Combining bathymetry and lidar data for a fast-turnaround topographic survey

Case study

Author: Sam Pfeifle

当它到达州线,将华盛顿与爱达荷州分隔开来时,蛇河叉,一个tine流向南部,沿边界的蛇流向南部,另一个尖端作为蛇的开始。任何乘船向东行驶的人都会迅速遇到Clearwater Memorial Bridge,这是一座大约228米长的桥梁,专用于第二次世界大战的退伍军人。

The bridge, opened in the spring of 1951, was designated ‘functionally obsolete’ by the federal government more than a decade ago, largely because of the roads that feed it, which are no longer suited to the traffic the bridge handles daily.

2019年3月,即建造建造近70年后,爱达荷州交通运输部委托一对工程公司,对桥梁及周边地区进行了完整的地形调查,作为一个多年项目的一部分,以取代其和周围的道路,以确保几代人的安全有效运输。

这项工作首先Horrocks Engineers,在整个美国西部设有15个办事处,其中包括爱达荷州的三个办事处。Horrocks的校长和调查经理Lonnie Olson说,收集桥梁和周围道路的调查数据是其移动地图部门的标准工作,但该项目还要求为河底和桥梁子结构提供测深数据。

“They wanted a look at the scour around the bridge pilings,” Olson said. “One of the avenues they’re looking at is to keep the substructure and much of the bridge itself.”

他知道,在移动映射云数据中添加多层声纳数据将使最终的TOPO一致,细粒度,准确的数据从河流底部开始,但存在一个问题:Horrocks没有一个多层声纳单元。

“In Utah, we don’t have any big rivers, and most of the lakes don’t require much bathymetric data,” Olson said. “We normally just do single-beam sonar, which isn’t what we were looking for here.”

Luckily,Spicer组has a multibeam unit for just this kind of bridge-scour analysis and hydraulic modelling. Even better, Spicer’s sonar vessel is also fitted with aLeica Pegasus:Two移动传感器平台用于其高于水线的移动映射,同一移动扫描平台Horrocks在其道路映射的前18个月投资了。

奥尔森(Olson)决定与Spicer项目测量师Nathan Shepherd接触,并在工作中结合了部队,这是他第一次将其分包给另一个测量团队。


Done in a Day



和周围的ro Horrocks将使桥梁adways. Spicer would drive the river to get everything below waterline, the riverbanks, and the underside of the bridge. Then they’d stitch the data together, extracting the planometrics to create a surface model and topographic survey.

由于Pegasus是一个能够从多个来源摄入数据的传感器平台,因此可以将多光束和LIDAR信息集成到单点云中。

“The mount for the Pegasus is bolted to the boat,” Shepherd said, “You can’t just go out and rent a boat and make it work.”

While the Pegasus’ lidar unit could grab everything with just a single pass back and forth under the bridge and along the riverbanks, the multibeam is a bit more like mowing the lawn, Shepherd explained. The team needed 40 or 50 passes with the multibeam to get the bottom of the river and the data necessary for all the clearance elevations and hydraulic study.

尽管如此,一切都在一天之内完成。

总而言之,大约花了三天的时间来建立工作的完整控制网络,然后在现场准备和进行实际扫描四天,总共在现场进行了7天 - 与传统方法相比,大量节省时间。

“Ten years ago,” said Olson, “you would have had to cross-section every 50 feet with a robotic total station and shoot in some key points of the structure, and you’d have to spend probably three to four weeks onsite doing control and collection.”

至于水下工作,“您可能每250英尺一次横截面,也许是单束声纳的总测量,然后是一个模型,” Shepherd说。“而且他们将无法获得搜查。没有办法知道这一点。他们本来不得不将潜水员送到视觉上看它。

So, it’s about one-third of the time,” Shepherd summarised, “and I don’t know how many hundreds of times more data.”

Even better? “When I pulled it all together,” said Olson, “our clouds lined up with a less-than-centimetre accuracy between Spicer’s and our upper and lower data. You would never find that kind of accuracy any other way. You could achieve it, but the cost would be exponential.”


移动映射的后台效果



您可能已经听过恐怖故事:“移动映射创建了很多数据,以至于无法管理!”“当您要做的就是驾驶扫描仪时,谁需要一个调查团队?”

Of course, it’s true that moving into mobile mapping is going to require back-office adjustments, but they should be relatively manageable if you prepare for them and offer training to your workforce.

Horrocks Engineers has been doing laser scanning for roughly eight years but just moved into mobile scanning about 18 months ago with the purchase of the Pegasus: Two platforms from Leica Geosystems, part of Hexagon. Horrocks’ principal and survey manager Lonnie Olson said it absolutely affected his workforce.

“Some of our field crews transitioned indoors,” he said. “And I have a team of former high-ranging CAD techs that we’ve trained to do survey work. We’ve been able to do most of the post-processing work in-house.”

他们还招募了本地地理学计划的近期毕业生,并在他们加入移动点云数据后立即开始培训。

奥尔森说:“现在我们有一个由五个人组成的团队,除了每天整天从点云中提取数据外什么都不做。”

Leica Geosystems的Jason Ellis说,Horrocks的经历是典型的,现场工作人员进入后台的运动应被视为明智的举动,而不是和解。

“现场办公室的连续性ways a challenge,” Ellis said. “It’s hard to convey what’s been done in the field and how it needs to be processed.”

通过经验丰富的现场人员交叉培训,可以与数据合作,您可以在整理重要数据时会直觉在现场工作人员试图完成的工作。

Similarly, said Ellis, it can be hugely helpful to have the people who are out in the field operating the scanners also able to work the software.

他说:“我看到很多人在现场进行后期处理,因此他们知道自己很好,可以打包一切,或者知道如果他们遇到问题,他们需要重新恢复。”“许多野外人员都开始扮演分析的角色,这是一件好事。您在该领域的人们的生产力要高得多。”

交叉训练还有助于填补地理空间专业的劳动差距。埃利斯说:“很难找到好人,因此,如果在该领域进行集合的团队可以管理大多数后处理,并达到可以认证的地步,这有助于保持项目的良好状态。”

As for the tech, Olson said there’s no need to stress about that. Just make sure you’ve got a lot of multi-terabyte USB drives, which are now extremely inexpensive, and don’t go cheap on your hardware.

“您的标准CAD机器可以很好地处理这些东西,”奥尔森说。“该软件现在开始赶上。您真的不需要太多才能开始。很简单。即使您的基本笔记本电脑也可以处理。当然,您需要一台体面的计算机,但我们是一家工程公司,所以我们还是拥有它们。”


无缝工作流程



With all the post-processing done in Pegasus Manager, the workflow was straightforward for combining the datasets. Teams running both vehicles were able to check the data and imagery in real time for coverage, then use the trajectory adjustment module to bring all the data together and constrain for survey control. The Pegasus software uses automated feature extraction and other automated functions to make post-processing fast and efficient.

从那里开始,Horrocks能够将微观的文件和TopoDot文件传递到爱达荷州。(软件出口到所有通用行业标准格式。)

奥尔森说:“为了解决所有这些数据,四人组成的团队大约需要一周半的时间来提取完整​​的调查。”“它比几年前快得多。”

Leica Geosystems的Jason Ellis为这份工作提供了技术支持,因为他已经为调查团队做了数十年。在这种情况下,他也对收集速度印象深刻。



由于他们的互补专业知识,期望管理和良好的沟通,这两家工程公司取得了成功。鉴于提前进行良好的沟通和相对平稳的操作,团队能够在没有头痛的情况下将测深和激光雷达数据组合在一起。

本文的完整版本发表在xyHt magazine2019年10月。

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