大数据对测量师来说是一个大问题吗？

Laser scanning has made data acquisition substantially simpler but the accurate analysis and registration of data requires both effective software and the core skills of the land surveyor. Is the software doing the job and is it encouraging those without the core skills to have a go? GW has discussed the subject with several surveyors with wide experience of laser scanning.

一段时间以来，全世界一直对大数据感到兴奋，这能够挖掘公司收集的大量数据并将其整合在一起推断出来的能力。188asia备用网址。。天哪知道什么。几乎可以肯定的是，那些想向我们出售一些我们不需要的东西的人和我们从未听说过的公司的电子邮件的脚本脚本过的人的刺激性电话的原因。188asia备用网址更积极的是，大数据有望在天文学和基因组学等领域的重大进展。

对于“ Mega”，请阅读“ Giga”

但是，测量在大数据方面有自己的问题。它们与未经请求的营销有所不同。我们的大数据问题来自高分辨率激光扫描和成像，并且通过将扫描拼接在一起以制造复合点云，3D模型和马赛克而加剧。

对于测量师来说，从涉及使用总站或手动方法进行相对较少的现场观察的测量技术转变为涉及使用激光扫描仪收集数百万个观测值的技术，这是一个令人生畏的前景。即使使用传统技术，管理原始数据，计算数据和结果的挑战也是一个可以轻松重新审视的方式。通过激光扫描，我们即使在小型项目中都在研究数据的千兆字节。但是有些项目可以轻松地要求进行数百次扫描。硬件和软件是否符合此问题，如果没有，需要解决哪些问题？

用户的视图

根据特许测量师Michael Gallie＆Partners的帕特里克·柯林斯（Patrick Collins）的说法，激光扫描仪供应商推荐的软件包都不擅长处理包含数百张扫描的大型数据集。单个扫描的文件大小存在局限性，并且该软件在合并扫描方面的速度很慢，因此，小时（或更长时间）的速度很慢，而您的高端64位巨型PC则可以通过千兆内的RAM GRINDS来传递。此外，可用的软件无法处理从收集到分析到可交付的完整调查过程，需要中介格式，其中丢失了重要的元数据，例如扫描名称，目标位置和控制信息。

‘They’re also not very good at overlaying’, says Collins, ‘to the point where, when you attempt an overlay, the model collapses’. He adds, ‘One might expect, as new versions appear, that these problems would gradually go away but instead menu options are changed and you find you can’t do what you previously did. Processes which worked in a previous version of the software suddenly no longer work after so-called upgrades.’

柯林斯继续说：“所有这些都可能导致对模型的整体准确性缺乏信心，因为扫描被合并并覆盖。简而言之，这些包装的一些设计师似乎不知道测量的基本原则以及维持尺寸准确性，校准和控制的需求。在3D软件中使用全球坐标的问题存在持续的问题，其中一位市场领导者目前正在处理一个错误，其中重新调整了点云的整体规模，从而导致了对现实世界数据的微小但重要的更改。”

BIM的解决方案？

With the recent push towards all things BIM, and the clever placement of laser scanning as a solution to BIM as-built data acquisition, Collins finds that his company is seeing increasing demand for “laser scan surveys” unrelated to the actual client requirement. ‘We’ve long been a profession eager to use new technology and demonstrate it to clients to show them what it can offer (whether they need it or not!). Many of us are also rather ingenious at putting together systems of sensors and computers. Alas none of this is of much interest to clients. Once a surveyor has ascertained exactly what it is his client wants surveyed, at what scale, accuracy and the end purpose of the survey, then it should be up to the surveyor to decide whether he uses a tape or an airborne or terrestrial laser scanner or an imaging system.’

许多特许测量师，他们使用扫描进行测量和区域参考调查面对不合格或兼职测量师的竞争，他们购买或租用了扫描仪并提供服务，但没有基本的调查知识。最糟糕的是，它们只是黑匣子，纽扣式操作员。这些问题对专业并不陌生。过去，我们去过EDM和GPS。当这些革命性的技术出现时，总是有那些热衷于利用它们的技术，但在不了解调查工作的基本原理的情况下。柯林斯引用了一家主要的超市连锁店，最近任命了这样的公司。客户留下了数百次未参考的扫描，没有控制权，并且仅在一个项目上，尺寸变化高达2.5米。

Who Needs Control?

