Retrieval of Ice Samples Using the Ice Drone

Abstract

The ecological impacts of meltwater produced by icebergs and sea ice in the waters around Greenland are poorly understood, due in part to limited observations. Current field sampling methods are resource and labor-intensive, and not without significant risk. We developed a small, unoccupied, and robotic platform to retrieve ice samples, while simultaneously eliminating safety risks to scientists and their support infrastructure. The IceDrone consists of a modified commercial hexcopter that retrieves ice samples. We describe the design requirements, construction, and testing of the IceDrone. IceDrone's capabilities were validated in the laboratory and during a field test in January 2019 near Nuuk (southwest Greenland). IceDrone retrieved samples in hard and dry glacial ice in harsh winter conditions. The field test led to modifications in the drilling head design and drilling process that enable it to retrieve samples in thin sea ice. All design files and software are provided in an attempt to rapidly enhance our collective understanding of ice-ocean interactions while improving the safety and productivity of field sampling campaigns.

In situ measurements of the ice flow motion at Eqip Sermia Glacier using a remotely controlled unmanned aerial vehicle (UAV)

“…As a result a horizontal error between 23 and 45 cm was found with a standard mean deviation of 8 cm. This represents an absolute error of about 1-2 pixels, which is slightly less accurate than the error estimate (about 1 pixel) reported by Chudley et al (2019). Further details on SfM-MVS processing can be found in the Supplement of .…”

“…4), we performed photogrammetrical UAV flights to produce ortho-images and digital elevation models (DEMs) of Eqip Sermia Glacier, identify an appropriate landing area, and make an initial estimate of the ice flow. For that purpose, we closely followed the approach described by Chudley et al (2019) and . We briefly describe the method in this section and refer to and its Supplement for more details.…”

“…For inaccessibility reasons, we did not install any ground control points (GCPs) on the sides of the glacier. To ensure an accurate georeferencing of the photogrammetrical results, we used the direct method described by Chudley et al (2019); i.e., the camera location of each picture was determined using an onboard differential carrier-phase GNSS receiver (the same as described in Sect. 4.2), which can deliver relative centimeter accuracy when combined with a second one (called the base station) fixed on the ground.…”

“…For data processing in differential mode this receiver ("rover") works in combination with a second one ("base"), which is fixed on the ground. Differential carrier-phase positioning yields centimeter accuracy (relative to the base station) as long as the distance between the two (base and rover) remains under 10 km, the differential ionospheric delay being negligible for such a small distance (Chudley et al, 2019). Although the Emlid receiver can be used for real-time kinematics (RTK) (i.e., providing the centimeter-accurate position of the UAV in real time), we used it only in postprocessed kinematic (PPK) mode for simplicity; i.e., we downloaded the log files of the rover and the base station once the measurements were completed and processed them afterwards via the open-source software RTKLIB (http: //www.rtklib.com/rtklib.htm, last access: 6 February 2020).…”

“…Alternatively, one can use laser scanning (Pętlicki and Kinnard, 2016) or interferometric radar (Riesen et al, 2011;Lüthi et al, 2016) to increase the temporal resolution of data; however, the spatial coverage of such ground-based instruments remains limited. In recent years, unmanned aerial vehicle (UAV) photogrammetry by structure-from-motion multi-view stereo (SfM-MVS) has been increasingly used for the remote sensing of glacial motion at high spatial resolution (Immerzeel et al, 2014;Ryan et al, 2015;Jouvet et al, 2017;Kraaijenbrink et al, 2016;Benoit et al, 2019;Chudley et al, 2019).…”