Ten-year-old girl killed in mudslide in North Yorkshire, UK.

A ten-year-old girl has been killed by a mudslide while on a forest walk at Carlton-in-Cleveland on the edge of the North York Moors National Park in North Yorkshire, England, on Wednesday 22 May 2024. Leah Harrison from Darlington, was on a week-long residential school trip to the Carlton Adventure activity centre to celebrate the completion of SAT Tests (Standardised Assessment Tests, or SATs, are national assessments that are administered by primary schools in the UK), when the incident happened. An investigation into the event is being carried out by North Yorkshire Police and the Health and Safety Executive.

Leah Harrison (10), killed by a mudslide at Carlton-in-Cleveland in North Yorkshire on 22 May 2024. North Yorkshire Police.

The incident happened following a period of heavy rainfall in the area, with as much rain falling in the 12 hours prior to the incident as typically fall in a month in the area. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. A Yellow Weather Alert had been issued at the time of the accident, the lowest level of such alerts in the UK, which would lead people to expect some disruption to travel or outdoor events, but not significant danger.

The UK has been suffering a series of extreme weather events, including flooding and tornadoes, driven by exceptionally high temperatures over the Atlantic Ocean. As the air is heated the air pressure drops and the air rises, causing new air to rush in from outside the forming storm zone. If this zone is sufficiently large, then it will be influenced by the Coriolis Effect, which loosely speaking means the winds closer to the equator will be faster than those further away, causing the storm to rotate, clockwise in the northern hemisphere and anticlockwise in the southern hemisphere.

The high temperatures experienced in the past year have been linked to a combination of anthropogenic global warming, driven by emissions of carbon dioxide and methane, with an El Niño - Southern Oscillation climate system over the Pacific Ocean, a natural phenomenon which also tends to drive temperatures upwards. However, the El Niño system appears to have been weakening over the past months, with sea surface temperatures over the eastern equatorial Pacific actually being lower than the average for 1990-2020, while global temperatures have continued to rise, suggesting that the El Niño system may be playing as large a role in driving this year's high temperatures as previously assumed.

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Elaborate Roman mosaic uncovered at Mérida in the Extremadura Region of western Spain.

Students from the Escuela Profesional Barraeca II del Ayuntamiento have uncovered a large and elaborate Roman mural while carrying out excavation work at the Huerta de Otero archaeological site in the city of Mérida in the Extremadura Region of western Spain, according to a press release issued by the Mérida Ayuntamento on 26 July 2023.

Partial view of a Roman mosaic uncovered by students from the Escuela Profesional Barraeca II del Ayuntamiento at Mérida in the Extremadura Region of western Spain. Mérida Ayuntamento.

The multi-coloured mosaic covers an area of about 30 m², and has a central motif depicting the head of Medusa within an octagonal medallion, surrounded by four Peacocks, within a wider square with a variety of images of Fish, Birds, Jellyfish, masks, and geometric shapes. The mosaic is thought to have been associated with a sixth century AD bathhouse.

The central Medusa motif of the Huerta de Otero mosaic. Mérida Ayuntamento.

The Huerto de Otero site was discovered in 1976, when some preliminary exploration work was carried out, but full scale excavations did not begin until 2019, when a joint project by the Mérida Ayuntamento and the Consorcio y el Instituto de Arqueología de Mérida was set up to manage the site. Fifteen students from the Escuela Profesional Barraeca II del Ayuntamiento began working on the project in September 2022, as part of a work-placements scheme which is credited with gaining 85% of the school's students a job in their chosen field.

One of the Peacocks surrounding the central Medusa motif of the Huerta de Otero mosaic. Mérida Ayuntamento.

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Eighteen students injured as primary school classroom collapses into sinkhole in Zimbabwe.

Eighteen children have been injured after a classroom collapsed into a sinkhole at a primary school in Zimbabwe on Thursday 16 March 2023. The incident happened at about 7.30 am local time, the Globe and Phoenix Primary School in the town of Kwekwe in Midlands Province, about 200 km from Harare, and affected a classroom where grade five students were being taught, which in Zimbabwe implies 10-11 year olds. The school, which has about 1500 pupils, has closed following the incident, with 900 of the pupils having been offered temporary places at the nearby Sally Mugabe Primary School, while the rest will attend classes in large tents erected in the grounds of the Globe and Pheonix School.

