Scan Project Planning: Resolution & Scan Positions

The advances in laser scanning technology over the last five years have been impressive. Not only has the quality and quantity of the scan data we collect improved but also the size of the device and its ease of use. A while ago, a coworker of mine was commenting on how easy it was to use the FARO® Laser Scanner Focus3D.

While it is true that the operation of the FARO® Laser Scanner Focus3D has been simplified to the point where virtually anyone can be taught to operate the device, there are still challenges in successfully collecting data that will deliver the desired results.  This is what will be achieved during Scan Project Planning.

When planning a project you must first ask yourself what the final output from the project will be. Will you require 2D CAD drawings, 3D solid or surface models, a triangulated mesh, or perhaps just the point cloud itself. What level of detail will you require? The volume of point data required to create a simple 2D floor plan may be much different from the volume of point data required to 3D model the same space. Once you determine the final output, you can begin to plan the project.

To understand what settings will be appropriate to collect the necessary level of detail, you need to understand some scanner basics. Resolution is a term used to define the number of points collected in a single scan. The FARO® Focus3D can collect everything from 700K points all the way up to 700M in a single scan. The resolution selected will be based on two things: the level of detail required and the proximity to the object being scanned. As the scanner is operating, the spacing between the points being collected will increase with distance. This is due to the fact that the laser beams being emitted from the scanner diverge with distance. For example, if you are scanning a small area, such as an office, a lower resolution may be selected since the physical proximity of the scanner to the surfaces being scanned will be relatively short. Conversely, if you are outside scanning the facade of a building, a higher resolution would be required to obtain the same level of detail since the point spacing will become greater with distance.

The next thing to look at is how many scans you will require to capture the necessary detail. There are several factors that go into this estimation.

  • The scanner is a line of site device. The scanner has to “see” what you are trying to collect.
  • The level of detail required as determined by the project output. This will be determined by a combination of the scanners proximity to the object being scanned and the resolution setting. Let’s return to the example of scanning a typical office area. There may be a reception area, a hallway, and several offices. Being constrained by this environment, a lower resolution may be chosen due to the close proximity of the scanner relative to the surfaces being scanned. However, a large number of scan positions, a short distance apart, may be required so the scanner can “see” to capture the entirety of the offices, hallway, and reception area.  Conversely, scanning the facade of a building will likely require a higher resolution setting to maintain point density but spacing between scan positions can be maximized because of unobstructed site lines.
  • Finally, a useful object for planning scan positions is a layout drawing. This can be a detailed CAD drawing, a Google Map view, or even a simple hand drawn sketch. This will allow you to take a bird’s eye view of the job and plan your scan positions accordingly.

A final word of advice. Be prepared to be flexible once the project begins. Murphy’s Law is alive and well and living on your next scan site. The print you marked up with your scan positions may not have shown the trees growing near the facade you are trying to scan or the office area has been recently remodeled requiring you to reassess the quantity and location of your scan positions. It will happen, Mr. Murphy guarantees it.

Having an understanding of the steps required to plan your scan job will allow you to efficiently and effectively capture the right amount of point cloud data to successfully complete you project.

Good luck and Happy Scanning!

For more information about scan project planning, please complete the form below.

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By | 2018-02-20T02:50:45+00:00 May 21st, 2014|3D Documentation|0 Comments

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Kenneth Lyons

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