Orienting paleomagnetic drill cores using a portable GPS compass

Abstract

A portable Global Positioning System (GPS) compass was devised for orienting paleomagnetic drill cores and field test measurements were conducted. Orientation of drill cores has been done by magnetic compasses, sun compasses, and backsighting using landmarks. We modified a lightweight marine GPS compass to be mounted on an orientation device and directly measure azimuths, and compared them to measurements made with a magnetic compass, sun compass, and backsighting. Tests on our campus for a site with open sky above showed a root-mean-squared (rms) error of $$0.39^\circ$$ 0 . 39 ∘ , which is less than what is noted on the specifications of the GPS compass, and a difference of $$-\,0.1^\circ \pm 1.1^\circ$$ - 0 . 1 ∘ ± 1 . 1 ∘ (average ± rms) between the GPS and sun azimuths for 11 direction measurements. However, the site between buildings showed an average deviation of $$11.4^\circ$$ 11 . 4 ∘ from the sun azimuth due to multipath effects. When tested on drill core sampling of historical lavas in a volcanic island, the GPS azimuths were deviated only by $$0.4^\circ \pm 2.3^\circ$$ 0 . 4 ∘ ± 2 . 3 ∘ from the sun azimuths at a flat coastal site with open sky above, indicating that the GPS azimuths are as accurate as the sun azimuths. On the other hand, the GPS compass could not provide azimuths at vertical outcrops in forests due to the small number of satellites captured and multipath effects. If other Global Navigation Satellite Systems (GNSS) satellites are captured and false signals caused by multipath are eliminated, portable GNSS compasses, which operate regardless of rock type, weather, or geographic situation, would replace other methods of orienting drill cores. Graphical Abstract

Orientation Errors of Paleomagnetic Samples When Using a Magnetic Compass and Possible Ways to Overcome Them

“…Для преодоления этих проблем были разработаны другие методики, в частности техника обратного визирования (back-sighting), визирование образца на отдаленный объект и техника с использованием высокоточного GPS позиционирования [2,5,12]. Рассмотрим кратко каждую из этих методик.…”

“…Другой вариант подобной методики представлен в работе [2]. В этом случае используется стандартный корабельный GPS компас, смонтированный на устройство, ориентирующее образцы.…”

“…Масштабы этих искажений оцениваются различными исследователями от незначительных до совершенно неприемлемых (например, [1]). При этом в мировой литературе приводятся только единичные оценки, основанные на реальных экспериментальных результатах [1,2]. Соответствующие публикации в отечественной литературе нам не известны.…”

Interfacing Arduino Boards with Optical Sensor Arrays: Overview and Realization of an Accurate Solar Compass

“…The compasses based on GPS satellite constellations are cheaper than gyroscopic compasses, but their accuracy is worse than our electronic solar compass. Recent works testing the validity of GPS measurements provide accuracies ranging from 0.07 to 1.5 degrees [ 31 ] and from 0.09 to 0.21 degrees [ 32 ], and, in a paper concerning a measurement campaign for the orientation of paleomagnetic drill cores, the RMS deviation of a GPS compass was shown to be well above 0.1° [ 33 ].…”

Oriented Bedrock Samples Drilled by the Perseverance Rover on Mars

“…First, near‐surface (≲20 cm deep) core samples are commonly acquired using a handheld diamond tipped rotary drill (for hard rock) or with non‐rotary drive coring devices (for soft sediments) (Tauxe, 2018; Turner et al., 2015). These are oriented using a sun compass, magnetic compass, and/or a global navigation satellite system and can have uncertainties as low as ±3° (Cañón‐Tapia, 2007; Fukuma & Muramatsu, 2022; Tauxe, 2018). Second, block samples can be chipped off bedrock and typically oriented with a sun compass and/or magnetic compass with uncertainties that can approach those typically achieved with hand held drills (Collinson, 1983).…”