Members of the emergency services inspect a classroom which collapsed into a sinkhole in Kwekwe, Zimbabwe, on 16 March 2023. Zimbabwe Situation.

Sinkholes are generally caused by water eroding soft limestone or unconsolidated deposits from beneath, causing a hole that works its way upwards and eventually opening spectacularly at the surface. Where there are unconsolidated deposits at the surface they can infill from the sides, apparently swallowing objects at the surface, including people, without trace. 

However, on this occasion the hole is believed to have been caused by the a collapse within an old gold mine, which underlies the school and which has recently become a centre of activity for illegal miners. The Globe and Phoenix School takes its name from the Globe and Phoenix Mine, a gold mine which operated from the 1890s until 2007, when it  was closed down in 2007 by the Ministry of Mines and the Environmental Management Authority, following a series of safety problems, having originally been founded to educate the children of miners working at the mine.

While there is currently no official mining activity at the site (there are plans for such activity to restart in the future), the mine has become a target for informal miners, who work within many disused mines within Zimbabwe, a practice which is illegal but generally tolerated by the authorities, a country plagued by high unemployment and other economic problems, and is recognized as making a significant contribution to the economy, as such miners are able to sell their product locally rather than smuggling it out to avoid the attention of local authorities, as happens in many African countries. However, the informal nature of this industry makes it extremely dangerous, as few if any health and safety precautions are taken in such mines, and their are occasional reports of armed clashes between rival groups over lucrative sites.

This is particularly problematic at the Globe and Phoenix Mine, which was excavated using a gallery and pillar system, in which pillars of material were left as supports as a seem of gold ore was removed. These remaining pillars have a higher gold content than the unexcavated parts of the seem (which were deemed not economically useful by the original mining company), and are an obvious target for artisanal miners, weakening the structure of the mine, and leading to collapses. 

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Tackling racial diversity in the geosciences.

The evolution of the modern geosciences was closely linked to the expansion of European colonial powers, at a time when it was widely believed, at least by the European ruling classes, that the land belonged to those who were willing to use its products. At this time little thought was given to the opinions or welfare of indigenous non-European peoples. This meant that, to a large extent, the geosciences developed as a means to understand the distribution of mineral resources, with a view to extracting them for the benefit of the colonial powers. This knowledge is still important; without an understanding of the distribution of mineral resources, equitable sustainable development would be close to impossible. However, in order for this knowledge to be used for the benefit of the whole community, then the geoscientists wielding it need to reflect that community, and include people from a wide range of people from different communities and walks of life.

Achieving diversity within the geosciences requires robust measures to promote inclusivity, particularly within the former colonial powers. The geoscience disciplines in the Global North are still very much a white discipline, which appears to be a result of both subject-specific issues, and the wider problems of systemic racism within academia. For example, in the US just 6% of doctorate degrees in geoscience disciplines are awarded to students from under-represented minority backgrounds (defined in the US as American Indian or Alaska Native, Black or African American, Hispanic or Latino), despite the fact that these groups make up 31% of the total population. In order to become more inclusive, the biases and hostile environments that have led to this imbalance need to be addressed, and institutions need to work harder to both recruit people from a wider range of backgrounds, and to retain such recruits throughout their careers.

The US actively records data on the backgrounds of students achieving post-graduate qualifications in the geosciences (and other disciplines), but such information is less widely collated in other nations of the Global North.

In a paper published in the journal Nature Geoscience on 29 April 2021, Natasha Dowey of the Department of the Natural and Built Environment at Sheffield Hallam University, Jenni Barclay of the School of Environmental Sciences at the University of East Anglia, Ben Fernando of the Department of Earth Sciences at the University of Oxford, Sam Giles of the School of Geography, Earth and Environmental Sciences at the University of Birmingham, Jacqueline Houghton of the School of Earth and Environment at the University of Leeds, Christopher Jackson of the Department of Earth and Environmental Sciences at the University of Manchester, Anjana Khatwa of Wessex Museums, Anya Lawrence, also of the School of Geography, Earth and Environmental Sciences at the University of Birmingham, Keely Mills of the British Geological Survey, Alicia Newton of the Geological Society of London, Steven Rogers of the School of Geography, Geology and the Environment at Keele University, and Rebecca Williams of the Department of Geography, Geology and Environment at the University of Hull, seek to address some of the issues surrounding inclusivity in the geosciences in the UK. Dowey et al. use data from the UK Higher Education Statistics Agency, which paints what they describe as a 'dismal picture' of inclusivity in the UK, and further note that similar data would be very hard to collect for most other European countries, as such data simply isn't collected at all.

