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.

这座桥开业于1951年春季，被联邦政府指定为十多年前，主要是因为养活了它的道路，这些道路不再适合每天处理桥梁的交通。

In March of 2019, almost 70 years after its construction 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.

这份工作fell first toHorrocks Engineers, which has 15 offices throughout the western United States, including three in Idaho. Collecting survey data for the bridge and surrounding roadways was a standard job for their mobile mapping unit, said Lonnie Olson, principal and survey manager at Horrocks, but the project also called for bathymetric data for the river bottom and bridge substructure.

奥尔森说：“他们想看看桥桩周围的冲刷。”“他们正在寻找的途径之一是保持子结构和大部分桥梁本身。”

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。”

幸运的是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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一天完成

恐怖将驱动桥梁和周围的道路。Spicer会驱车河流以将所有东西放在水线，河岸和桥梁的下面。然后，他们将数据拼接在一起，提取平面计算学以创建表面模型和地形调查。

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。

Still, it was all done in a day.

All told, it took about three days to set up the full control network for the job, then four days onsite preparing and doing the actual scanning, for a total of seven days in the field— significant time savings compared to traditional methods.

“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.”

至于在水下工作,“你可能有cross-section every 250 feet, maybe a dozen total measurements with single-beam sonar, and then a model from that,” said Shepherd. “And they wouldn’t have been able to get the scour. There would be no way to know about that. They would have had to send divers down to visually look at it.

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

You’ve probably heard the horror stories: “Mobile mapping creates so much data it’s impossible to manage!” “Who needs a survey team when all you have to do is drive a scanner around?”

当然，搬进移动映射的确需要后台调整，但是如果您为他们做准备并为您的员工提供培训，它们应该相对易于管理。

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。亚搏苹果appHorrocks的校长和调查经理Lonnie Olson说，这绝对影响了他的劳动力。

他说：“我们的一些现场工作人员在室内过渡。”“而且我有一支由前高级CAD技术组成的团队，我们已经训练过进行调查工作。我们已经能够在内部完成大多数后处理工作。”

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.

“Now we have a team of five people,” Olson said, “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.

同样，埃利斯说，让在现场操作扫描仪的人也能够使用该软件，这可能非常有帮助。

“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.”

Cross-training also helps fill the labour gap in the geospatial profession. “It’s hard to find good people, so if the team doing the collection in the field can manage the majority of the post-processing and get to the point where it can be certified, that helps keep projects on track,” Ellis said.

至于这项技术，奥尔森说，无需对此强调。只要确保您拥有很多多端的USB驱动器，这些驱动器现在非常便宜，并且在硬件上也不便宜。

“你的标准CAD机器处理这些东西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。

From there, Horrocks was able to deliver the MicroStation and TopoDOT files to the Idaho DoT. (The software exports to all common industry standard formats.)

“To crunch all that data, it was about a week and a half for a team of four people to extract the full survey,” said Olson. “It’s a lot faster than it was a few years ago.”

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.