Rogerio.monteiro@vektore.com

Open-Source Core Alignment Tool: Better Core Orientation, Better Models

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What if a simple, free tool had the potential to enhance the accuracy of your core orientation data?

​Structural geology data derived from oriented core is crucial for understanding the orientation and configuration of geological structures, not only while evaluating the magnitude and continuity of mineralization but also providing evidence for such continuity when migrating between the mineral resources’ classes. The accuracy of these measurements can be broadly divided into two categories: (Vektore 2025):

  1. Measurement-Instrument Accuracy: this pertains to errors related to the direct reading from the core, often influenced by the actual reading method or tool used.
  2. Measurement-Net Accuracy: cumulative error that builds up over the course of each core orientation run.

A significant source of error arises from the orientation process itself or the transfer of the orientation mark to the core – this issue is prevalent in the industry and often goes unaddressed at the drilling site. However, it is important to acknowledge that mitigation strategies exist to address these issues at the core shed; practices proposed by @Holcombe (2014) offer approaches to quantify and qualify such errors. Consider a stereonet generated from multiple core orientation runs, each recording a consistent foliation orientation. Ideally, the data points should be clustered. However, due to misorientation, these points often scatter along a small circle (cone), reflecting discrepancies that can compromise geological interpretations and resource estimation. Addressing Core Orientation Misorientation is crucial for enhancing the reliability of structural data in mineral exploration.

To ensure data integrity, it’s often recommended to discard unreliable core-orientation runs—sometimes accounting for over 70% of all runs. We’ll illustrate this with a case study and explore it further in an upcoming article. As noted by @Brett Davis (2012), geologists must vigilantly assess the quality of orientation marks and be prepared to discard data that does not meet established standards. Any deviation in this process can proportionally impact the outcome of the intended work. Therefore, achieving high accuracy at the reading stage does not guarantee the overall accuracy of the data and its usability. Indeed, when orientation errors accumulate, geological models become inaccurate, leading to misplaced drillholes, flawed resource estimates, and ultimately costly mining decisions.

 Another typical challenge regarding the core orientation mark arises when the core break occurs inside the core lifter case (core piece locked to the core lifter). In this case, the mark is usually not transferred by the drillers due to the lack of a proper tool to place the core orientation mark at the face of the core. Moreover, a rapid test to verify the consistency of orientation marks across successive core runs – without the need to fully trace the orientation line – would be a valuable tool as an effective first-pass quality control measure in the geologist’s toolbox.

 Before outlining our solution to the core orientation issues described above, we must first introduce five key concepts: Locked Intervals, Tau Angle, Core Orientation Misorientation, Core Orientation Drift, and Indented Orientation Mark.

  • Locked Intervals refer to physically continuous sections of core where all pieces remain in contact and properly assembled as they were in situ. These intervals may be shorter or span one or more drilling runs and serve as the fundamental units for evaluating orientation consistency.
  • Tau Angle is the angular difference between two orientation lines derived from two adjacent and connected core runs as calculated by Vektore’s Structural Vectoring Log method (Vektore 2012-2025a) – a value that, in a perfectly oriented core, should be zero. It quantifies between-runs misalignment and is conceptually described by Holcombe (2013) as the Spin Angle, followed by Meyers et al. (2016) as the Lock Angle.
  • Core Orientation Misorientation errors are introduced when transferring orientation marks from the core orientation tool to the core, resulting in non-zero Tau Angles between two contiguous and locked core runs (e.g., see Interval 12 on Figure 3). Such misalignments are prevalent in the industry and often lead to substantial deviations in structural data.
  • Core Orientation Drift is a systematic, cumulative misorientation between successive core runs – evidenced by growing Tau Angles and directional bias – often a downstream effect of misorientation (e.g., see Interval 12 on Figure 3).
  • Indented Orientation Mark is the orientation line placed on the face of the last core piece, from the core orientation run, while it is still secured within the core lifter, at the inner end of the core lifter case.

 vCAT© – Vektore Core Orientation Tool

To address the challenges outlined above, Vektore designed and developed the vCAT (Vektore Core Alignment Tool – Figure 1) in 2020. Since its launch (Vektore, 2020), vCAT has become an integral part of our services, enabling clients to enhance core orientation accuracy in mineral exploration projects. Vektore gratefully acknowledges the contributions of @Rodrigo Figueiredo, @Rogerio Monteiro, @Tiago Eloi, and @Angelo Giovannone to the design and implementation of vCAT. To support the broader industry, we are releasing vCAT as a free, open-source tool under the Creative Commons license: vCAT – Vektore Core Alignment Tool © 2020 by Vektore Exploration Consulting Corporation is licensed under CC BY-NC-SA 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/4.0/. This initiative aims to make vCAT widely accessible, enabling professionals, educators, and field teams worldwide to adopt better core alignment practices and improve the reliability of structural data acquisition.