Four of the authors of the paper come from BAME backgrounds (Black, Asian and minority ethnic, the terminology currently used by the UK Higher Education Statistics Agency, but which Dowey et al. recognise homogenises different identities and can obscures experiences felt by one race or ethnicity). The majority of the authors have never been the victims of direct racism, but several hold responsibilities for equity, diversity and inclusion with different organisations, and all are concerned about the current situation, and wish to challenge geoscience leaders in both industry and academia to listen to a wider range of voices, address existing biases and inequalities in the field, and build a more inclusive and accountable culture within the geosciences as a whole.

The UK education system seldom if ever acknowledges the connection between the growth of our modern understanding of the geosciences (or geography in general) and the colonial expansion of the European powers. Furthermore, geoscientists are generally depicted as white men involved in a rugged, outdoors activity, something generally discouraging to people from minority backgrounds. This is reflected in the promotional materials produced by UK universities and geoscience organisations with a public engagement remit, which tends to be filled with images of white students exploring dramatic landscapes.

A recent survey by the Geological Society of London found that 60% of undergraduate geology students cited a lifelong interest in the natural environment. However, access to such environments is often governed by the environment in which one grows up, with children growing up in urban areas and in particular those from low income households, typically having far less ability to interact with the natural environment. Demographic studies of the UK suggest that over 98% of Black African, Pakistani and Bangladeshi people live in urban locations, and that Pakistani, Bangladeshi, Chinese and Black children are more likely to live in low income households that White children. A study by the UK Department for Environment, Food and Rural Affairs found that 18% of children living in the most deprived areas never visited the countryside, and that those from Black and Asian families did so the least. Furthermore, a career in the geosciences is generally less likely to be seen as financially secure that a career in other professions by members of many minority communities.

Analysis of applications data has found that high-tariff, research-led, institutions were less likely to accept that students from BAME backgrounds than White students with similar qualifications. As an example, Dowey et al. cite the case of Oxford University, where it has been shown that BAME applicants are 5.8% less likely to receive a placement offer on mathematical, physical and life sciences courses than White students with similar qualifications. Overall Black students make up 3.9% of the toral number of students at high-tariff universities (universities that require high pre-university grades to gain entrance), and 12.2% of students at low-tariff universities (universities that require lower pre-university grades to gain entrance). Once enrolled, Black students are significantly less likely to gain either a first or 2.1 degree than White students. This in turn impacts the number of Black students gaining entrance to PhD placements, where there is a marked preference for students who have completed their undergraduate degrees at high-tariff universities, and application processes often reflect the candidate's access to resources as much as their actual ability, which strongly stigmatises students from less well off communities. In 2018/19 only 9% of UK Research and Innovation funded studentships, and only 6% of Environment Research Council studentships, were awarded to ethnic minority candidates, at a time when 19.4% of 18–34 year olds identified as BAME.

 

Representation of BAME students in the geology, environmental science and physical geography, shown alongside data for the overall physical sciences subject area and ethnicity data from the 2011 UK Government Census. UK Higher Education Statistics Agency data, based on full-time ‘all undergraduate’ and full-time ‘postgraduate research’ categories and are a five-year mean of data from 2014/15 to 2018/19. Dowey et al. (2021).

Dowey et al. also note that a lack of positive role-models within the field also probably serves as a discouragement to BAME students. Only 10.8% of UK professors identify as BAME, falling to 3.9% in Earth, marine and environmental sciences; the second lowest of any science, engineering and technology discipline. This creates an ‘institutional whiteness’ that can leave BAME students feeling isolated within institutions, and leaves the few BAME staff burdened with the additional responsibility of advancing equality without any meaningful reward.

Studying geosciences can also present additional, subject-specific, boundaries to BAME students, including cultural problems, such as co-educational residential trips and a prevalent ‘alcohol culture' in many geoscience departments and at conferences, as well as the high costs associated with fieldwork, which can impact students from economically disadvantaged communities, and more obvious problems of racial harassment, which can be a problem for students carrying out fieldwork in some areas.

