At ASM DataCore, we’re proud to introduce a new high-accuracy large-format scanning service, purpose-built for the engineering, architectural, and surveying sectors. Using CCD-based scanner technology, we now offer digitisation of technical documents that demand geometric precision, dimensional fidelity, and archival-quality output.
This new service addresses a longstanding industry need: the accurate digital reproduction of physical drawings—even those that are aged, warped, or on fragile media—without distortion.
Why This Matters
Many organisations, especially those involved in infrastructure, utilities, transport, construction, and design, hold decades’ worth of large-format paper and Mylar documents. These originals:
- Were often created to scale.
- Have experienced material deformation over time.
- Are critical for retrospective design, compliance, or reverse engineering.
Until now, digitisation may have introduced errors due to inappropriate scanner technology. Traditional CIS (Contact Image Sensor) scanners, while affordable and compact, fail to reproduce precise dimensions and shapes—especially for large, curled, or delicate originals. This compromises accuracy, making them unsuitable for technical work where every millimetre matters.
The Right Technology for the Job: CCD Scanning
ASM DataCore now uses CCD (Charge-Coupled Device) large-format scanners, equipped with a camera-lens and mirror system to accurately digitise documents with high depth of field and geometric integrity. This is a critical upgrade in technology, especially for clients whose work depends on accurate measurements, proportions, and line fidelity.
Key Benefits of CCD Scanning:
| Feature | CCD Scanners | CIS Scanners |
| Depth of Field | Up to several millimetres (scans warped or curled documents) | None (document must be perfectly flat) |
| Geometric Accuracy | High – lens-based optics preserve scale and shape | Moderate to poor – distortion likely |
| Colour & Tonal Range | Superior for detailed lines and faded originals | Limited, especially with older media |
| Use Case Fit | Ideal for engineering plans, mylars, as-builts | Suitable for office documents only |
Digitising Process at ASM DataCore
Each document we digitise goes through our carefully controlled process, ensuring the highest possible fidelity:
- Preparation
- Drawings are unrolled/unfolded and laid flat on tables aligned with the scanner feed.
- Non-permanent measuring rulers are affixed to check input/output dimensions.
- Visual inspection of materials for warping, tears, or signs of aging.
- Scanning
- Scanning is performed at slow, controlled speeds to preserve geometry and avoid mechanical feed errors.
- Our CCD scanner captures full-width images using its depth tolerance to accommodate document imperfections.
- Verification
- Post-scan, we check key dimensions against the rulers captured in the image.
- The scanner is calibrated as needed to ensure output accuracy.
- Output
- Final images are delivered in high-resolution TIFF, PDF, or CAD-ready formats depending on your needs.
- Optional vectorisation or metadata tagging available.
Why Choose ASM DataCore for Large-Format Scanning
Digitising isn’t just about turning paper into pixels—it’s about preserving accuracy, enabling analysis, and preparing documents for CAD workflows, compliance, or future restoration. Our new CCD scanning service is ideal for:
- Old Mylar drawings or blueprints
- Survey maps and engineering schematics
- Construction plans or as-builts
- Documents used in legal, regulatory, or design-critical workflows
In environments where “drawn to scale” must mean “digitised to scale,” our technology and process ensure you get the precision you need.
Comparing Linear Array Large-Format Scanners and CCD Scanners for Engineering Applications
In the world of large-format scanning—used extensively for digitizing architectural drawings, engineering plans, and maps—two primary technologies dominate: linear array (or CIS, Contact Image Sensor) scanners and CCD (Charge-Coupled Device) scanners. While both serve the purpose of converting physical documents into digital formats, their internal mechanisms and output quality vary significantly, especially in terms of depth of field and geometric accuracy—critical factors for engineering and technical applications.
Linear Array (CIS) Scanners: Precision with Limitations
Linear array scanners use a row of sensors that sit in direct contact with the document being scanned. A typical CIS system has three RGB LEDs and sensor elements positioned directly beneath a transparent platen. As the scanner head moves across the page, it captures one line at a time. This contact scanning approach offers high resolution, energy efficiency, and compactness, making CIS scanners a cost-effective solution for basic document scanning tasks.
Key Limitations:
- No Depth of Field: The most significant drawback of linear array scanners is their lack of depth of field. Since the sensors are in immediate contact with the document, even minor variations in paper flatness—such as wrinkles, folds, or curled edges—can result in distortion or out-of-focus regions. Any object not flush with the scanner glass will appear blurred or misaligned.
- Inaccurate Geometric Representation in Raised Originals: When it comes to scanning media like blueprints, mylar drawings, or mounted engineering plans that might not lie perfectly flat, CIS scanners can introduce geometric distortions. This makes them unsuitable for precision-critical applications where the scanned dimensions must remain accurate to scale.
CCD Scanners: Optical Precision with Depth
Our CCD large format scanners utilize a digital camera-based system with a lens and mirror arrangement to capture an image of the document onto a CCD sensor array .This setup allows the device to optically capture the entire width of the scan path with high fidelity.
Advantages for Engineering Applications:
- Depth of Field: Unlike CIS scanners, CCD scanners possess a measurable depth of field—often several millimetres—which allows them to accurately scan documents that aren’t perfectly flat. This is crucial for delicate or older technical drawings that cannot be pressed down without risk of damage.