 vCAT (Figure 1 and Figure 2) is a purpose-built device designed to enhance the accuracy of core orientation mark transfers and thereby enhance the quality of the core orientation line. It offers a precise and user-friendly solution by physically snapping into the core lifter case, utilizing strong magnets to ensure stable and accurate alignment transfer – whether the core is indented or protruding. This enables reliable transfer of the Top-of-Core (TOC) or Bottom-of-Core (BOC) orientation mark onto both the core’s side and face, while mitigating common issues such as orientation drift (Figure 3).

vCAT supports three key use cases:

  1. Reliable orientation transfer: transferring core orientation marks–Top-of-Core (TOC) or Bottom-of-Core (BOC) – onto the core with consistency.
  2. Indented face marking: accurately marking the core face when the final piece is recessed or indented in the core lifter case.
  3. Rapid alignment checks: conducting quick alignment checks between locked core runs without the need for tracing the full orientation line, either at the drill site or later in the core shed.

vCAT enables accurate alignment in the field or core shed, allowing exploration teams to detect and correct orientation errors early before they incur costly consequences. It significantly improves the accuracy of structural measurements by enhancing measurement-net accuracy.

vCAT (Vektore Core Alignment Tool) – Key Features:

  • Precise core alignment: physically snaps into the core lifter case (V-house and magnets), promoting stable and accurate alignment during orientation mark transfers.
  • Handles irregular core surfaces: effectively enables orientation marking on cores that are recessed or protruding within the core lifter case, including top, bottom, and face orientations.
  • Increases the number of usable core orientation runs: provides a reliable method for transferring orientation marks, allowing more core runs – including those with breaks inside the core lifter case – to meet quality standards and be included in structural analyses.
  • Mitigates orientation drift: addresses common issues related to core orientation drift, enhancing the reliability of structural data.
  • Quick verification between runs: enables rapid alignment marks checks between adjacent core orientation runs, eliminating the need to draw the full orientation line – core must be sitting on an angle iron and core pieces locked as they were in situ.
  • User-friendly design: features an easy-to-use snap-fit mechanism compatible with any inner tube and core lifter case, suitable for all field conditions. Intuitive operation and quick setup optimized for practical field conditions.
  • Non-electronic and durable: operates without electronic components, reducing potential points of failure in rugged environments.
  • Accessible and customizable: designed for 3D printing with simple parameters, making it easy to produce and adapt as needed – open call for collaboration and feedback.
Figure 1 Shows the vCAT© tool – the numbered labels represent key components: (1) bubble, (2) magnet to lock onto the core lifter case, (3) pivoting support to transfer the core orientation mark to core face when it is locked inside the core lifter (indented core), and (4) magnet to lock the pivoting support. The three blue arrows indicate the location of the three aligned V-house slots to be used to constrain the marker along the proper alignment in relation to the core orientation information.

 

Figure 2 This image shows one of the various setup configurations for using the vCAT© tool. It is locked on the core lifter case and showing the Top of the Core line transferred to the core. Note that the pivot V-house slot properly constrains the marker orientation. This pivot V-house slot is also used to project the orientation mark into the core face when it is residing and locked inside the core-lifter. Note that the semi-ellipse, the line and the letter “T” are Vektore’s best practices to make the Top-of-Core mark self-evident.

 

The Tau Plot (Figure 3) illustrates core misorientation by visually classifying the reliability of core orientation data. It also serves as a diagnostic tool to address these issues through the application of the Structural Convergence© method (https://vektore.com/orenode/), which is part of Vektore’s Quality Optimization process.

Figure 3 Ore.node’s Tau plot showing the core orientation misorientation patterns emerged from 105 m of locked core, providing a full evaluation of the health of the continuously locked intervals. Core orientation drift is shown on the interval 12 (under the curly bracket). Note that up to 20% of the runs are aligned and indicated by the second curly bracket – and in between these two brackets, there is a 1800 rotation (red rectangle). In addition, there is a missing connection at the end of the Tau Plot. These are errors easily spotted by the Tau Plot with locked runs of any length. One of the causes of core orientation misorientation is related to the design of the tools used to transfer the core orientation information onto the core, which can be significantly influenced by the diameter of the marker and by how the driller transfers such information to the core. Note that the Tau Plot allows real-time analysis and Quality Optimization© (based on the Structural Convergence method Vektore (2012–2025b)) without the need for redrawing the core orientation lines.

