Improvements in airborne scanning technology boost productivity

Author: 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).

海拔数据的需求

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。”

TerrainMapper能够在300米（M）至5,500 m之间的飞行高度上收集LiDAR，并在飞行高度达到2公里（km）处提供USGS LIDAR质量0（QL0）数据。这种出色的效率水平非常适合更大的区域或国家地图项目，在该项目中，运营成本对更新频率产生重大影响。

Meeting and exceeding the specs

Every project has minimum data requirements depending on the intended application. For example, USGS QL1 data must be at least 8 points per square metre (ppsm) with a Root Mean Square Error (RMSE) not exceeding 10.0 centimetres (cm). Other criteria may include leaf-off, no snow, no standing water, and no rain. In temperate climates, deciduous trees and snow are obstacles. In tropical and subtropical climates, clouds and rain are often a problem. Due to challenging conditions in many geographic areas, efficient data collection during limited flying windows is crucial for getting the job done.

2019年,怀俄明运输部(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.

林TerrainMapper也被证明有效ear 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.”

伍尔珀特（Woolpert）在2019年与TerrainMapper一起在各个州飞行了10多个USGS项目。在佛罗里达州和俄亥俄州等州，尽管天气状况，但高速批量的集合在一个飞行季节内完成了映射项目。

“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.”

This zoomed-in contour map shows features such as pavement, pipes, and a culvert near Wind River Lake.

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。”

HXMAP专为使用TerrainMapper数据而设计，它利用集成的扫描仪/相机系统的优点来生成一个单个接口中的所有空中数据产品。bob综合app下载HXMAP提供嵌入式空中三角剖分，并为大型倾斜成像项目，全国矫正项目以及大型或小型激光雷达项目提供解决方案。

The Wyoming Department of Transportation translated the lidar data provided by Woolpert into a variety of graphics, including a digital terrain model of the area near Wind River Lake.

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.