。显示的工具提供了无数的表示结果的方法。选择单独的返回或从数据中指向，将显示相应的波形数据和图像。这些观点有助于确定数据分类的准确性。唯一的限制是缺乏手动分类工具。能够根据完整波形和快速可用的QC图像（分析数据质量的图像）更改点的分类将很有用。实际上，这可能会使您更容易理解退货是否实际上是底部命中率或淹没的植被，而不是在第三方应用程序中进行分类，而无需访问波形信息。

Chiroptera II是一种精心建造的，可用于浅水的固体解决方案。我们的团队能够取得出色的渗透率，但是正如预期的那样，该系统在很大程度上取决于良好的水清晰度。当另一批水进入河流时，诸如圣约翰河等地区将立即阻止返回数据。这不是出乎意料的，黑暗的水将仍然是该系统的障碍。但是，在可以接受水清晰度的区域，该系统的性能非常出色。新不伦瑞克省诺森伯兰海岸的入口在几乎所有海底绘制的地方都取得了出色的效果。

The Sable Island data showed surprising clarity at depth penetration to 15 metres (49 feet). The topographic scanner (sold separately as the Leica AHAB DragonEye) was tested on Sable Island in isolation from the bathymetric scanner. This scanner performed well at 1,400 metres (4,600 feet) and provided ground sampling at better than one point per metre. The multiple look angle of the system ensures minimal LIDAR shadows in the data, which could possibly eliminate the need for multiple passes. Overall, the Chiroptera II is an extremely capable, flexible and well-designed Topo-Bathymetric system.

Written by Wayne Richardson