These boundaries do not exist in isolation, students may also be impacted by other issues relating to gender, sexuality, disability, class, or nationality, and therefore increasing the accessibility of institutions to BAME students should be seen as part of a wider drive to make the geosciences an option for a wider range of minority groups.

In recent years there has been a drive for academic institutions to address their past links to colonialism. Within the geosciences, geologists such as Adam Sedgwick and Henry de la Beche are often cited as founding figures within the discipline, without mention of their links to the slave trade. Mapping and surveying are (inevitably) taught as a part of geosciences courses, but seldom with any mention of how these techniques were developed as part of a wider British colonial expansion, nor with reference to the ongoing destruction of sites deemed important by indigenous cultures by mining or civil engineering projects. Moving forward, Dowey et al. hope that geoscientists will work more closely with social and historical scientists to find ways to find ways to teach these subjects in a positive way with a stronger emphasis on geoethics.

 

Adam Sedgwick (1785-1873), proposed the Cambrian and Devonian periods of the geological timescale, and is considered one of the founders of modern geology. He was a vocal supporter of the abolition of slavery, but is also known to have owned slaves on plantations in Jamaica, and upon the abolition of slavery by the British government, received £3783 1s 8d in compensation for the loss of 174 slaves. Thomas Philips (1770-1845)/The Adam Sedgwick Collection/Wikimedia Commons.

A traditional approach to the geosciences is often one in which a Western field scientist visits a location, removes samples (often with local help), takes them back to a Western institution for study, then publishes their results in an (often paywalled) Western publication, without input from, or acknowledgement of, local authors. Such work seldom takes into account the views of local populations.

The tenth of the seventeen United Nations Sustainable Development Goals is the reduction of inequality within and between countries. Achieving this is generally accepted as being impossible without developing a more sustainable society, something which has major implications for the geosciences. Teaching a more inclusive geoscience curriculum, which takes into account a wider range of cultural perspectives, should enable students of all races and ethnicities to participate in shaping the future of the discipline.

Universities and other institutions have the ability to invest resources in racially diverse promotional materials and ambassador schemes that reward outreach work, rather than simply relying on BAME students to fit in with existing structures. There are existing organisations, such as Black In Geoscience and Black Geographers, which promote the role of BAME people within the geosciences, and by working with these educational institutions can promote more diversity within the field. Inviting a more diverse range of people to deliver seminars and presentations within universities can make BAME workers (and other minorities) more visible within the field, and more work can be done to increase the diversity of faculty members, by implementing development opportunities aimed at such staff, to counterbalance existing pathways which tend to favour a narrower range of workers.

Such work also needs to take place at earlier stages in the education system, in order to better access to the natural environment for younger members of BAME communities. Natural heritage organisations should work more closely with such communities, possibly by working with organisations such as Black2Nature, run by youth campaigner and environmentalist Mya-Rose Craig, which has opened pathways enabling young people from deprived areas in Bristol to learn about birding, conservation and wildlife. Universities can also promote such access through targeted outreach activities.

 

Youth campaigner and environmentalist Mya-Rose Craig (aka Birdgirl). Black2Nature/Facebook.

There are a number of steps that can be taken to make fieldwork more accessible to ethnic minority students. Notably, fully subsidising the cost of field-trips and equipment costs would remove boundaries to fieldwork for students from low-income backgrounds, and carrying out racial risk assessments ahead of planned fieldwork. Staff can also benefit from anti-discrimination and allyship training, and all race-related incidents should be fully documented. Courses should also be carefully planned so that fieldwork requirements do actually relate to the intended learning outcomes; many professional bodies require a mandatory number of days of fieldwork for the accreditation of courses, which promotes the traditional image of White, male, students involved in macho outdoor fieldwork, but often does not greatly enhance learning outcomes.

Students from minority backgrounds can also be helped by creating ring-fenced opportunities which address their needs, such as funded research experiences, summer schools, internships and studentships. More can be done to work with schools, colleges and other universities, to make students aware of such schemes where they exist.

Funding organisations and institutions need to be held accountable for transparency in their recruitment processes, and members of interview panels need to understand the barriers to BAME students, in order to to ensure improved diversity in successful applicants. Demographic data on candidates at the application, interview, offer and acceptance stages, should be published, in order to provide a clearer picture of postgraduate recruitment diversity.

Efforts to improve diversity should not be seen as ending at recruitment; more resources should be allocated to training in equity and inclusion. Diversity 'champions' can support the interests of minority candidates and groups, and encourage institutions to reflect on practices which produce hostile environments.