 

Conclusion

Accurate core orientation is fundamental to reliable structural geology and mineral resource estimation. Nevertheless, errors during the transfer of orientation marks to the core remain a common and often overlooked issue in the industry. These misalignments can cascade through the data pipeline, leading to costly mistakes in structural interpretation, geological modeling and decision-making.

To effectively address this challenge, Vektore has developed the vCAT (Vektore Core Alignment Tool) – a simple, non-electronic tool designed to improve the accuracy of orientation transfer. By releasing vCAT as a free, open-source tool under the Creative Commons license (CC BY-NC-SA 4.0), Vektore aims to make this solution tool widely accessible, enabling professionals, educators, and field teams worldwide to adopt more reliable core alignment practices and enhance the quality and trustworthiness of structural data acquisition.

Key Takeaways:

  • Core orientation errors are widespread in the industry: misorientation during the transfer of orientation marks is a significant source of error in structural geology.
  • vCAT offers a practical solution: designed by structural geologists, vCAT addresses common alignment issues, aiming to enhance the accuracy of structural data.
  • Open-source accessibility: by releasing vCAT under a Creative Commons license, Vektore empowers the global geological community to adopt better core alignment practices.
  • Enhanced data reliability: vCAT contributes to more accurate geological interpretations and resource estimations, ultimately supporting more efficient and cost-effective exploration outcomes.

In summary, vCAT is designed to support the Value of Information in mineral exploration by offering a cost-effective approach to core orientation that has the potential to help informed decisions and enhance exploration efficiency. Explore the vCAT – download it to improve consistency and alignment practices in your core orientation program [vCAT 3D drawings].

Disclaimer

The vCAT (Vektore Core Alignment Tool) is provided by Vektore Exploration Consulting Corporation (Vektore) under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License (CC BY-NC-SA 4.0). This license allows users to use, share, and adapt the tool for non-commercial purposes, provided proper attribution is given to Vektore and any derivative works are distributed under the same license.​ The tool is provided “as is” without any warranties, express or implied, including but not limited to warranties of merchantability or fitness for a particular purpose. Users are responsible for ensuring the tool’s suitability for their specific applications and for complying with all applicable laws and regulations. Vektore shall not be liable for any damages, losses, or other liabilities arising from the use or inability to use vCAT, including but not limited to direct, indirect, incidental, or consequential damages.​ By downloading, printing, or using vCAT, you acknowledge and agree to the terms of the CC BY-NC-SA 4.0 license (https://creativecommons.org/licenses/by/4.0/legalcode) and this disclaimer. Commercial Use Notice: the design files are provided free of charge for personal and non-commercial use only. If you are interested in manufacturing and/or commercializing any product based on these design files, please contact Vektore to obtain a separate commercial agreement.

List of materials – see on webpage

Here is the list of materials necessary to build vCAT:

  • 3D printer
  • 3D print filament or resin
  • Eight Rare Earth strong magnets – 12 mm x 3 mm
  • Two Rare Earth strong magnets – 4mm x 2mm
  • Cylindrical Bubble Level 9.5x40mm

References

Davis, B. (2012). Drill core orientation – An Inconvenient Truth, part 2 of 3 – https://structuralgeology.com/drill-core-orientation-an-inconvenient-truth-part-2-of-3/?utm_source=chatgpt.com.

Holcombe, R. J. (2014). Oriented Drillcore: Measurement, Conversion, and QA/QC Procedures for Structural and Exploiration Geologists – last updated in May 2023. https://www.holcombe.net.au/downloads/HCOVG_oriented_core_procedures.pdf.

Myers, R. et al. (2016) An Inexpensive Way to Maximize and Preserve the Value of Oriented Core: The Orientation Log. SEG Discovery (107): 1–19.

Vektore (2020) Various designs & built of the vCAT – internal documents.

Vektore (2025) How Accurate are Alpha and Beta Measurements? Responding to Federico Arboleda and tackling the elephant in the room. (https://www.linkedin.com/pulse/how-accurate-alpha-beta-measurements-responding-federico-arboleda-iahtc/?trackingId=lPdlhKKkP%2Bv2JGQSNhbheg%3D%3D or https://vektore.com/how-accurate-are-alpha-and-beta-measurements-responding-to-federico-arboleda-and-tackling-the-elephant-in-the-room/).

Vektore (2012-2025a) Vektore Webpage at www.vektore.com

Vektore (2012–2025b) various webpage posts, short courses and presentations: Structural Geology in Mineral Exploration (short courses to the University of Western Ontario and industry clients); Structural Vectoring Log (SVL) methodology guide; Best Practices in Structural Exploration Geology and Standard Operating Procedures; Ore.node, vSTAR, and vSTAR App.

 

(2) magnet to lock onto the core lifter case, (3) pivoting support to transfer the core orientation mark to core face when it is locked inside the core lifter

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