scholarly journals Quantifying Surface‐Height Change over a Periglacial Environment with ICESat‐2 Laser Altimetry

2021 ◽  
Author(s):  
R. J. Michaelides ◽  
M. B. Bryant ◽  
M. R. Siegfried ◽  
A. A. Borsa
Keyword(s):  
Laser Altimetry ◽  
Height Change

scholarly journals Subglacial hydrological connectivity within the Byrd Glacier catchment, East Antarctica

2014 ◽  
Vol 60 (220) ◽  
pp. 345-352 ◽  
Author(s):  
A.P. Wright ◽  
D.A. Young ◽  
J.L. Bamber ◽  
J.A. Dowdeswell ◽  
A.J. Payne ◽  
...  
Keyword(s):  
East Antarctica ◽  
Laser Altimetry ◽  
Ice Cloud ◽  
Ice Surface ◽  
New Radio ◽  
Radio Echo Sounding ◽  
Hydraulic Gradients ◽  
Height Change ◽  
Subglacial Lakes ◽  
Along Track

AbstractIce, Cloud and land Elevation Satellite (ICESat) repeat-track laser altimetry has identified 17 sites within the Byrd Glacier catchment, East Antarctica, where rapid ice-surface height changes have occurred, which have been interpreted as evidence for ‘active’ subglacial lakes. Here we present evidence from a new radio-echo sounding (RES) survey at 11 of these locations to understand the bed conditions associated with the proposed hydrological activity. At none of the sites examined did we find evidence in support of substantial pooled basal water. In the majority of cases, along-track RES bed reflection amplitudes either side of the locations of surface height change are indistinguishable from those within the features. These results indicate that, in most cases, hypothesized ‘active’ lakes are not discrete radar targets and are therefore much smaller than the areas of surface height change. In addition, we have identified three new relatively large subglacial lakes upstream of the region where most ‘active’ subglacial lakes are found, in an area where the hydraulic gradient is significantly lower. Our results suggest that substantial and long-lasting basal water storage in the Byrd Glacier catchment occurs only under low hydraulic gradients, while coast-proximal sites of hydraulic activity likely involve small or temporary accumulations of basal water.

scholarly journals Improving InSAR elevation models in Antarctica using laser altimetry, accounting for ice motion, orbital errors and atmospheric delays

2015 ◽  
Vol 162 ◽  
pp. 112-118 ◽  
Author(s):  
Yu Zhou ◽  
Chunxia Zhou ◽  
Fanghui Deng ◽  
Dongchen E ◽  
Haiyan Liu ◽  
...  
Keyword(s):  
Laser Altimetry ◽  
Atmospheric Delays

scholarly journals Clinical, Radiographic, and Histomorphometric Evaluation of a Vertical Ridge Augmentation Procedure Using a Titanium-Reinforced Microporous Expanded Polytetrafluoroethylene Emrane: A Prospective Case Series with 1-Year Follow-Up

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3828
Author(s):  
Jung-Gu Ji ◽  
Jung-A Yu ◽  
Seong-Ho Choi ◽  
Dong-Woon Lee
Keyword(s):  
Case Series ◽  
Graft Material ◽  
Ridge Augmentation ◽  
Expanded Polytetrafluoroethylene ◽  
Implant Placement ◽  
Significant Difference ◽  
Staged Approach ◽  
Height Change ◽  
Prospective Case Series ◽  
Augmentation Procedure

Vertical ridge augmentation for long-term implant stability is difficult in severely resorbed areas. We examined the clinical, radiological, and histological outcomes of guided-bone regeneration using novel titanium-reinforced microporous expanded polytetrafluoroethylene (MP-ePTFE) membranes. Eighteen patients who underwent implant placement using a staged approach were enrolled (period: 2018–2019). Vertical ridge augmentation was performed in areas with vertical bone defects ≥ 4 mm. Twenty-six implant fixtures were placed in 14 patients. At implant placement six fixtures had relatively low stability. On cone-beam computed tomography, the average vertical changes were 4.2 ± 1.9 (buccal), 5.9 ± 2.7 (central), and 4.4 ± 2.8 mm (lingual) at six months after vertical ridge augmentation. Histomorphometric analyses revealed that the average proportions of new bone, residual bone substitute material, and soft tissue were 34.91 ± 11.61%, 7.16 ± 2.74%, and 57.93 ± 11.09%, respectively. Stable marginal bone levels were observed at 1-year post-loading. The residual bone graft material area was significantly lower in the exposed group (p = 0.003). There was no significant difference in the vertical height change in the buccal side between immediately after the augmentation procedure and the implant placement reentry time (p = 0.371). However, all implants functioned well regardless of the exposure during the observation period. Thus, vertical ridge augmentation around implants using titanium-reinforced MP-ePTFE membranes can be successful.

scholarly journals Combined Block Adjustment for Optical Satellite Stereo Imagery Assisted by Spaceborne SAR and Laser Altimetry Data

2021 ◽  
Vol 13 (16) ◽  
pp. 3062
Author(s):  
Guo Zhang ◽  
Boyang Jiang ◽  
Taoyang Wang ◽  
Yuanxin Ye ◽  
Xin Li
Keyword(s):  
Large Scale ◽  
Satellite Image ◽  
Field Measurements ◽  
High Elevation ◽  
Global Scale ◽  
Stereo Image ◽  
Image Process ◽  
Control Points ◽  
Altimetry Data ◽  
Laser Altimetry