关于大型数据集的注册，柯林斯从一家客户的制造商那里听到了能够注册700次扫描但没有调查控制的客户。他观察到：“我们的经验表明，您将在大小的数据集中获得“漂移”，尤其是高度，这正是经验丰富的测量师所期望的。最终，没有调查控制的700次扫描的注册提供了无法证实的结果，不能被视为调查，但是有一个缺乏经验的扫描仪用户群，他们将接受其软件包中的绿灯，因为它们是正确的！”

Laser scanning has made data acquisition substantially simpler but the accurate analysis and registration of data still requires the core skills of the land surveyor. The lack of understanding of “good” data (accurate, repeatable, reliable) is not just a problem for non-surveyors but extends into the software. Not only does much of the current offering fail to establish and maintain a proper control/registration structure but it also does not offer proper management of the data throughout the life-cycle of the project, through maintaining unique scan names, scan targets, co-ordinates and change management.

正如人们所期望的那样，通过已建立的测量设备制造商从整体到零件的数据出售的处理软件 - 作为测量师结构数据，但没有其背后的测量师，将控制和细节视为相同的软件。如果人们忽略了调查的原则，就可以得到答案，并迅速（因此是竞争性的），但这并不强大。

数据 - 多长时间？

Turning to the question of long-term storage of laser-scanned big data, the first crucial question is what data has to be kept, why and for how long. Why, is a fairly straightforward question to answer. It has to be kept in case the survey is called into question in the future. Contracts normally stipulate five years or a bit longer. For that period, it has to be possible for any surveyor to follow the process used by the original surveyor from fieldwork through to products. For the raw data, this could mean not only recording the data in a suitable format and possibly imagery as well, but also the location and orientation of the scanner, date and time of observation and so on.

该过程的下一个阶段是一起注册扫描并添加调查控制。这涉及记录控制位置，注册计算的结果和统一点云数据。在这一点上，如果需要点云作为可交付的可交付，则测量师必须在数据清除过程中从数据集中删除虚假点。到了这个阶段，测量师可能具有原始格式，预注册和编辑数据的三组重复数据，所有这些数据必须保留，直到注册的复合点云被验证为准确和完整为止。

通常，客户端可交付是2D图或3D矢量模型。这是测量师可能需要将复合点云数据转换为另一种格式的点，以便能够选择用于定义边缘和表面的激光扫描点。测量师可能会使用软件工具来识别某些功能和手动技术来完成调查。结果是一个小得多的文件，但是验船师必须考虑如何建模表面，而这永远不会是真正平坦的，出于客户的目的。此信息还必须根据需要记录并呈现给客户。

What we have is a huge amount of data in various formats with only parts of the process maintaining required survey information. This makes it difficult, if not impossible, to preserve any reasonable sort of traditional survey audit control.

The second question is: what should you do with this vast quantity of data after the retention period? This is a commercial decision although there may be legal implications. The surveyor has to decide its value (or potential value) and, if he decides to retain it, what information has to be retained with the point cloud and modelled outputs to give future potential users confidence of its quality. With a 100 scan project likely to reach 50Gb between various versions and formats. Data retention is neither simple nor cheap.

这并不那么简单！

从这个讨论可以得出两个主要结论sion. Firstly, professional surveyors tend to use a number of different processing packages because there is not as yet a single piece of software that can act as a one-stop shop. This multiplies the task of data management and demands that interfaces are robust, otherwise data and metadata gets lost in translation. The situation has become exacerbated as laser scanning is used for larger and more demanding projects with ever bigger datasets.

Secondly, there needs to be a common understanding between scanner suppliers, surveyors and clients, that laser scanning involves more than pushing a button. This is a surveying instrument and, like any other surveying instrument, its use should follow good survey practice both in the field and especially when processing the data in the office. Salesmen should be emphasising the issues regarding data processing to their customers. Surveyors should understand and follow good survey practice. Clients should appreciate that this is the way to achieve good quality reliable data. By employing ‘surveyors’ who do not follow good practice, clients increase the risk of receiving poor quality data and the associated costs when it is put to use. Ignorance of this should be no excuse.

This article was published in Geomatics World January/February 2015

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致谢

这篇文章以午餐的聊天开始生活，并从那里升级了！感谢Pat Collins，Ian Coddington，Stuart Robson，Jan Boehm，Paul Burrows等人的贡献和评论。