Frequently asked questions

The principle of a phase-shift scanner involves the emission of a light ray at a specific frequency, and the recording of the reflection of this wave, which will be “shifted” or “displaced” by its impact on a reflective surface.
The displacement of the reflected wave allows the precise calculation of the distance between the point of impact and the scanner.
Phase-shift scanners are faster and more accurate than time-of-flight scanners.

The principle of a time-of-flight scanner involves the emission of a light pulse and the recording of the reflection time of this light pulse.
As the speed of light in air is known, the micro program of the device calculates the distance between the scanned surface and the scanner.
Time-of-flight scanners allow scanning over longer distances (up to 2 km) than phase-shift scanners (up to 80 meters).

No.
ATEX regulations on explosive atmospheres, which are in force on certain sites, do restrict the use of hazardous devices; at present, however, to the best of our knowledge, there is only one "ATEX" 3D scanner in the world, which was designed as part of a university research programme and is intended for use in a coal mine.
However, where site conditions require, our devices can be used subject to the acquisition of a “fire permit”.

A 3D scanner costs between 70,000 and 120,000 euros, depending upon the brand, the model concerned and its packaging (softwares, carrying case, etc.)

Possibly, but not from Urbica.

Every scanner has its strengths and weaknesses; it all depends upon the quality criteria considered: accuracy, speed, ease or use or maximum distance? The scanners chosen by Urbica have been selected on the basis of accuracy and speed; at present, they are the most advanced on the market (according to tests conducted by ourselves and confirmed in the laboratory).

Although a laser will always pose a potential hazard to the retina, the use of scanners in practice and their speed of measurement are such that this risk is virtually non-existent.
Standards are used for the classification of lasers by numerous factors, including their power. The lasers (Class 2 or 3R) used in 3D scanners are of the low power type, and do not require the use of any specific protective equipment.
However, it is inadvisable to stare at the laser with eyes wide open for a period of several minutes... given the speed of movement of the beam, this would be difficult in any case!

The origins of the "3D scanner operating by laser" have not been clearly established.
In the case of the laser itself, Albert Einstein was the first to describe the principle of stimulated emission in 1917, the basic principle for light amplification, or the “laser”.

A survey by lasergrammetry will incorporate three key stages.
Firstly, the marking-out of the entire structure to be scanned will allow the identification of the number of stations to be used, the potential positions of the 3D scanner, and the type and number of markers (flat targets or spheres) to be installed; the selection of hardware and the number of devices will be defined beforehand in conjunction with the technical proposal.
Scanning proper, or “3D laser scanning”, will then account for 80% of the project time on site. The objective is to obtain measurements or “points” over the entire surface of installations which are visible and accessible by laser. To this end, the operator will record multiple viewpoints with the device, just as a photographer would do for the documentation of an entire site.
Back at Urbica, operators will then integrate all the stations (assembly) in one and the same point cloud. In order to allow data processing tools to read these files with no loss of speed, the filtering of superfluous points (segmentation) or points which are very close together (sampling) is recommended.

Strong vibrations, movements, smoke, fog, frost and snow, temperatures exceeding 60°C, fine dust, distance (no less than 1 metre) and paints, the wavelength of which in the visible spectrum is very close to that of the laser.

Using our phase-shift scanners (Trimble FX), a shot, a "station" or a "scan" will generally take between 5 and 10 minutes, depending upon the grid size (resolution) selected.
Using the time-of-flight scanner (Trimble GS200), the time taken to record a shot will generally range from 20 minutes to 2 hours...

A number of shots will be required to complete a project. An installation can be surveyed by the simultaneous use of a number of scanners, thereby reducing the overall time spent on site.

No, not in the case of the scanners selected by Urbica. However, some existing scanners can or must be mounted on a stand.

Yes. 3D laser scans can be supplemented by conventional topographical surveys. In some cases, this may be a necessary means of enhancing the accuracy achieved over an entire site.
A theodolite used for a topographical survey can improve the assembly of shots recorded by laser scanners.

A theodolite will ensure the accuracy of large-scale dimensional surveys. A theodolite may also be necessary for the plotting of coordinates from files in an existing system, in order to establish the flatness or verticality of the structure surveyed.

