【3D Scanning Knowledge】What is 3D Scanning Accuracy? - SHINING 3D Scanner Buying Guide
When discussing 3D scanners, a frequently mentioned concept is 3D scanning accuracy. How do you understand the concept of 3D scanning accuracy? What are the differences between accuracy, precision, and volumetric accuracy? If you are confused by these professional 3D scanning terms, then this article is for you!
Simply put, the most common 3D scanning terms are:
【3D Scanning Efficiency】 - This affects the "speed of the scanning process"
• Point Distance
• Frame Rate (FPS)
• Field of View (FOV)
• Object Size
【3D Scanning Accuracy】 - This affects the "error between 3D object and actual object" and "quality of scanned object"
• Accuracy
• Precision
• Volumetric Accuracy
This article will discuss "error between 3D object and actual object" and "quality of scanned object." (For information on "3D scanning efficiency or speed," please refer to: 【3D Scanning Knowledge】4 Tips to Improve 3D Scanning Efficiency!)
Accuracy vs. Precision vs. Volumetric Accuracy
When taking measurements, accuracy and precision must be considered as they indicate how close the measured value is to an accepted or established value. The International Organization for Standardization (ISO) refers to this as "Accuracy (Trueness and Precision) of measurement methods and results," defining accuracy as a combination of random and systematic errors. For applications such as automotive modification and industrial manufacturing, accurate data is extremely important.
Accuracy
Under certain measurement conditions, it refers to the degree of deviation of the estimated value from its true value during multiple measurements of a single instance, which can also be understood as "how close the measurement result is to the true value."
Precision
Under certain measurement conditions, it refers to the degree of dispersion among various measured values during multiple measurements of a single instance; "the lower the precision, the larger the standard deviation."
Source : SHINING 3D
Volumetric Accuracy
A formula derived from precise testing and calculations, which shows the error relationship between the measured value and the true value when the volume of the scanned model changes.
Most 3D scanner manufacturers also specify volumetric accuracy, which is the accuracy of several captures, and as the size of the scanned part increases, the global accuracy decreases.
For example: 0.05mm + 0.15mm/m.
Following the example, if your part is 2 meters long, the scanner's accuracy will be 0.05 + (0.15*2) = 0.35mm. This is a significant difference compared to the original single-scan accuracy! Therefore, especially if you are scanning large objects (e.g., a car), volumetric accuracy is more important than single-scan accuracy.
Source: Aniwaa
• Some 3D scanners with integrated photogrammetry modules can build a 3D framework before filling in the object with scanning markers. Markers serve as precise reference points for the 3D scanner, much like connecting the dots in a drawing, and by using the "framework" from photogrammetry, your data will be even more accurate.
• Photogrammetry is a 3D scanning technique that involves taking multiple photos of an object from different angles to calculate its shape and size.
Factors Affecting Measurement Accuracy
Regardless of manufacturer or market positioning, the accuracy of 3D scanners can fluctuate due to various factors such as temperature, data integrity, algorithms, and scan angle. Therefore, it is important to understand how to prevent accuracy deviations and obtain the most reliable and accurate 3D data.
1. Temperature
To ensure optimal scan accuracy, allowing the scanner to warm up and maintain a stable temperature is also key. Once the temperature stabilizes, calibration should be performed before scanning to achieve the best accuracy. The sequence of warm-up, temperature stabilization, calibration, and scanning will yield the most accurate results.
2. Data Integrity
Data integrity is an important factor affecting accuracy. Incomplete data can lead to inaccurate or distorted results, impacting the overall quality of 3D information. Therefore, it is essential to ensure the completeness and authenticity of data to obtain the most accurate results.
Incomplete Data
Complete Data
Complete Data
3. Algorithm
From calibration to data processing, algorithms play a crucial role in 3D data collection. It is a set of complex mathematical formulas that ensure the accurate reconstruction of scanned objects. Calibration is also an important part of this process, ensuring the accuracy of the scanner and providing the necessary data for the algorithm to function correctly.
4. Scan Angle
Ideally, the scanner should be positioned as perpendicular to the object as possible. This positioning helps the scanner extract markers more accurately, leading to more precise 3D data.
Scanning with FreeScan UE
The cumulative error of scanning larger objects will be greater. However, there are some scanning methods that can help reduce errors, such as "global markers" and "photogrammetry."
Global Markers
Before scanning the point cloud, we can first scan global markers, which allows the algorithm to optimize accuracy and obtain more precise data, ultimately improving volumetric accuracy.
Photogrammetry
Photogrammetry can improve the accuracy of global marker data. We can import an appropriate scale file and place matching scales near the object before scanning, depending on the object's size. Generally, photogrammetry is suitable for measuring large components in industrial applications that require high precision. Between these two methods, photogrammetry is considered superior to global markers.
Scanning an aircraft model using photogrammetry
Comparison Chart of Measurement Accuracy for SHINING 3D Metrology-grade 3D Scanner Family
For objects requiring high accuracy and small sizes, two models are recommended: AutoScan Inspec and OptimScan-5M Plus. Autoscan Inspec is fully automated and easier to use, while Optimscan-5M Plus can handle slightly larger objects than Autoscan Inspec.
High Accuracy and High Detail Applications
How should we choose from the FreeScan series? If the object we want to scan is large and requires high accuracy, we can choose the FreeScan UE Pro, as it is equipped with photogrammetry functionality, which can significantly reduce errors during the alignment process.
FreeScan UE 11 Application
FreeScan UE Pro Application
FreeScan UE Pro Application
Finally, let's talk about the FreeScan Trak. This scanner is different from others in that it does not require markers to be placed on the scanned object. If it is difficult to place markers on some large objects, this scanner can be considered.
Now that you are familiar with accuracy, precision, and volumetric accuracy, but still confused about SHINING 3D's scanners?
▶Click here to filter for suitable 3D scanner recommendations◀ (links to SHINING 3D's official website)
Many different terms often appear on manufacturers' websites and specification sheets. What truly matters are volumetric accuracy and mesh resolution, and how they meet your specific needs.
Although technical specifications for accuracy and resolution facilitate easy and quick comparison between different 3D scanners, they should not be the sole deciding factors. Factors such as brand certification, history, software, and after-sales service should also be considered.
If you are having difficulty choosing a 3D scanner, or are unsure what your company's specific case (and budget) actually requires?
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