The evolution of LiDAR

Current airborne linear-mode LiDAR systems, such as the Leica Geosystems ALS series, capture 1 million points per second. Increasing the pulse repetition rate is the best way to achieve dense point clouds at lower costs, as the flying speed can be increased. The pulse frequency, however, is constrained by parameters such as energy consumption and eye safety. Single Photon LiDAR (SPL) technology enables a much higher pulse rate to be achieved, since much less energy is needed per pulse.

LIDAR系统通常由许多组件构建：

• 范围调查系统
• 扫描光学元件指导激光脉冲
• 一个位置和方向系统记录激光脉冲的起源点。

这些系统在每个发射的激光脉冲中使用相对较高的能量。每个脉冲都从飞机到地面传播，从那里反射回扫描仪。

通过使用更多的每个脉冲能量，可以记录更强的反射，因为飞机下方的地形会反射更多的光子。线性模式系统的输出令人印象深刻，这些系统提供具有高空间和辐射测量精度的数据。但是，该技术确实对可以实现的最大有效脉搏率施加了一些局限性。

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较高的脉搏率

The pulse repetition rate is an important parameter to define the acceptable flying height and flying speed during data acquisition. A higher pulse repetition rate allows for faster flying while maintaining a similar point density.

随着线性振荡系统的脉搏速率的增加，电力消耗也会增加。此外，使用的激光器将产生更大的热量。

脉搏率更高的脉搏率所需的越来越高的平均光输出能力是工程挑战。除了准确性和脉搏重复率外，传感器设计不仅需要考虑总电力消耗和系统冷却，还需要考虑大小，重量和眼睛安全。

为了迈出空中激光雷达系统开发的下一步，必须减少每个脉冲所需的能量。这可以通过更改范围调查系统的性质和技术来实现。包括SPL系统在内的下一代激光雷达技术依靠新的范围调查技术来实现较低的能耗和较高的脉搏率。

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从空间到地球

SPL技术最初开发地球satellite ranging and has proven to generate accurate range measurements using a minimal amount of laser energy in each pulse. Compared to currently available linear-mode LiDAR systems, SPL systems contain a laser splitter, which splits each laser pulse into an array of 10x10 small laser beams (beamlets). For these 100 beamlets, the travel time of the photons to the ground and back is measured individually. The addition of highly-sensitive photon detectors deployed within the SPL system enable detection of a single returning photon with much less required energy.

SPL系统每秒可以产生60,000个脉冲。由于每个脉冲分为100束，因此这会导致6.0 MHz的有效脉搏速率 - 明显高于线性模式激光拉尔（Linear Mode LiDAR）所能达到的。

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多个分数回报

线性模式LIDAR系统允许从完整返回波形内的各种目标反射中对峰进行注册，可以处理以检索多个返回。由于SPL系统不会捕获连续波，而是计算单个光子，因此无法使用这样的完整波形。但是，由于频道恢复时间为1.6纳米秒，仍然有可能检索多个回报。

This means that the photon counter is reset every 1.6 nanoseconds to count if any new photons return from the beamlet. These are then regarded as a new return. The result is a true multi-return LiDAR system with short inter-return separations of 24 centimetres. As a result, SPL systems can acquire high density point clouds of 12 to 30 points per square metre with many returns underneath canopies.

The point density varies inversely with the flying height. If the flying height is doubled, the covered swath will double, but the point density will be cut in half. An SPL instrument flying at 200 knots at 4,000 metres above ground will produce a point density of roughly 20 points per square metre.

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介绍the Leica SPL100

Linear-mode LiDAR remains the industry standard for airborne mapping, yet SPL technology is gaining acceptance for large projects. For instance, the U.S. Geological Service (USGS) 3D Elevation Program (3DEP), which aims to systematically collect enhanced elevation data in the form of high-quality LiDAR data, has explored SPL technology. The system has proven to meet the accuracy standard for USGS QL1 data, which corresponds to a height precision better than 10 cm for non-vegetated areas.

考虑到这一点，Leica Geosystems今年早些时候在Leica Spl100中引入了其首个市售的SPL空降系统。自2016年通过六角形收购以来，该公司机载产品组合中最新的传感器是第一个使用Sigma太空技术发布的传感器。亚搏苹果app

新的SPL100是新真人捕获解决方案的一半，即Real-Terrain。亚博ag真人规律与HXMAP（可扩展的后处理工作流软件）结合使用，新解决方案可以有效地收集和快速处理大面积LIDAR数据集。SPL100采集和HXMAP数据处理所获得的效率使更大，更频繁的LIDAR数据获取用于诸如密集的植被映射和变化检测等应用。

“ SPL技术最多是我们的飞行伙伴和客户的先前产品效率的10倍。现在有可能在大区域上提供极高的高点密度，从而使我们周围的世界数字化以前无法详细介绍。”约翰·韦尔特（John Welter），莉卡（Leica Geosystems）内容和工程服务和地理空间解决方案部总裁。“莱卡·雷特林（Leica Realterrain）是提供高质量的机载信息的下一个进化；既促进了该领域，又塑造了数字现实的未来。”

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The future of LiDAR

SPL technology continues to advance over time in terms of accuracy and radiometric capabilities. This will result in an expansion in application areas for which SPL technology is suitable.

It is also expected that the effective pulse rate of SPL systems will continue to improve, just as the effective pulse rate for linear-mode systems has steadily improved over the past two decades. With current performance levels at 6 million points per second, SPL systems could potentially be capturing 1 billion points per second in less than a decade.

通过更高的有效脉搏率来降低每点的成本是解决将来大区域高点项目的最佳方法。随着SPL技术在越来越多的应用中变得适当，我们将看到整个行业的积极变化，例如提高资源管理的效率，更有效的基础设施计划以及为自然灾害做好准备。

这个故事的一个版本首次出现在Gim International中。