This depends upon the scanner: Phase-shift scanners of the Trimble-FX type are powered by a 16 V battery, which is the size of an external hard drive, providing an independent power supply for half a day. The GS200 time-of-flight scanner requires a 220 V d.c. power supply or, failing this, can be used with a generator.

Yes. The new generation of laser beams used in 3D scanners are not affected by either darkness or daylight. Consequently, it is possible to scan in the dark (at night time, at the bottom of a cave, a tunnel, a tank or a building) or in the daytime.

No. The wavelength of the laser lies within the visible spectrum – this means that it is only possible to measure what the human eye can see. Likewise, the laser cannot measure effectively through water, glass or smoke, as the laser beam will be subject to light diffraction as it passes through these materials.

Yes. Rain will not affect the quality of measurements, although the clean-up of point clouds will require greater care, in order to eliminate any droplets which might have been scanned. It is essential that hardware should be protected, and that sealed IT devices should be used. That being said, some of our scanners are fully-sealed, and can be used in the rain for hours.

Targets and spheres provide a useful means for the assembly of cloud points obtained from different viewpoints in a single file. These benchmarks must remain immobile throughout the scanning progress, thereby maintaining their coordinates and remaining identifiable in the point clouds generated from various stations.

Naturally, it is possible to scan a small object. However, an object of small dimensions will probably require sub-millimetric precision. In practice, our devices are not designed for this level of accuracy. Some companies complete scans of this type, using different measuring devices.

Not in the case of the scanners used by Urbica; scans require the complete immobility of the scanner and benchmarks. Some scanners (Trimble, Riegl) are suitable for this type of “dynamic scanning”, subject to other constraints such as accuracy, exhaustiveness, etc.

No. Although the laser can pass through these materials, the resulting measurement will not be reliable: diffraction of the laser beam will cause substantial inaccuracies of measurement.

Yes.
This is one of the genuine advantages of scanning by lasergrammetry: the device will allow the restriction of human intervention (manual surveying, scaffolding, contact with objects).
By the use of remote controls, laser scanning will also reduce the individual dosimetry of the operator (with the protection of ALARA scanning times).
However, the 3D scanner will still require meticulous protection, and the ventilation of the device should be inhibited.

Contact us to find out about our experience with operations in irradiated zones.

No, Urbica is not equipped for this type of measurement. The result obtained would represent the amplitude of movement of the scanned object. In general, "tracker" lasers are more suitable for this type of operation.

From -20°C to +60°C.

Yes. Some scanners (including our GS200 time-of-flight scanner) can capture measured objects in colour, while others can be used in combination with a digital camera.
However, this feature is of little benefit in industry or topography, and comes at a price.

Laser scanning undoubtedly has the following long-term benefits:

• the exhaustiveness of scans;
• the elimination of errors and omissions from scans;
• the generation of 3D files which are a faithful reflection of reality;
• the accuracy of files;
• speed of measurement;
• time-saving and the reduction of errors in engineering design analyses.

The drawbacks, which will lessen as future technological advances are introduced, are as follows:

• the slightly higher cost, in comparison with a manual survey;
• the size and weight of equipment;
• the size of the resulting files;
• the softwares required for the processing of point clouds.

Scans are completed exclusively by Urbica personnel. The two dedicated surveyors for 3D scanning operations are also responsible for conventional surveys (by theodolite or level) where necessary.

Urbica operates in all sectors of industry (see our web pages on services/industry), heritage management (architecture, civil engineering structures) and topography (surveys, volume measurements, DTM, etc.). Geographically, Urbica can operate in any humanly-accessible location, anywhere in the world.

In many cases, the urgency of scans is a decision-making criterion for Urbica clients. In some cases, Urbica will be able to respond on the same day; in general, Urbica will respond within 5 days following the confirmation of a job.

Scans are quantified on the basis of photos and plans submitted by the applicant; where possible, Urbica will undertake a site visit.
Once the environment and scope of the service have been evaluated, Urbica will prepare a quote which will incorporate the following: the time to be spent on-site, resources deployed, travel costs, the difficulty of scanning (on offshore or nuclear sites, and in terms of time schedules, dimensions, temperature, etc.) and the post-processing required in the office for the assembly of viewpoints and the delivery of the required file format.