Dowey et al. argue that universities and other higher institutions need to acknowledge the hostile environments that can exist within them, which can discourage BAME students from both applying to, and continuing within geoscience disciplines. In order to make sure efforts to resolve these problems are long-lived, evidence-driven research needs to be undertaken to make sure the causes of problems are well understood, and efforts should be made to collaborate with other subjects and bodies facing similar challenges, thereby sharing transferable solutions across the sector. Workers in higher education must address personal and structural biases, and strive to be actively anti-racist. Finally, Dowey et al. note that the less diverse a field is, the more prevalent implicit biases become, and that difficult conversations need to happen sooner rather than later in order to create a more diverse and inclusive geoscience research culture.

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Combining photography and computed tomography to make three dimensional models of the Blaschka Glass Marine Invertebrates.

An increasing number of museums are using 3D imaging both for archival recording and to allow the global public to experience objects in collections that they would otherwise never be able to get close to. Photogrammetry, optical scanning and X-ray computed tomography scanning are all being used. These efforts benefit from steadily improving technology and abundant software options, and they build on extensive earlier work done primarily in archaeological, zoological and biomedical applications. Notable efforts are those at the Smithsonian Institution and the British Museum. However, rendering 3D images that are faithful to the original object remains difficult for many specimens. Fine detail or lack of detail, thin structures, hidden or glossy surfaces, and transparent or semi-transparent volumes are a few of the challenges. Intricate antique glasswork, while especially challenging for 3D imaging, also benefits tremendously from it because the specimens are typically very fragile; for conservation reasons, they should be handled as little as possible, if at all.

In a paper published in the journal Digital Applications in Archaeology and Cultural Heritage in September 2020, Peter Fried of the Department of Applied Physics at the New York University Tandon School of Engineering, Jonathan Woodward of the Museum of Comparative Zoology at Harvard University, David Brown of the Herbert F. Johnson Museum of Art at Cornell University, Drew Harvell of the Department of Ecology and Evolutionary Biology at Cornell University, and James Hanken, also of the Museum of Comparative Zoology at Harvard University, present the results of a project which for the last three years has been making 3D images of the intricate and beautiful glass models of Marine Invertebrates created between 1863 and 1890 by the father and son team of Leopold and Rudolf Blaschka.

The Blaschkas made thousands of these models, principally as teaching aids. They were shipped from the Blaschkas’ workshop in Dresden, Germany, to universities, schools and museums around the world. The Blaschkas made their models based on their own extensive observations of living Animals in aquaria and during several ocean voyages, and also based on drawings by contemporary taxonomists. The glass models of soft Marine Invertebrates were especially valuable because the shape and color of live specimens did not preserve well after death in fixatives used at that time. These models serve as a record of ocean life 100 or more years ago, and therefore are valuable to studies of evolution and the impacts of climate change.

Today, the principal collections of Blaschka Marine Invertebrate models are at Cornell University, the Harvard Museum of Comparative Zoology, the Corning Glass Museum, and University College, Dublin. Many smaller collections exist at institutions around the world. Fried et al. have imaged models at Cornell University and the Harvard Museum of Comparative Zoology.

Fried et al.'s imaging work began with glass models that are relatively simple in form and completely painted, so as to develop the basic photogrammetry workflow required, e.g. the minimum numbers of photographs and angles needed to yield high-resolution images. They then optimised control of the lighting, especially polarisation, using somewhat more complicated models that include sections of bare glass and/or glossy paint. Finally, there are some models with substantial transparent areas and/or intricate detail for which photogrammetry alone is inadequate. For these models, Fried et al. generated meshes with both photogrammetry and X-ray computed tomography scanning, which were then combined to create the final reconstruction.

 

European Squid, Loligo berthelotii. Model B-560 of the Cornell University Collection of Blaschka Marine Invertebrates (length about 6.4 cm). Fried et al. (2020).

The photogrammetry involved between 250 and 700 photographs of each glass model, which were taken against a black background on a turntable using 2–4 different camera angles. When possible, the model was arranged on the turntable in several different orientations to achieve 2–3 more or less orthogonal axes of rotation. A large number of photographs is needed both to insure good inter-photo registration, or 'alignment', and to insure adequate coverage of the entire complex geometry of the models. To further insure proper alignment, distinct coloured targets were mounted on the turntable, away from the glass model, near the edge of the field of view.

