How does the scanner work?
3D laser scanning is a process involving the use of high speed lasers that fire at incredibly high rates of speed. There are two different types of scanners that are commonly used: Phase-based and Time of Flight.
Phase-based scanners utilize a constant beam of laser energy that is emitted from the scanner. The change of phase of the laser light is measured to allow the scanner to calculate a distance. The advantage to this type of scan is a higher point capture (currently up to 2,000,000 points per second.) The downside is that it has a much shorter range (currently about 30 meters.)
Time of Flight scanners use a pulse of light that is emitted from the scanner. The time it takes for the pulse to travel from the scanner to the object and back is measured, allowing the scanner to calculate the distance. The key benefit to this type of scanner is longer range scanning. The downside is that they do not collect as many points (currently up to 50,000 points per second.)
Typically, phase-based technology is used inside and time of flight is used outside, though the best practice is to use both to get the most precise and accurate scans.
What makes up the image on the screen?
The image is created from a “point cloud,” which contains millions of points that can be measured precisely including the distances and elevations between the points.
How accurate are the measurements?
The closer and more scans taken, the more accurate the scan, but typically scans are between 1/4 and 3/8 of an inch.
How are scans colored?
A high resolution digital camera takes a series of seven photographs that are then registered together and then again to the point cloud to produce the colored points.
Can you view the photography?
Yes. Using free software called TrueView™ you can view and manipulate the color photos on top of the scan to make basic measurements that you can then e-mail to other offices, investigators and agencies.
How do you create a 3D image?
The accident site or crime scene is scanned from multiple sides, and then all of the scans are geometrically joined to create a unified point cloud of the site.
How do you establish the coordinate system?
We run control with GPS units or tie into an existing local datum when preferable.
Are scan measurements as good as regular survey points?
Yes, but the 3D laser scan has the advantage of the point cloud and photo. The biggest advantage is the number of points you collect scanning, which then become survey notes.
How big are the files?
A raw scan file can be as big as several gigabytes. Once the points are processed, the scans registered together, and a senior CAD technician collects the points in the scan that represent the environment being surveyed, the resulting data can be converted to AutoCAD® drawings. This brings down the file size dramatically (typically 10-15 megabytes.)
How close are the scan points?
Scan points vary from 1/4-inch apart to as far away as you want. For highly detailed scans, we typically scan at 1/4-inch density.
Does that mean that you have a point every quarter of an inch?
What products can you get from one scan?
One scan can be used to produce point clouds, digital color photos, survey-quality files, or 3D computer models. You also can produce videos from the scans of multiples views and insert animation or virtual buildings, roads, people, etc. to show proposed areas.
What type of software can you export into?
We export into AutoCAD®, MicroStation, Revit, and just about all types of common point register cad file programs. We can also export into Maya and Autodesk 3ds Max® modeling and animation software.
What type of files can you export from a scan?
LAS files and PTS file formats are becoming the most common way to transfer scan data
How does a CAD tech turn millions of points into a normal .dwg file or .dxf file?
By using all of the points and several different types of software, the CAD technician chooses specific points to draw a specific object. Then, the tech follows the points until the object is complete. There are now many types of software that turn scan data into drawings. However, none of them are automatic.
Is it possible for you to do the scans, register them, remove the noise, and deliver them to me so that I can put the points in the CAD file I choose?
Yes. We provide data to many different kinds of clients. Some want CAD files, while others prefer scan data or 3D models. We can provide all three.
What is noise?
Noise is when a moving object like a car or person walks through a scan. We can go through a process to remove all of those points that are not relevant. Noise is also created when using high speed data from phase-based scanners and must be removed.
How are the scans registered to each other?
We have a minimum of three targets in some scans and three targets from the previous scan. Another way to register scans is called “cloud to cloud,” where you use objects in the scan that appear in several scans (like a street light) that can be used like a target. This is less accurate, but much faster.
How far away can you scan?
We can scan from about one meter to approximately 300 meters with some of the new long range scanners. It depends on the accuracy you want.
How long does it take to scan an area?
Depending on the scanner, it typically takes five minutes for a good Phase-based scan and up to one hour for a high resolution Time of Flight scan.
Can you scan cars, boats and planes?
Yes. You can scan almost anything except water and other highly reflective surfaces.
What does a 3D scan cost?
It depends on the size, shape and locations. We can provide detailed quotes and ballpark numbers depending on your project.
Does a 3D scan cost more than a regular survey?
It depends on the complexity. On very simple projects, a regular survey will typically be cheaper. On intensive projects such as a major intersection crossing in a high commercial area, a 3D scan is typically cheaper.
Do you have to return to do additional surveying if we need to add an area that was scanned?
No. We can usually add the area from the original data. This greatly reduces returns and saves time on remobilization.
Can you tie scan data to other data?
Yes. We regularly tie scan data to aerial data, field-surveyed data, and photographic data.
How far can you travel?
Because we don’t require survey crews on the ground for weeks at a time, we can send scan crews to sites to collect the data, then tie it to GPS coordinates and come back and finish the project in our offices. This cuts down on travel costs and overall project time.
Is a scanner dangerous to the operators or the eyes of the public?
No. 3D laser scanners are safe for both operators and the public.