News & Events
New Service for Rental Scanners
True North | Spring 2020
Image 1: Cory, our technician in Toronto, preparing a scanner for On-Site Compensation
Since the fall of 2019, Cansel’s rental department has utilised FARO’s on-site compensation routine for all outgoing rental scanners and in-house serviced scanners for a much-improved customer experience when renting a scanner. It is important to note that this is a routine that all users of FARO’s S series scanners can and should utilize.
3D laser scanners, unlike most surveying equipment, do not have apparent knobs and screws to be tweaked and manipulated. However, like all high-precision surveying equipment they are subject to deviation from published accuracies due to improper handling and extended normal usage.
During the manufacturing and service of FARO scanners in FARO’s facilities, every scanner is checked thoroughly. During this time certain parameters are measured and stored in the scanner. In the end, the scanner’s performance is represented on a factory-issued accuracy certificate that comes with that particular scanner.
As time goes by these parameters will change and hence they should be checked and adjusted. This is why FARO recommends an annual calibration process, through which appropriate calibration and compensation parameters are returned to factory precision.
Parting with the equipment for the purposes of calibrating the scanner in the midst of a project is not an option for most customers so the ability to perform on-site compensation is a huge benefit.
FARO’s innovative “on-site compensation” is embedded in the processing software, i.e FARO SCENE, at no extra cost. This feature allows the users to perform a vital part of the calibration on their own. This functionality is present in all FARO S series scanners.
As shown in image 1, the process involves attaching 5-6 special targets in a vertical pattern and the use of the internal compensation application in FARO SCENE. The software controls the scanners through WiFi and will direct the user to follow a few simple steps like aligning the scanner to one of the targets. Upon termination of measurements/scan, the software will present the errors and finally give the user the option to apply the compensation values to the scanner (image2).
Image 2: A PDF report among other files informs the user of existing error and how much the process can improve the errors.
To understand the implications, one should note that 3D laser scanners are very similar to robotic Total Stations. They measure distances and horizontal and vertical angles to obtain the point cloud. Intensity readings of the returning laser and photos taken by the built-in camera are all stitched together. As such, a Black and white intensity map and a coloured point cloud is obtained.
Image 3: 3 main axes of scanner that should be perpendicular to each other
For practical reasons, points are then converted to a Cartesian coordinate system in the form of x, y and z from their original form of measured distances and angles. For these calculations it is assumed that the “turning axes” of polar coordinate systems are orthogonal to each other”, which is not necessarily true (image3).
If you have ever seen Cansel’s service department you have seen the technicians working around pillars with collimators on top. The main operation of these collimators is to remove these imperfections or, “collimation errors.” Needless to say, if such a misalignment is not appropriately compensated for, then calculating the Cartesian coordinates would result in incorrect coordinates.
In most state-of-the-art surveying equipment and scanners, there are routines installed on board to facilitate the “compensation” of the error instead of traditional “calibration” or physical tweaking of hardware. This has put the power of compensation in the user’s hands which saves a lot of time and money.
This new service will benefit the clients renting 3D laser scanners as well as those customers who own FARO’s S series scanners. Interested parties should contact Cansel’s technical support team if they want to perform the on-site compensation on their own.
It is noteworthy to mention that Cansel also provides our clients with several maintenance programs for factory-level calibration and compensation which involves free-of-charge replacement scanners while the work is being performed. Please contact our sales team for further information.
Peter Afshar
Geospatial Systems Specialist – Professional Services (Training & Technical Support).