Photogrammetric Maps of a Volcanic Eruption Area, Deception Island, Antarctica

On cover: "RF 3861."The volcanic Deception Island, Antarctica, has erupted three times since 1967. Three maps are presented which display topographic changes of the most affected part of the island. The fourth map represents a crater in the terminus of a cirque glacier which has been recently examined. Procedures used in preparing the maps are discussed.Office of Polar Programs, National Science Foundation, Grant No. GV-41368

Structure-From-Motion Photogrammetry of Antarctic Historical Aerial Photographs in Conjunction with Ground Control Derived from Satellite Data

A longer temporal scale of Antarctic observations is vital to better understanding glacier dynamics and improving ice sheet model projections. One underutilized data source that expands the temporal scale is aerial photography, specifically imagery collected prior to 1990. However, processing Antarctic historical aerial imagery using modern photogrammetry software is difficult, as it requires precise information about the data collection process and extensive in situ ground control is required. Often, the necessary orientation metadata for older aerial imagery is lost and in situ data collection in regions like Antarctica is extremely difficult to obtain, limiting the use of traditional photogrammetric methods. Here, we test an alternative methodology to generate elevations from historical Antarctic aerial imagery. Instead of relying on pre-existing ground control, we use structure-from-motion photogrammetry techniques to process the imagery with manually derived ground control from high-resolution satellite imagery. This case study is based on vertical aerial image sets collected over Byrd Glacier, East Antarctica in December 1978 and January 1979. Our results are the oldest, highest resolution digital elevation models (DEMs) ever generated for an Antarctic glacier. We use these DEMs to estimate glacier dynamics and show that surface elevation of Byrd Glacier has been constant for the past ∼40 years

Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Wintering at Byrd Station

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Analysis of the Byrd Station Strain Net, Antarctica

On cover: RF 2500.This report presents some results of field investigations relating to the study of glacier flow in Marie Byrd Land, Antarctica. The physical quantities necessary for a solution to the problem of the mode of flow of the continental ice sheet in the Ross glacial drainage basin are being sought by several principal lines of investigation: determination of surface strain rate and surface slope by analysis of precise surveys of the Byrd Station Strain Net that have been carried out by the Topographic Branch of the U.S. Geological Survey; determination of strain rate and temperature distribution at depth in the deep hole at Byrd Station drilled by the U.S. Army Cold Regions Research and Engineering Laboratory; determination of ice thickness and of glacier bed configuration and conditions by geophysical exploration, including seismic, gravimetric, magnetic and radio-echo sounding methods; analysis of the structure and dynamic physical properties of ice; and observation of snow deposition and metamorphosis and surface morphology in order to explain parts of the core from Byrd Station deep drill hole, and estimate the mass balance. Much of the material presented in the report is based upon observations made by field parties which were based at Byrd Station and operated in the region of the Byrd Station Strain Net, which lies between Byrd Station and the Ross-Amundsen ice divide, during the austral summers of 1967-68, 1969-70, 1971-72, and 1973-74.National Science Foundation Grants GA-1141, GA-14425 and GV-26137X

Structure-From-Motion Photogrammetry of Antarctic Historical Aerial Photographs in Conjunction with Ground Control Derived from Satellite Data

A longer temporal scale of Antarctic observations is vital to better understanding glacier dynamics and improving ice sheet model projections. One underutilized data source that expands the temporal scale is aerial photography, specifically imagery collected prior to 1990. However, processing Antarctic historical aerial imagery using modern photogrammetry software is difficult, as it requires precise information about the data collection process and extensive in situ ground control is required. Often, the necessary orientation metadata for older aerial imagery is lost and in situ data collection in regions like Antarctica is extremely difficult to obtain, limiting the use of traditional photogrammetric methods. Here, we test an alternative methodology to generate elevations from historical Antarctic aerial imagery. Instead of relying on pre-existing ground control, we use structure-from-motion photogrammetry techniques to process the imagery with manually derived ground control from high-resolution satellite imagery. This case study is based on vertical aerial image sets collected over Byrd Glacier, East Antarctica in December 1978 and January 1979. Our results are the oldest, highest resolution digital elevation models (DEMs) ever generated for an Antarctic glacier. We use these DEMs to estimate glacier dynamics and show that surface elevation of Byrd Glacier has been constant for the past &sim;40 years