 

Fontaine’s Octopus, Robsonella fontanianus. Model SC-380 of the Harvard Museum of Comparative Zoology Collection of Blaschka Marine Invertebrates (spanning 13 cm from arm to arm). Fried et al. (2020).

Traditionally, specular reflections are minimized by applying a powder or spray coating to the subject. Such treatment, however, is not possible for the Blaschka models, especially in view of the fragile organic paints used to manufacture many of them. Controlling the polarisation of incident light by applying filters to the lens and/or the lights themselves can also be used to minimize (or maximize) specular reflections.

 

Stout Bobtail Squid, Rossia macrosoma. Model B-588 of the Cornell University Collection of Blaschka Marine Invertebrates (length about 15 cm). Fried et al. (2020).

The final position of the camera and lights was a compromise among the polarisation control and additional issues: The need for high resolution; the need to maximize relative depth of field; the need to minimise exposure time; and available resources, including lenses and controllable polarisers.

 

Sea Anemone, Phymactis pustulata. Model SC-51 of the Harvard Museum of Comparative Zoology Collection of Blaschka Marine Invertebrates (width about 10 cm). Fried et al. (2020).

For the 3D models illustrated here, Fried et al. used a 55 W, 1400- diameter ring light and a Nikon 7100 DSLR camera with an 80- or 90-mm macro lens. Lights and lens were located between one and three feet from the turntable. Apertures of f11–f20 were generally used. The camera, mounted on a firm tripod, was usually operated by remote control and typically set at a high ISO value (1600–2500). Excessive sensor noise can sometimes degrade inter-image alignment, but this did not appear to be the case at these ISO values. For some models, Fried et al were able to operate the turntable continuously at 1 rpm while making 1/50- or 1/25-second exposures every 0.5–1.0 seconds. However, crossed polarisers on the lens and ring light were used when necessary to control specular reflections, and this procedure required longer exposures (e.g. ¼–1/10 seconds) and, hence, manual stepping of the turntable.

 

Greater Argonaut, Argonauta argo. Model SC-363 of the Harvard Museum of Comparative Zoology Collection of Blaschka Marine Invertebrates (length about 7 cm). Fried et al. (2020).

Among the many different software packages currently available, Fried et al. used Agisoft Photoscan (recently updated and renamed Metashape). This software is affordable, completes the processing locally and has a good user interface that allows the user to control the separate processing steps in a manner suitable for this work. The software is used on a Dell Precision Mobile Workstation M4800 with 32 GB of RAM, an Intel Core i7-4910MQ Processor running at 2.9 GHz, and an NVIDIA Quadro K2100M Graphics card with a clock rate of 666 MHz.

 

Blue Button Jellyfish, Porpita porpita. Model SC-138 of the Harvard Museum of Comparative Zoology Collection of Blaschka Marine Invertebrates (diameter about 7 cm). Fried et al. (2020).

Key factors that affect processing time are the number of photos, the number of pixels in the unmasked portion of each photo, and the required accuracy level. The most challenging step in the photogrammetry, but not necessarily the most time-consuming, was always the inter-photo alignment. For several models, Fried et al. included alignment targets off the model at the edge of the turntable. These were useful as long as the model’s orientation on the turntable remained unchanged. To align photos of a given model in multiple orientations, in one case Fried et al. created separate partial digital models 'chunks' in the Agisoft nomenclature, for each orientation and then merged the chunks. In other cases, Fried et al. used the off-model alignment targets in one orientation and masked them in others to achieve a successful alignment. In any event, the software occasionally failed to align or created erroneous alignments due to accumulated small errors. Solving these cases involved various combinations of (a) adding more photos, (b) removing selected photos, (c) reordering photos, and (d) sequential re-alignments of subsets of photos. The highest-accuracy mode, which also is the most time-consuming, was usually required to successfully align the large number of photographs.

 

Football Sea Squirt, Diazona violacea. Model SC-418 of the Harvard Museum of Comparative Zoology Collection of Blaschka Marine Invertebrates (width about 9 cm). The high definition of the digital model results from a mesh made from a computerised tomography scan. This was aligned and merged in Agisoft Metashape with a mesh made from 699 photographs. The combined mesh was then textured from the photos. Fried et al. (2020).

