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How to overcome the challenges of planning a 3D laser reading campaign? actuality

How to overcome the challenges of planning a 3D laser reading campaign?

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How to overcome the challenges of planning a 3D laser reading campaign?

The laser statement transforms surveying in terms of design, construction and visualization. The applications supported by laser digitization, such as the scan-to-bim, require that the data of the point cloud is of sufficient quality in terms of precision or density of points.

The elimination of human errors on a project is essential to obtain quality results, reducing waiting times and minimizing costly errors. The intelligent planning of a statement is the key to an effective and precise scanning process.

The basics of a site plan

in order to obtain the data you need, you need to plan your statement. Even if you are considering assemble your points clouds without using a target. You must always determine the number of scans you need and Where to make them, to obtain sufficient coverage. Minimizing this figure is essential to maximize the efficiency of time, and this reduces your need to potentially create a site grid (we will come back to this point).

Digitization planning allows you to define Optimal statement stations while meeting the specific quality and precision requirements of this particular work. Taking time to plan guarantees that you have the most recent version and that building contact details are calculated properly.

Your site plan will mainly provide three results:

  1. The number of scans to be carried out.
  2. If the statement must be made in color or not.
  3. The possible difficulties. For example, limited access to areas to be raised.

site planning takes time. It is therefore essential that the data of the site is acquired in the most effective way with the minimum of possible scans. Here are some tips to put yourself on the right track.

Step 1: Plan time for planning  

The preparation is vital. The creation of a good site plan and a relevant lifting control grid is fundamental for any 3D laser / modeling project. Make sure you have allocated enough time to visit and understand the site by good people, the development of the site's plan and the generation of a site's reference control grid.  

At this stage, also think of how you will capture the information useful for your project. Avoid paper at all costs. Use mobile applications (tablet, PC) to note where you should place your scans and targets on site. You can easily develop your survey plan when you move to a room, and download a hand -drawn sketch or even a 2D floor plan for greater precision in order to position your passage points.

Although you have mobilized your team for your survey campaign, you must also mobilize people to develop the site plan. These employees will have to know how to use your scanners. They will also have to plan the order in which you are going to scan the site.

Step 2: Plan your scanning course and minimize the number of scannings  

Laser scanners take measures thanks to a straight laser beam. Thus, a room with a lot of pillars, small corridors and other obstacles that are difficult to cover will require much more digitalization to cover than a larger but empty room. You must also take into account the level of details you need and what you want to do with your point cloud. Nothing beats an in -depth visit to the site, but a set of 2D plans and photos can do the job.

If you follow an assembly method based on the use of targets, you must consider where You will place your targets. If you use a target registration method, you should make sure that there is enough overlap between scans to obtain a precise alignment. Depending on the software you use and the environmental uniformity you scan, there will be a hole of 30% to 50% required to assemble your scans with precision.

your first objective in planning A digitization course must be to ensure that you obtain total coverage of the area. But you also want to try to minimize the number of scans to be carried out. Basically, if you can make fewer scans to get full coverage, the entire process will be more effective. The reduction in the scans number that you must achieve not only reduced the time spent on site, accelerates the registration process and obliges you to collect less data, but can also eliminate the need to create a site grid. This brings us directly to the next stage.

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Step 3: Minimize errors  

The use of different scanners leads to propagation errors which are limitations inherent in the scanner which have aggravated when they are Combined.

For a cloud of composite points, scans are effectively built on each other, all rooted in one and the same "home" scan. The more steps between a given scan and its "home" scan, the more propagation error. They can be minimized, but can never be eliminated.

a critical step in the planning of the site is to decide whether the total number of scans that you will have to produce to obtain total coverage of the area will create & nbsp ; propagation errors.

uncertainty increases on the basis of the following equation: (n1 * 2) 2 + (n2 * 2) 2 ... = (total error) [where "n" is the error rate for each scan].  

So, if you have a scan error of +/- 1 mm, it will worsen at +/- 4 mm for each scan Deleted from the “Home” scan. If this number of propagation errors exceeds the project parameters - you will have to create a site grid, also known as a set of "noted control points" or "control network".

A site grid is a set of fixed targets in an area, each with a known relative location measured with precision using a total station. Total stations are capable of making more precise measurements than 3D laser scanners.

by completing your site plan and capturing the statement control points, you can match your checkpoints to the cloud points during the recording process. This is a key step in the process of creating a precise point cloud, whether or not you use targets to record your 3D scans.

by being judicious in the number of scans That you create, you can potentially eliminate the need to create a site grid. Depending on the type of project you start, you can choose not to deal with a site grid, but you will need to make sure you get the accuracy you need for your project.  

Step 4: The overall process  

time being money, the use of latest generation scanners like the PX-80 allows you to make important savings. In the field, digitization without target saves time by avoiding the target placement and makes it possible to digitize larger projects faster. But you can waste this time saving later in the workflow if you do a bad cloud alignment, or if you need excessive scanning overlap to ensure a good recording.  

All point cloud recording software does not easily integrate the control points transmitted by the site plan to those generated by the point cloud. You will also need less overlap between scans and therefore, you will reduce the number of scans to be made in the field.  

during treatment, you can then create several "Home" scans, in Creating "scans trees" up to the precision requirements of projects and by further reducing propagation errors. Using efficient processing software, you take the best party from registration without a target and provide a rationalized and effective process to align your scans.

the impact of good site planning  

3D digitization is recognized for its precision, reliability, speed and ease of use. The exceptional adaptability and flexibility of 3D scanners make them ideal to measure all types of environment in all types of activity sectors. This confidence must be maintained by ensuring good planning and preparation.

commercially speaking, on -site visits and the use of devices must be reduced to a minimum. By creating precise site plans and associated control points, site planning costs are more than covered by facilitating scanning without target and optimizing the recording and treatment of high quality points clouds.  

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