Improvements in airborne scanning technology boost productivity

Author: Linda Duffy

Increased demand for aerial LiDAR is being met with improved scanning features and functionality that produce denser point clouds over larger areas in less time. 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.

对密度和准确性的期望不断提高，以符合激光雷达传感器的增强功能。在Leica TerrainMapper的释放中，性能的增量改进是一种线性模式传感器的释放，该传感器允许在较高高度收集非常密集的点云，从而大大减少了采集时间。

“With large area mapping, efficiency really pays off,” says Joseph Seppi, vice president and geospatial sector leader at Woolpert. “Our projects can exceed 30,000 square miles, even 100,000 square miles, so the ability to fly at a higher altitude at a faster speed makes TerrainMapper an extremely efficient option.”

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.

开会并超过规格

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.

TerrainMapper还被证明在线性公用事业项目和通行通行权方面有效，并成功地测量了高架电源线的下垂。即使飞行速度比其他传感器更高，地形室也返回各种项目的必要点密度。

“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.

塞皮继续说：“某些地方的天气可能具有挑战性，使我们的工作时间更少，因此TerrainMapper的大量收集能力有助于我们快速完成该项目并保持一致性。”“此外，该传感器的点分布，模式和出色的强度回报对许多特征提取用途非常有益。”

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

Acquisition and processing integration

后处理工作流程是效率影响整体项目成本的另一个领域。Woolpert使用Leica HXMAP多传感器处理平台，该平台旨在简化TerrainMapper数据的处理。HXMAP的过程，校准和注册发光点云，同时处理图像传感器数据并颜色点云。在HXMAP的帮助下，Woolpert提供了完全处理的分类点云，这些云符合严格的项目规格，以确保准确性和密度。

“HxMap allows us to be more agile and adapt on the fly to changes,” says Seppi. “We can easily shift processing around to allocate HxMap resources from other projects when we have a critical deadline. HxMap is like a black box that automatically performs its work behind the scenes.”

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.

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.

连续的提高

Leica TerrainMapper是在非常成功的ALS80系列之后的下一代激光雷达传感器。传感器系统提高数据收集速率与飞行高度，改善飞行计划，并实现偶数分布。增强的生产率节省了时间和金钱，而较高的脉搏率，更高的激光功率和无元技术则有助于更高的点密度。

塞皮说：“莉卡·地理系统的传感器一直在变得更好。”“从ALS80的TerrainMapper的表现跃升非常重要。我们发现圆形扫描模式具有很大的优势，例如线到线的校准和音高调整。飞行更高，更快地提高了我们的效率200-400％。自1989年以来，Leica Gebob综合app下载osystems产品一直是我们传感器机队的骨干。”

对3D激光雷达数据的需求正在上升，这使得及时获取和处理越来越重要。从数据下载到产品生成，TerrainMapper与HXMAP工作流程的紧密集成使整个过程都加快了整个过程，以支持每个映射项目的更快周转。