There were some glass models for which even the techniques described above would not yield satisfactory results. Typically, these combine complex design with hidden or partially hidden surfaces, transparent or semi-transparent sections, and/or significant specular reflecting surfaces. For these glass models, Fried et al.  generated an X-ray computed-tomography scan that would be combined with a photogrammetry scan of the same specimen. 3D reconstruction from computed-tomography data has been extensively developed for metrology and biomedical applications.

 

Partial reconstructions of the Football Sea Squirt, Diazona violacea. (a) The reconstruction created by using only X-ray data, and (b) the reconstruction created by using only photographic data. Fried et al. (2020).

For computed-tomography scanning, Fried et al. mounted the glass model on an archival foam block, stabilizing it with Parafilm strips wrapped around archival cotton pads. We scanned the model using a Bruker Skyscan 1173 Micro-Computed Tomography Scanner, with a source voltage of 105 kV and a source current of 60 μA. Fried et al. interposed a 1.0 mm aluminum filter to reduce scatter artifacts in the final model.

 

Blaschka Sea Cucumber. Model SC174 of the Harvard Museum of Comparative Zoology Collection of Blaschka Marine Invertebrates. This is a roughly 7-inch glass model of a Sea Cucumber, Sporadipus tremula. The glass model is one of thousands done by the father-and-son team Rudolf and Leopold Blaschka in the late 1800s. Peter Fried/Sketchfab.

For reconstruction of the computed-tomography scan (creating slice images) and 3D model building, Fried et al. used NRecon and CTAn, respectively (each is part of the Bruker '3D.SUITE' software package). The slice images went through an initial thresholding step to separate the model from the background, a de-speckling step aimed at further reducing noise, and a model-creation step that resulted in an STL surface model file. Finally, in Meshlab, Fried et al. manually removed islands of artifact noise before downsampling (for ease of use) using Quadric Edge Collapse Decimation.

 

Blaschka Nudibranch, Red-Finger Aeolis, swimming. Model B-370, the Red-Finger Aeolis, Flabellina veruccosa, a Nudibranch, of the Cornell University Collection of Blaschka Marine Invertebrates. The Red-Finger Aeolis has been spotted in the Salish Sea (off Washington State). This is a roughly 4-inch glass model of a similar-sized Marine Invertebrate. The glass model is one of thousands done by the father-and-son team Rudolf and Leopold Blaschka in the late 1800s. Originally made as educational models, they are now in collections in over 50 institutions around the world. Peter Fried/Sketchfab.

The greatest challenges encountered during the micro-computed-tomography scan and reconstruction were attributable to the very thin and relatively radiotransparent glass of the Blaschka models. Several scanning attempts were required to achieve a set of slice images in which the model could be cleanly thresholded from the background. After even the best of these attempts, several levels of noise reduction were necessary.

 

Blaschka Vilella – By-the-wind Sailor. Model B-221, By-the-wind Sailor, of the Cornell University Collection of Blaschka Marine Invertebrates. The classification is: Phylum: Cnidaria, Class: Hydrozoa, Order: Anthoathecata, Family: Porpitidae, Genus: Vilella, species: vilella. By-the-wind Sailor is a free-floating colony of |Hydroids that, with a stiff upright 'sail', is blown about on the surface of the open ocean. They eat plankton and often are found stranded on the Northwest coasts of North America. This roughly 4-inch glass model is one of thousands done by the father-and-son team Rudolf and Leopold Blaschka in the late 1800s. Originally made as educational models, they are now in collections in over 50 institutions around the world. Major collections are at Cornell, the Corning Glass Museum, Harvard and University College, Dublin. The model was made from 310 photographs. Photogrammetry with Agisoft Photoscan and touch-up applied in Blender. Peter Fried/Sketchfab.

For some complex models, the mesh can be defined entirely by the X-ray computed-tomography data. Any surface coloring, however, such as that in the texture file, must be provided by photographic data. For other models, certain parts of the structure are made of paint and other filler materials, which are radiotransparent. These parts must be defined with photogrammetry meshes that are then merged with the X-ray-generated sections.

