结合了快速形态调查的测深量和激光雷达数据

作者：Sam Pfeifle

As it arrives at the state line separating Washington from Idaho, the Snake River forks, one tine flowing to the south as the Snake along the border, the other heading due east as the beginning of the Clearwater. Anyone traveling east on a boat would quickly encounter the Clearwater Memorial Bridge, a roughly 228-metre-long bridge dedicated to veterans of WWII.

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,将近70年后其若干uction began, the Idaho Department of Transportation entrusted a pair of engineering companies with creating a full topographic survey of the bridge and surrounding area as part of a multiyear project to replace it and surrounding roadways, ensuring safe and efficient transportation for generations to come.

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.”

He knew that adding multibeam sonar data to the mobile mapping cloud data would give the resulting topo consistent, fine-grained, accurate data from the river bottom on up, but there was a problem: Horrocks doesn’t have a multibeam sonar unit.

奥尔森说：“在犹他州，我们没有任何大河流，大多数湖泊不需要太多的测深数据。”“我们通常只是做单束声纳，这不是我们在这里想要的。”

Luckily,Spicer Grouphas 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：两个mobile sensor platform for its above- and below-waterline mobile mapping, the same mobile scanning platform Horrocks invested in 18 months prior for its roadway mapping.

Olson decided to reach out to Spicer project surveyor Nathan Shepherd and combine forces on the job—the first time he’d ever subcontracted out to another surveying team.

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Done in a Day

Horrocks would drive the bridge and surrounding roadways. 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.

Because the Pegasus is a sensor platform capable of ingesting data from multiple sources, the multibeam and lidar information could be integrated into a single point cloud.

牧羊人说：“飞马座的山被螺栓固定在船上。

Shepherd解释说，虽然Pegasus的LiDar单元只需在桥下和河岸沿着河岸的一个来回抓住一切，但Multibeam更像是割草。该团队在多束中需要40或50次通过，以获取河流的底部以及所有清除率高和液压研究所需的数据。

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，大量节省了时间。

“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。

因此，大约有三分之一的时间，” Shepherd总结说，“而且我不知道数据多了几百倍。”

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.”

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Mobile Mapping’s Back-office Effect

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工程师已经进行了激光扫描大约八年了，但大约18个月前就购买了Mobile Scanning，购买了Pegasus：Hexagon一部分Leica Geosystems的两个平台。bob体育报道Horrocks的校长和调查经理Lonnie Olson说，这绝对影响了他的劳动力。

“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.”

They also recruited recent graduates from local geomatics programs and started training them as soon as they were on board to work with mobile point-cloud data.

“现在我们有一个5人的团队,”奥尔森说,“who do nothing but extract data from point clouds all day, every day.”

Leica Geosystems’ Jason Ellis said Horrocks’ experience is typical, and the movement of field staff into the back office should be seen as a smart move and not a conciliation.

“The continuity from the field to the office is always a challenge,” Ellis said. “It’s hard to convey what’s been done in the field and how it needs to be processed.”

By having experienced field staff cross-trained into experts at working with the data, you have people who can intuit what the field staffers were trying to accomplish as they sort out the important data.

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.

“I see a lot of people doing post-processing in the field so they know they’re good and can pack everything up or know they need to rescan if they’ve had an issue,” he said. “A lot of field people are starting to take on the role of analysis, and that’s a good thing. You’ve got sharper people in the field who can be that much more productive.”

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.

“Your standard CAD machine handles this stuff just fine,” Olson said. “The software is starting to catch up now. You don’t really need much to get going. It’s pretty simple. Even your basic laptop can handle it. Sure, you need a decent computer, but we’re an engineering firm, so we had them anyway.”

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A Seamless Workflow

在Pegasus Manager中完成的所有后处理后，工作流程对于将数据集组合起来很简单。运行两辆车的团队都能够实时检查数据和图像以进行覆盖范围，然后使用轨迹调整模块将所有数据汇总在一起并限制调查控制。Pegasus软件使用自动化功能提取和其他自动化功能来使后处理快速有效。

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’ Jason Ellis provided technical support on the job, as he’s been doing for survey teams for decades. Even he was impressed by the speed of collection in this case.

Thanks to their complementary expertise, expectation management and good communication, the two engineering firms partnered for success. Given strong communication ahead of time and relatively smooth operations, the teams were able to combine bathymetry and lidar data without a headache.

A full version of this article was published inxyHt magazinein Oct. 2019.