In this paper, we present an open-source tool for calculating the extrinsic calibration between an optical camera and an imaging sonar. Precise determination of the relative 3D location of two sensors is a prerequisite to combining their data into a unified representation of the scene. Optical cameras are commonly used in many robotic domains due to their rich data, low price point, and small form factor. However, optical imagery and the resulting reconstruction degrade quickly in the presence of turbidity and marine snow. Conversely, imaging sonars resolve feature locations in range and azimuth, are largely unaffected by turbidity, but have an inherent elevation ambiguity due to their wide vertical beam pattern. The complementary strengths and weaknesses of these sensors make it appealing to combine them when developing a perception system for use in underwater reconstruction and manipulation tasks. As a first step, an extrinsic calibration describing the relative position of the two sensors must be determined before any data integration is possible. This paper presents a technique that uses a readily-available calibration target and simple hardware to construct a target with both optical and acoustic features and then introduces an open source toolbox for computing the extrinsic calibration.

We present a topographic digital elevation model (DEM) for Princess Elizabeth Land (PEL), East Antarctica. The DEM covers an area of ~900 000 km² and was built from radio-echo sounding data collected during four campaigns since 2015. Previously, to generate the Bedmap2 topographic product, PEL's bed was characterized from low-resolution satellite gravity data across an otherwise large (>200 km wide) data-free zone. We use the mass conservation (MC) method to produce an ice thickness grid across faster flowing (>30 m yr^-1) regions of the ice sheet and streamline diffusion in slower flowing areas. The resulting ice thickness model is integrated with an ice surface model to build the bed DEM. Together with BedMachine Antarctica and Bedmap2, this new bed DEM completes the first-order measurement of subglacial continental Antarctica — an international mission that began around 70 years ago.

In the 2016–2017 austral summer, the University of Texas Institute for Geophysics (UTIG) and the Korea Polar Research Institute (KOPRI) collaborated to perform a helicopter-based radar and laser altimeter survey of lower David Glacier with the goals of characterizing the subglacial water distribution that supports a system of active subglacial lakes and informing the site selection for a potential subglacial access drilling project. This survey overlaps with and expands upon an earlier survey of the Drygalski Ice Tongue and the David Glacier grounding zone from 2011 and 2012 to create a 5 km resolution survey extending 200 km upstream from the grounding zone. The surveyed region covers two active subglacial lakes and includes reflights of ICESat ground tracks that extend the surface elevation record in the region. This is one of the most extensive aerogeophysical surveys of an active lake system and provides higher-resolution boundary conditions and basal characterizations that will enable process studies of these features. This paper introduces a new helicopter-mounted ice-penetrating radar and laser altimetry system, notes a discrepancy between the original surface-elevation-derived lake outlines and locations of possible water collection based on basal geometry and hydraulic potential, and presents radar-based observations of basal conditions that are inconsistent with large collections of ponded water despite laser altimetry showing that the hypothesized active lakes are at a highstand.