To ensure the accuracy of large-scale optical stereo image bundle block adjustment, it is necessary to provide well-distributed ground control points (GCPs) with high accuracy. However, it is difficult to acquire control points through field measurements outside the country. Considering the high planimetric accuracy of spaceborne synthetic aperture radar (SAR) images and the high elevation accuracy of satellite-based laser altimetry data, this paper proposes an adjustment method that combines both as control sources, which can be independent from GCPs. Firstly, the SAR digital orthophoto map (DOM)-based planar control points (PCPs) acquisition is realized by multimodal matching, then the laser altimetry data are filtered to obtain laser altimetry points (LAPs), and finally the optical stereo images’ combined adjustment is conducted. The experimental results of Ziyuan-3 (ZY-3) images prove that this method can achieve an accuracy of 7 m in plane and 3 m in elevation after adjustment without relying on GCPs, which lays the technical foundation for a global-scale satellite image process.

Estimating geoid height change in North America: past, present and future

2011 ◽  
Vol 86 (5) ◽  
pp. 337-358 ◽  
Author(s):  
Thomas Jacob ◽  
John Wahr ◽  
Richard Gross ◽  
Sean Swenson ◽  
Geruo A
Keyword(s):  
North America ◽  
Geoid Height ◽  
Height Change

scholarly journals 2001–2009 elevation and mass losses in the Larsen A and B embayments, Antarctic Peninsula

2011 ◽  
Vol 57 (204) ◽  
pp. 737-754 ◽  
Author(s):  
Christopher A. Shuman ◽  
Etienne Berthier ◽  
Ted A. Scambos
Keyword(s):  
Antarctic Peninsula ◽  
Loss Rate ◽  
Ice Shelf ◽  
Laser Altimetry ◽  
Ice Shelves ◽  
Ice Volume ◽  
Mass Losses ◽  
Digital Elevation ◽  
Modis Imagery ◽  
Elevation Changes

AbstractWe investigate the elevation and mass-balance response of tributary glaciers following the loss of the Larsen A and B ice shelves, Antarctic Peninsula (in 1995 and 2002 respectively). Our study uses MODIS imagery to track ice extent, and ASTER and SPOT5 digital elevation models (DEMs) plus ATM and ICESat laser altimetry to track elevation changes, spanning the period 2001–09. The measured Larsen B tributary glaciers (Hektoria, Green, Evans, Punchbowl, Jorum and Crane) lost up to 160 m in elevation during 2001–06, and thinning continued into 2009. Elevation changes were small for the more southerly Flask and Leppard Glaciers, which are still constrained by a Larsen B ice shelf remnant. In the northern embayment, continued thinning of >3 m a−1 on Drygalski Glacier, 14 years after the Larsen A ice shelf disintegrated, suggests that mass losses for the exposed Larsen B tributaries will continue for years into the future. Grounded ice volume losses exceed 13 km3 for Crane Glacier and 30 km3 for the Hektoria–Green–Evans glaciers. The combined mean loss rate for 2001–06 is at least 11.2 Gt a−1. Our values differ significantly from published mass-budget-based estimates for these embayments, but are a reasonable fraction of GRACE-derived rates for the region (∼40 Gt a−1).

Topography of the Northern Hemisphere of Mercury from MESSENGER Laser Altimetry

Science ◽  
2012 ◽  
Vol 336 (6078) ◽  
pp. 217-220 ◽  
Author(s):  
M. T. Zuber ◽  
D. E. Smith ◽  
R. J. Phillips ◽  
S. C. Solomon ◽  
G. A. Neumann ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Laser Altimetry

Optische Schmelzbadüberwachung*/Optical monitoring of the melting bath in an Al-melting furnace

2018 ◽  
Vol 108 (11-12) ◽  
pp. 760-766
Author(s):  
S. Mohammadifard ◽  
J. Langner ◽  
M. Stonis ◽  
S. Sauke ◽  
H. Larki Harchegani ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Optical Sensors ◽  
Melting Furnace ◽  
Bath Surface ◽  
Optical Monitoring ◽  
Measuring Systems ◽  
Height Change ◽  
First Time ◽  
Contact Sensors ◽  
Holding Temperature

In einem Aluminium (Al)-Schmelzofen sind der Füllstand des Schmelzbades und die Oxidschichtmenge mit Kontaktsensoren nicht überwachbar, da das Schmelzbad aufgrund der hohen Haltebereich-Temperaturen von über 600 °C nicht zugänglich ist. Deshalb wird ein Online-Überwachungssystem des Aluminium-Schmelzbades mithilfe optischer Sensoren erforscht. Dafür wird das Schmelzbad mit geeigneten optischen Messsystemen identifiziert. Schließlich werden durch Bildanalyse-Algorithmen die Höhenänderung der Schmelze herausgearbeitet. Zudem werden Oxidschichten im Ofen auf der Badoberfläche mithilfe der Algorithmen detektiert.   The melt level and oxide layer quantity in an aluminum melting furnace cannot be monitored by contact sensors, since the melting bath is not accessible due to the high holding temperature (above 600 °C). Therefore, the method of monitoring the melting bath by means of optical sensors is investigated for the first time. For this purpose, suitable optical measuring systems can be applied which will be able to record the melting bath. The height change of the melt is to be elaborated by means of image analysis and any oxide layer on the bath surface is to be detected.

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