空气扫描技术的改善提高了生产力

作者：琳达·达菲（Linda Duffy）

通过改进的扫描功能和功能，满足了对空中激光雷达的需求增加，这些功能在更少的时间内会在较大的区域上产生密集的点云。As an early adopter of scanning technology, Woolpert, the fastest-growing architecture, engineering and geospatial (AEG) firm in the US, has owned and operated every product in Leica Geosystems’ LiDAR series since the ALS40 was released in 2002. Woolpert purchased its first Leica TerrainMapper in early 2019 and has since acquired three more. Today, the TerrainMapper is Woolpert’s preferred technology for large area mapping and difficult terrain, including Department of Transportation (DOT) projects and federal programs such as the United States Geological Survey (USGS) 3D Elevation Program (3DEP).

Demand for elevation data

Aerial LiDAR data is a valuable source of information for many applications, such as 3D urban modelling, infrastructure development, coastal and natural hazard monitoring, and environmental conservation. Efforts are underway to establish a current national LiDAR dataset, and there are numerous local and regional entities investing in LiDAR coverage as well.

Expectations for density and accuracy continue to rise to match the enhanced capabilities of LiDAR sensors. Incremental improvements in performance culminated in the release of the Leica TerrainMapper, a linear-mode sensor that allows very dense point clouds to be collected at a higher altitude, greatly reducing acquisition time.

伍尔珀特（Woolpert）的副总裁兼地理空间部门负责人约瑟夫·塞普（Joseph Seppi）说：“有了大面积的映射，效率确实会得到回报。”“我们的项目可以超过30,000平方英里，甚至超过100,000平方英里，因此能够以更快的速度飞行的能力使TerrainMapper成为非常有效的选择。”

The TerrainMapper is capable of collecting LiDAR at flying heights between 300 metres (m) and 5,500 m and delivers USGS LiDAR Quality Level 0 (QL0) data at flying heights up to 2 kilometres (km). This outstanding level of efficiency is ideal for larger regional or national mapping projects where operating costs have a major impact on the frequency of updates.

Meeting and exceeding the specs

每个项目都有最低数据要求，具体取决于预期的应用程序。例如，USGS QL1数据必须至少为每平方米至少8点（PPSM），其均方根误差（RMSE）不超过10.0厘米（CM）。其他标准可能包括叶子，没有雪，没有积水和没有雨。在温带气候中，落叶树和雪是障碍。在热带和亚热带气候中，云和雨水通常是一个问题。由于许多地理区域中的挑战性条件，在有限的飞行窗户上收集有效的数据对于完成工作至关重要。

In 2019, the Wyoming Department of Transportation (WYDOT) contracted with Woolpert to map three landslide areas along a 10-mile stretch of the Continental Divide in northwest Wyoming, close to Yellowstone National Park. Woolpert collected LiDAR at 50 ppsm and colourised the point cloud with imagery collected simultaneously with the integrated Leica RCD30 aerial camera. The final digital terrain models (DTMs) and triangulated irregular network (TIN) models provided WYDOT with a baseline to determine the slide movement, volume and rate at which the earth is moving over time. WYDOT performed an independent check and compared over 120 individual point cloud elevations from field collected points. The average elevation difference of 3.6 cm exceeded the requested 5 cm vertical accuracy.

The TerrainMapper has also proven effective on linear utility projects and powerline rights-of-way and successfully measures sag on elevated power lines. Even while flying faster and higher than other sensors, the TerrainMapper returns the necessary point density for a variety of projects.

“In high relief terrain we achieve greater efficiency by flying higher without adjusting to as many different altitudes,” Seppi stated. “And for utility work, it is safer to fly at a high altitude far above the lines, with the added benefit of capturing more of the surrounding area.”

Woolpert also flew more than 10 USGS projects in various states in 2019 with the TerrainMapper. In states like Florida and Ohio, the large volume collection at high speeds was instrumental in completing mapping projects within one flying season, despite the weather conditions.

“The weather in some places can be challenging, leaving us with fewer days to work, so the high-volume collection capability of the TerrainMapper helps us finish the project quickly and maintain consistency,” Seppi continued. “Also, the point distribution, patterns and excellent intensity returns from this sensor are extremely beneficial for many feature extraction uses.”

这张放大的轮廓地图显示了在风河湖附近的路面，管道和涵洞等特征。

Acquisition and processing integration

The post-processing workflow is another area where efficiency impacts overall project costs. Woolpert uses the Leica HxMap multi-sensor processing platform, which is designed to streamline the handling of TerrainMapper data. HxMap processes, calibrates, and registers LiDAR point clouds while simultaneously processing image sensor data and colourising the point cloud. With help from HxMap, Woolpert delivers fully processed classified point clouds that meet strict project specifications for accuracy and density.

Seppi说：“ HXMAP使我们能够更加敏捷，并随时适应变化。”“当我们有关键的截止日期时，我们可以轻松地转移处理以从其他项目分配HXMAP资源。HXMAP就像一个黑匣子，它会自动在幕后执行其作品。”

Designed specifically to work with TerrainMapper data, HxMap leverages the advantages of the integrated scanner/camera system to generate all airborne data products within one single interface. HxMap offers embedded aerial triangulation and a solution for large oblique imaging projects, country-wide orthophoto projects, and large or small LiDAR projects.

怀俄明州交通运输部将伍尔珀特提供的LiDAR数据转化为各种图形，包括Wind River Lake附近该地区的数字地形模型。

Continuous improvement

The Leica TerrainMapper is the next generation of LiDAR sensors after the highly successful ALS80 series. The sensor system increases data collection rate versus flying height, improves flight planning, and achieves even point distribution. The enhanced productivity saves time and money, while the higher pulse rate, greater laser power and gateless technology contributes to higher point density.

“Leica Geosystems sensors just keep getting better,” Seppi says. “The performance jump to TerrainMapper from ALS80 was significant. We find the circular scan pattern has a lot of advantages, such as line-to-line calibration and adjustment for pitch. Flying higher and faster boosts our efficiency 200-400%. Leica Geosystems products have been the backbone of our sensor fleet since 1989.”

Demand for 3D LiDAR data is on the rise, which makes timely acquisition and processing increasingly important. The tight integration of TerrainMapper with the HxMap workflow expedites the entire process, from data download to product generation, to support faster turnaround on every mapping project.