 

Blaschka Sea Anemone. Model SC64 of the Harvard Museum of Comparative Zoology Collection of Blaschka Marine Invertebrates. This is an approximately 3.5-inch glass model of a Sea Anemone, Tealia crassicornis var. purpurea. The glass model is one of thousands done by the father-and-son team Rudolf and Leopold Blaschka in the late 1800s. Originally made as educational models, they are now in collections in over 50 institutions including Cornell, the Corning Glass Museum, Harvard and University College, Dublin. The model was made from 312 photographs with processing by Agisoft Photoscan and touch-up in Blender. The white arms were a challenge, both due to their frosted, semi-transparent glass and also to the thick cross sections which hid many of the surfaces. Peter Fried/Sketchfab.

Some models required no additional work after the mesh and texture files were completed. Others, however, required post-processing, which was done with Blender. The 'Sculpt' mode in Blender provides tools for smoothing portions of the mesh, removing distortions and improving the definition of narrow crevices. Blender can also be used to divide the mesh into sections of different materials (defined by the.mtl files). This allows for different levels of transparency and translucence, albedo, roughness and surface gloss.

 

Blaschka Nudibranch. Model SC-308 of the Harvard Museum of Comparative Zoology Collection of Blaschka Marine Invertebrates. This is a glass model (length about 3.5 inches) of a Nudibranch (originally listed as Pterogasteron marginata, currently known as Elysia marginata). The Nudibrancia, an order in the subclass of sea slugs, include more than 3000 species, of widely varying appearance and colour. This model is one of thousands made by Rudolf and Leopold Blaschka as educational models in the late 1800s. The light-colored material on the bottom of the model is residual epoxy, used to affix a mounting wire for exhibit in decades past. The thin dorsal fins were a challenge to mesh, requiring 528 photographs shot in 7 orientations. The processing was done with Agisoft Photoscan and the surface was post-processed with Blender. Peter Fried/Sketchfab.

Once post-processing was complete the 3D files were uploaded to the SketchFab viewer where, after adding a background and appropriate lighting, Fried et al. adjusted surface qualities of the model. 

Fried et al.'s objective is to demonstrate archival capture of challenging 3D subjects, specifically glossy, translucent and highly detailed and delicate glass models. Much of their workflow optimises well-known techniques of light and polarisation control and photogrammetric processing. Significantly, we have also merged photogrammetry and computed-tomography data to create meshes of intricate structures made of multiple materials including glass.

 

Blaschka Cuttlefish. Model SC-369 of the Harvard Museum of Comparative Zoology Collection of Blaschka Marine Invertebrates. This glass model is one of thousands made by Rudolf and Leopold Blaschka in the late 1800s as educational models. This species of Cuttlefish (labeled by the Blaschkas as Sepia bisserialis, but currently known as Sepia elegans), never larger than about 3.5 inches, is found in the Mediterranean and in the Eastern Atlantic from Scotland in the north to the west coast of Africa in the south. The 3D model was made from 365 photographs using Agisoft Photoscan. In addition to glass the Blaschkas used other materials. For this Cuttlefish the dorsal surface was made of painted paper. This thin surface posed a challenge for the photogrammetry alignment and required careful masking of the photos prior to processing. Blender was used to assign four sets of material properties to the dorsal area, the remainder of the body, the tentacle and the eyes. Peter Fried/Sketchfab.

Recently, software and cameras have become available with automated focus stacking. This feature holds promise for some combination of higher resolution, larger effective depth of field and shorter individual exposures, but only if the processing load  for 250–700 separate photos is manageable.

 

Blaschka Sea Cucumber. Model SC168 of the Harvard Museum of Comparative Zoology Collection of Blaschka Marine Invertebrates. This is a roughly 5-inch glass model of a Sea Cucumber, Holothuria maculata. The glass model is one of thousands done by the father-and-son team Rudolf and Leopold Blaschka in the late 1800s. Originally made as educational models, they are now in collections in over 50 institutions around the world. Major collections are at Cornell, the Corning Glass Museum, Harvard and University College, Dublin. The 3D model was made from about 200 photographs taken at the Museum of Comparative Zoology. The photogrammetry processing was done with Agisoft Photoscan and minor touch-up was applied in Blender. Peter Fried/Sketchfab.

Future work should (a) identify ways to improve efficiency and resolution through focus stacking; (b) develop further use of computed-tomography scanning, especially for imaging highly transparent glassworks (e.g. Blaschka Jellyfish); and (c) explore the utility of voxel-based processing for digitising such objects. The use of these additional techniques, as well as those demonstrated so far, should expand the universe of objects suitable for 3D digitisation.

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