How to scan large objects with high accuracy?
3D scanning large objects with high accuracy can be a difficult task. A 3D scan of a large object can be made up of millions of points of data and aligning that data with inspection level accuracy is the biggest challenge. During scanning large sized object, you could run into what is known as a cumulative error. This would cause the scan to misalign which in turn makes the scan data useless. On the other side of the same coin we have photogrammetry. Photogrammetry uses cameras to capture the 3D shape and data of an object. Its key strength is that it is easy to apply to large objects including entire vehicles, buildings, giant sculptures, terrain, and more. Where it falls short is in reference to the accuracy of the scans it provides. The data is not accurate enough for reverse engineering, let alone industrial level inspection. So how can we solve this problem? The SHINING 3D Digimetric Photogrammetry combines general high accuracy for large-scale object measurement of photogrammetry and the high resolution of handheld laser scanning all in one solution. This makes it the ideal tool to partner up with SHINING 3D’s FreeScan line of handheld laser scanners to tackle large-scale projects that require high end specifications.
The Digimetric Photogrammetry System uses a camera and markers to create a 3D reference of an object. From there the data can be imported directly into SHINING 3D’s FreeScan software and uploaded as a global reference file. This creates a reference of the scanned object within the software which tells the FreeScan the shape and size of the object it is scanning. Scanning with the reference file opened is equivalent to coloring in an image in a coloring book; the data is all there, just the details need to be filled in. This approach allows the scanner to eliminate cumulative error and provide an accurate large-scale scan of difficult to scan large objects; the measurement accuracy could reach to 0.01mm+0.01mm/m. Since the size of the object is already used as a reference in the scan data, the scanner fills out the remaining data with ease and without fear of misalignment. The finished scan possesses all of the details of a handheld scan while retaining the scale of the object obtained in photogrammetry. This allows the use of the scan data in high-end inspection and reverse engineering applications.
SHINING 3D recently had the chance to work on a project for a customer that needed to obtain the complete scan data of a prototype touring car so they could design the interior of the vehicle to their required specifications. They required the high-level accuracy but the size of the vehicle in question was too large to retain the accuracy tolerances they required. The team decided to do the scan using the FreeScan series handheld laser 3D scanner together with Digimetric Photogrammetry System.
The first step was to place the large encoded markers on the objects surface area. These markers are identified by the Digimetric’s software and allow for the creation of the surface area. A large reference bar is laid against the object to help the software recognize the size of the object. Once setup is complete, multiple pictures are taken from all angles to create the reference data. The software pieces together the images one by one to create a total image of the object. Once enough information is generated the file is saved and exported. The Digimetric’s markers are removed from the object and the team begins placing the smaller markers for the FreeScan.
Using the FreeScan’s software the photogrammetry data is imported as a global reference file. From there the scanning begins. Since the scanner is “filling in” the data of the scan the process is quick and easy. The reference removes the possibility of misalignment so the scan job can be completed in a shorter amount than it would if the reference data wasn’t in place. The engineers scanned the vehicle in a matter of minutes. Once the scan is completed the file can be meshed and converted into an STL file which can be used in CAD software to reverse engineer the scan data and begin the design process. The scan process and the completed scans are shown in the images below.
The Digimetric Photogrammetry System allows you to scan objects deemed too big for handheld laser scanners all while retaining their ease of use, speed, accuracy, and level of detail. Whether scanning complete vehicles, turbines, statues, or other large-scale objects, the Digimetric Photogrammetry System and FreeScan series have got you covered.
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