- True Optical Geometry: Because CCD scanners employ a lens system similar to that of a camera, they maintain correct geometrical proportions in the scanned image. This makes CCD scanners ideal for applications where scale, dimensional fidelity, and precise reproduction are required—such as as-built drawings, survey maps, or CAD originals.
- Colour and Tonal Accuracy: In addition to better geometric fidelity, CCD scanners also outperform CIS scanners in colour depth, tonal range, and handling of gradients, further enhancing the clarity and legibility of complex line work in technical documents.
Use Case Comparison
| Feature | Linear Array (CIS) Scanners | CCD Scanners |
| Depth of Field | Virtually none | Up to several millimetres |
| Geometric Accuracy | Only with completely flat originals | High, due to lens-based capture |
| Image Quality | Moderate; flat documents only | High; handles curves and texture |
| Ideal For | Office documents, flat blueprints | Engineering plans, maps, old/damaged media |
| Price Point | Lower | Higher |
Accurate Reproduction of Geometrically Precise Documents Requires Special Consideration
When dealing with technical drawings, engineering plans, or architectural documents—particularly those intended to be “to scale”—the need for faithful reproduction becomes paramount. Even slight distortions introduced during scanning can render a document inaccurate for measurement, analysis, or reverse engineering. Below are multiple critical factors that must be considered to ensure geometrical accuracy:
Considerations
Aging and Deformation of Original Materials
Older documents, especially those 60 years or more in age, were often created on polyester-based film (such as Mylar) or other early plastic substrates. These materials were selected for their durability, but:
- Over time, they are subject to dimensional changes due to temperature fluctuations, humidity, and material fatigue.
- Even when such deformation is not visually apparent, the material may have shrunk, stretched, or warped slightly.
- As a result, the original dimensions may no longer match the intended design, which introduces invisible but critical deviations from true scale.
This underscores the importance of using a scanning system that preserves existing geometry as precisely as possible without introducing new distortions.
Limitations of Linear Array (CIS) Scanners for Long or Warped Documents
Linear array scanners, commonly found in roll-fed large-format scanners, scan documents line by line as they move past a fixed sensor array. While effective for flat and uniform originals, this method can introduce multiple forms of distortion:
- Stretching or compression artifacts may arise over long documents, especially when scanning at higher speeds or when the document is not perfectly flat.
- Skew or bowing errors can result from mechanical feed inconsistencies, roller slippage, or slight wrinkles in the media.
- The lack of depth of field in linear scanners amplifies these issues, as any deviation from perfect contact with the scanner glass leads to out-of-focus or distorted lines.
Due to these factors, CIS-based scanners are not suitable for high-precision geometric reproduction, particularly during long scanning paths.
Impact of Scanning Speed on Geometric Fidelity
The speed at which a document is scanned also plays a significant role in image fidelity:
- Faster scanning speeds, while convenient, increase the likelihood of introducing feed errors and motion-induced distortions.
- Slower, high-precision scanning allows for more stable mechanical operation, improved synchronization, and reduced vibrations or warping during the scan process.
Thus, slower is better when scanning documents that require high geometric fidelity—especially large or delicate originals.
CCD Scanners Provide Superior Geometric Accuracy
To mitigate the issues above, CCD-based scanners should be used whenever dimensional accuracy and geometrical integrity are critical:
- CCD scanners use a camera with a lens and mirror system, which allows the scanner to view the entire width of the document optically.
- This setup provides depth of field, allowing for accurate capture even when the document is slightly curled, wrinkled, or mounted on uneven surfaces.
- The lens-based system preserves true geometric proportions, reducing distortion across both axes—especially important for long technical documents or detailed engineering schematics.
Summary
In precision-critical environments—such as engineering, manufacturing, surveying, or restoration of historical plans—scanning accuracy is not a luxury; it’s a necessity. To reproduce documents with very small tolerances correctly, you must:
- Account for material deformation over decades of aging.
- Avoid linear array scanners that introduce distortions, particularly over long or uneven originals.
- Use slower scanning speeds to ensure maximum mechanical stability and consistency.
- Rely on CCD scanning technology to maintain true-to-scale reproduction with accurate geometry and depth tolerance.
These considerations are especially vital when digital scans will be used for fabrication, CAD conversion, or legal documentation, where accuracy down to the fraction of a millimetres can have significant consequences.
Conclusion
Although linear array (CIS) scanners offer a convenient and affordable option for general document scanning, they are not suitable for situations requiring high dimensional accuracy and depth tolerance. For engineering, architectural, and construction professionals who rely on scanned images to reflect exact physical measurements, CCD scanners remain the superior choice.
Their ability to preserve scale, compensate for depth variations, and capture minute details ensures that scanned technical drawings retain the integrity needed for analysis, reproduction, and digital archiving. For any project where “drawn to scale” means “measured precisely,” the investment in CCD technology is not just justified—it is essential.
Let ASM DataCore Preserve Your History—Plus Your Accuracy
Whether you’re looking to build a digital archive, convert documents for CAD use, or protect fragile originals, ASM DataCore’s new large-format CCD scanning service delivers unmatched precision and reliability.
Contact us today to book a sample scan or consultation.