Certainly! It generates no waste, consumes less energy than a conventional light bulb and, in certain cases, will allow the reduction of both travel and dosimetry (in a nuclear environment).

Yes, but only where 3D lasergrammetry technology is deployed for the application proper, in specific fields: façade and roofing plans, volume measurements, DTM, deviation or flatness controls, scanning of large interiors.

Yes: Contact us!

The 3D laser scanner will undertake the complete measurement of all the objects within its field of vision (360°), in the same way as a digital camera. There is no possibility of error on the part of the engineer.

A number of methods are available to ensure the quality and accuracy of a scan:

• Consultation of the setting and assembly reports supplied by the service provider
• Completion of counter-measures using conventional tools or methods
• Control of the coherence of the 3D model generated, by the superimposition of the point cloud
• Verification of the conformity of certain types of “catalogued” or “standardized” objects.

In order to verify the quality of a file generated by 3D scanning, Urbica can supply, prior to the provision of service, a sample file which is similar to that to be delivered upon the completion of the contract.
Upon the completion of service, the client is free to undertake their own quality control of our files (for structuring, exhaustiveness, accuracy, style identity) and to request the review of the latter.
For Urbica, more than anywhere else, the client is king!

Since 2007, Urbica has implemented a quality system of the type defined in ISO 9001, … although there has never been sufficient time to obtain certification to this effect.

A point cloud can be used for the following:

• The recording of dimensions between two items of equipment (clearance, ceiling clearance) or on the equipment itself (pipe diameter, door width, corner angles)
• The remote visualization of a site or structure (in case of a remote installation, intermittent opening, a site in service or which is difficult to access).
• Detection of non-conformities in a theoretical model (project) in relation to the actual situation represented by the point cloud (on an old site or a new site immediately prior to turnkey delivery)
• Simulation of the installation of new hardware (equipment, piping, extension) in an existing environment.
• The conduct of certain analyses associated with risk management (radioactivity, noise, explosion, run-off, retention capacity, etc.)
• Kinematics for the movement of heavy and/or cumbersome equipment on a crowded site (heaters in a nuclear power plant, etc.)
• There are many other potential applications... get in touch with us!

The raw file generated directly from the scan will have a “weight” of around 1 GB. The untreated point cloud produced from this file, which represents all the measurements recorded by the scanner, will comprise an average of 40 million points.
Following the assembly of scanner stations, a complete scanned site may consist of several billion points. As existing data processing tools cannot comfortably process information in these quantities, Urbica undertakes the sampling and decimation of points to produce files of approximately 100 MB.

For the reading of point clouds, the user must be equipped with the following, according to requirements: free viewer licences (Trimble, Leica, Pointools, etc.), fee-paying software licences for the installation of “fully-fledged” softwares for segmentation, sampling, measurement, modeling, exporting, saving of changes, etc.

Fee-paying licences for plug-ins to the main CAD tools (Autocad, PDS, PDMS, 3DS, Rhino), for segmentation, measurement, detection of collisions, exporting, saving of changes.

For the reading of model files: the most widespread computer-assisted design/computer-assisted drawing softwares: Autodesk, Bentley, Intergraph, Aveva, Dassault System products, etc. Free viewer licences (Trimble, Leica, Pointools, etc.)

For the comfortable processing of a point cloud, Urbica recommends a terminal equipped with the following, as a minimum requirement: a modern dual-core processor; 2 GB of live memory; 20 GB of available disk space; OpenGL 3D graphics card; 17-inch monitor. Naturally, ease of use will be substantially dependent upon the capacity of hardware used for the processing of these frequently large files.

Yes. The point cloud, as a faithful representation of the actual condition of an installation, can be compared with the theoretical model of the same installation for the detection of deviations, collisions and, in the majority of cases, the conformity of the model.

In principle, yes. In practice, your objectives will need to be analyzed for technical feasibility (point cloud quality, accuracy, density, exhaustiveness, source, etc.)

The point cloud, as a faithful representation of the actual condition of an installation, can be compared with the theoretical mode of the same installation for the detection of deviations, collisions and, in the majority of cases, the conformity of the model.