Scanning Tips

The following describes some tips for achieving an accurate scan.

Note: follow the tutorials on your NavVis VLX for information on optimizing point cloud capture and other scanning tips.

Walking Speed

Walk at a slow pace. This will help to ensure good quality.

• Moving too quickly may cause a low density Point cloud and blurry photos.

• Moving too quickly also degrades the quality in terms of accuracy and it increases the changes issues with SLAM. In particular you should avoid fast accelerations, rapid slow downs and sudden movements, abrupt stops or fast rotations. It is better to move slowly and with gentle, flowing continuous movements.

• When taking pictures, make sure you stand still without any motion, since motion blur cannot be compensated for. Do not rush, instead consider increasing the distance between pictures or capturing images only in one direction, while walking back without taking any.

Orientation

Keep the device as upright as possible while scanning. Tilting the device may result in your body being visible in the point cloud or photos. Avoid sudden or jerky movements.

Do not turn the device upside down while scanning.

Distance from Objects

The best quality images and point clouds are captured 1 - 10 m away from objects. No benefit is gained getting closer than 1 m to objects.

Use the Device Field of View (FOV)

Scan objects from many different perspectives for a more complete point cloud:

• Walk both up and down stairs.

• Walk in both directions through a corridor.

• Rotate 360° in corners and tight spaces.

• Walk around an object of interest multiple times.

• Rotate 90° to the left and right before going up or down stairs.

• Lift the device overhead to scan on top of or above objects, such as cabinets

• Crouch down to scan below objects, such as below window sills.

Small Rooms

Images captured in small and narrow spaces are prone to stitching errors, as walls and objects may be too close to be accurately captured. Try the following when scanning in small rooms:

• Scan the room from the outside by rotating 90° to the left and to the right in front of the room.

• Enter the room and rotate 360° to capture all of the environment.

Scanning Duration

In general the recommendation is to keep one dataset less than one hour long, the interface will remind you every 45 minutes and on the hour. Datasets of around 45 minutes are best considering alignment effort and post-processing duration.

Smaller datasets can be beneficial when a re-scanning plan is in place, where specific areas of a building need to be re-scanned at different time intervals, or if specific user permissions are distributed for viewing specific areas.

Scanning Outdoors

• Use loop closures and keep them smaller than you think is necessary. In an outdoor situation they "feel" smaller than they actually are. Check the quality map for the executed loop sizes.

• Build your scan from left to right based on loops.

• Walking and turn especially slow. Naturally, people tend to speed up outdoors and underestimate the distances they are walking.

• If you notice feature-less areas during planning, you can artificially enrich them with objects. Move cars or boxes to add structures to your mapping space or open doors and windows in different ways to create differentiation points.

Do Not Scan in the Rain

The NavVis VLX is protected against dripping water. However, do not scan with it in the rain. If water gets on the camera lenses and the laser scanners, the scanning results will be affected.

If water gets on the NavVis VLX, follow these steps:

1. Stop the scanning and shut it off.

2. Move to a sheltered location out of the rain and use a clean and dry microfiber cloth to wipe all water from the camera lenses, laser scanners, and device housing.

3. If you want to continue scanning, start a new dataset.

4. Before you pack the NavVis VLX, dry it thoroughly using a clean and dry microfiber cloth. Make sure water has not entered the device in the folded position.

Dusty Environments

The NavVis VLX is protected against dust during operation.

If you scan in an environment with a lot of dust, the air intake and outlet vents on the NavVis VLX prevent dust from entering the device:

• The air intake vents have filters that keep dust out.

• The air outlet vents constantly blow air, which keeps dust out.

If dust gets on the camera lenses and the laser scanners, the scanning results will be affected. Follow these recommendations:

• While you scan, pause regularly and check for dust on the camera lenses and laser scanners.

• If required, clean them and the NavVis VLX following the procedures in the Maintenance section.

Operating in high temperatures

We do not recommend using NavVis VLX to map in areas where temperatures fall outside the range of 5° to 35° Celsius (41° to 95° Fahrenheit), as well as in humid areas. The temperature range is determined by the built-in components of NavVis VLX, such as the cameras or PC. If exposed to excessive heat, the integrated cooling system will be overloaded and other components like the CPU will not operate at their full capacity to save the device from overheating. This can ultimately lead to performance issues like lagging live SLAM or even broken datasets.

Scanning in dark areas like a factory 

Some projects need to be scanned in environments where there are dark areas - there is just not enough daylight or artificial light sources present. While the human eye can adapt to minimal light, your NavVis VLX is limited by technical constraints. What can you do to overcome these contraints?

Warning: Make sure when scanning in darkened areas to take appropriate precautions. Take care where steps and wet surfaces may not be obvious.

There are three options to choose from, when scanning dark areas:

• Scan the building as is - no extra light sources: With limited lighting, panoramas and point cloud coloring will be negatively impacted. Both are based on the pictures taken by the cameras during scanning. If no or only a very little amount of photons reach the camera sensors, the result is just technically limited. If your project is not reliant on coloring, you can still scan.

  We would recommend to skip coloring of the point cloud during post-processing, which will then contain intensity values from the lidar measurements instead. You can achieve that by:

  • Cloud Processing: When processing data in the Cloud, you can deselect the point cloud coloring. You can find help on this in Point Cloud Settings.

  • Desktop Processing Software: When processing on a local Ubuntu workstation or server, use the additional flag in SiteMaker or Ubuntu terminal --no-color-cloud. You can find the options for that here in our documentation on Adding Custom Arguments.

• Add a light source to the device: This option is not recommended as it interferes with the sensors that implement the field-of-view of the device and invalidates the device’s warranty or subscription contract.

• Add additional lights to the environment: (Recommended). Additional light sources will be necessary for the full area covered in one scanning session. When planning the lighting follow these rules:

  • Place floodlights before starting to scan.

  • The floodlights must not be triggered by movement but be permanently on.

  • Do not carry the floodlights around within one scanning session.

If these rules are not followed the lighting changes will be visible both in the coloring (mix of bright and dark, because you captured the same area in both conditions) and the point cloud itself, due to the movements and changed objects. Overall, with limited light sources, the coloring of point cloud and panoramas will be much less than perfect.