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Print Your Compass: Using 3D

Printed Geological Compasses for

Teaching and Research Purposes

Antoine Triantafyllou, Lyon Geology Laboratory—Earth, Planets and Environment (LGL-TPE), Université Lyon 1, ENS de Lyon, CNRS,
UMR 5276, Villeurbanne, France; antoine.triantafyllou@univ-lyon1.fr

MOTIVATION creation networks in academic institutions precision of 2°), and Part 4 is graduated
A geological compass is an essential tool and/or universities (Hasiuk, 2014; de Lamotte from 0 to 360° for azimuth measurement
in the geologist’s field kit. It is used in vari- et al., 2020; Reynolds et al., 2020). respective to north (with a precision of 1°).
ous geosciences disciplines, including geo- This paper aims to provide detailed 3D Graduations can be directly printed onto
logical mapping and structural geology. plans of compass pieces, guidelines for plexiglass pieces or as transparent flipped
The past decade has seen the emergence printing materials, magnets and pivot sys- vinyl stickers placed on their inner side.
of digital geological compasses through tem, and validating the accuracy of printed Small nylon screws are used to fix these
excellent smartphone or tablet apps (e.g., compasses. I hope that such initiatives will windows to the main part of the PYC com-
FieldMove Clino, eGeoCompass, Stereonet allow students from their first degree to pass. Part 5 comprises two levels and the
Mobile), the reliability of which has been master’s level, teachers, and geoscientists in casing of the PYC compass. One rounded
demonstrated for teaching and research general, to print their geological compass at level (15 mm in diameter and 8 mm in
purposes (e.g., Novakova and Pavlis, 2019; a lowered cost, adapted to their specific height) can be embedded on the front side of
Lundmark et al., 2020). Although these dig- needs, and with sustainable manufacturing. the PYC compass to enable levelling, along
ital compasses are highly ergonomic and with a second cylindrical level on the side of
have greatly improved the speed and the HOW TO PRINT YOUR COMPASS the PYC compass to improve finding the
rate of data collection (Zobl et al., 2007; The PYC compass (v.0.94) presented in line of slope on a planar structure. The pro-
Allmendinger et al., 2017), it is essential Figure 1A is designed in five modules. Part tection case, printed here in a flexible resin
that undergraduate students learn how ana- 1 is the core of the compass, printed here (thermoplastic polyurethane), is designed to
log geological compasses work and how to using Selective Laser Sintering (SLS) in laterally slide the PYC compass in it and act
use them to characterize the orientation of rigid Nylon Polyamide (PA12) with a print- as a shock absorber. The whole compass is
given geological structures (i.e., foliations, ing resolution <80 µm. The front side of 10 × 10 × 2.3 cm in size and weighs less
lineations, or a combination of both) and Part 1 is made of a cylindrical cavity embed- than 0.25 kg. It can be easily disassembled,
transcribing this information in the right ding the precision compass, and the back and each of the constitutive pieces can be
format in a notebook. What is the minimum side is marked by a circular gully in which a replaced. The 3D models can be found in
requirement for a geological compass? It 2-mm-wide brass ball will be used as a cli- the supplemental material or here: https://
1
must be equipped with a clinometer, a pre- nometer. Part 2 comprises the magnet and skfb .ly/opCJY. These are licensed under
cision magnetometer—ideally with a fixed pivot system. It is made of a pile of three a Creative Commons Attribution 4.0
circular graduation—a measuring refer- stacked pieces printed using SLS–PA12 International License (CC BY 4.0).
ence trench, and a bubble level. Various (Fig. 1A) in which a brass pivot and four
geological compasses are available on the Nd-magnets (15 mm long × 3 mm in diam- VALIDATING THE PYC COMPASS
market (e.g., Brunton, Freiberg, Topochaix eter) are enclosed. The magnet and pivot ACCURACY IN THE FIELD
brands) with several models in different system is ultimately stacked and sealed by I tested the PYC compass in the field
price ranges. Nevertheless, equipping large two vertical nylon screws. The magnet and and compared measurements against reli-
student groups with robust, accurate, semi- pivot system is balanced on a brass nail able compasses, including the Topochaix
to fully professional models of geological crossing Part 1 vertically. Part 3 and Part 4 Universelle compass and the FieldMove
compasses still represents a significant are the closing windows placed on each side Clino app running on a Samsung S7 smart-
cost. This is why I initiated the PYC (Print of the PYC compass. They both consist of a phone. The test was conducted on the
Your Compass) project, building upon the 2-mm-thick and 80-mm-side square plexi- Moulin de Cezinieux orthogneissic unit
emergence of affordable digital fabrication glass window. They are crucial parts of the located in the northern Pilat region (eastern
tools such as 3D printing, which is particu- compass as they display the graduations for French Massif Central; Fig. 1B). This out-
larly facilitated by the development of precise measurements. Part 3 comes with crop is made of low-dipping metamorphic
shared workspaces such as FabLabs and inclination degrees from 0 to 90° (with a foliations from the late Hercynian orogenic

GSA Today, v. 32, https://doi.org/10.1130/GSATG523GW.1. CC-BY-NC.

1 Supplemental Material. 3D models (as .obj filetype) for each part of the PYC compass. For more details about these files, please contact the author: antoine.triantafyllou@
univ-lyon1.fr. Go to https://doi.org/10.1130/GSAT.S.16900333 to access the supplemental material; contact editing@geosociety.org with any questions.

52 GSA TODAY | January 2022