scholarly journals PyTrx: A Python toolbox for deriving velocities, surface areas and line measurements from oblique imagery in glacial environments

2018 ◽  
Author(s):  
Penelope How ◽  
Nicholas R. J. Hulton ◽  
Lynne Buie
Keyword(s):  
Projective Transformation ◽  
Time Lapse ◽  
Transformation Model ◽  
Ice Flow ◽  
Surface Areas ◽  
Supraglacial Lakes ◽  
Glacier Terminus ◽  
Glacial Environments ◽  
Spatio Temporal ◽  
Flow Velocities

Abstract. Terrestrial time-lapse photogrammetry is a rapidly growing method for deriving measurements from glacial environments because it provides high spatio-temporal resolution records of change. However, glacial photogrammetry toolboxes are limited currently. Without prior knowledge in photogrammetry and computer coding, they are used primarily to calculate ice flow velocities or to serve as qualitative records. PyTrx (available at https://github.com/PennyHow/PyTrx) is presented here as a Python-alternative toolbox to widen the range of photogrammetry toolboxes on offer to the glaciology community. The toolbox holds core photogrammetric functions for point seeding, feature-tracking, image registration, and georectification (using a planar projective transformation model). In addition, PyTrx facilitates areal and line measurements, which can be detected from imagery using either an automated or manual approach. Examples of PyTrx's applications are demonstrated using time-lapse imagery from Kronebreen and Tunabreen, two tidewater glaciers in Svalbard. Products from these applications include ice flow velocities, surface areas of supraglacial lakes and meltwater plumes, and glacier terminus profiles.

scholarly journals PyTrx: a Python-based monoscopic terrestrial photogrammetry toolset for glaciology

2020 ◽  
Author(s):  
Penelope How ◽  
Nicholas Hulton ◽  
Lynne Buie ◽  
Douglas Benn
Keyword(s):  
Projective Transformation ◽  
Image Data ◽  
Time Lapse ◽  
Object Identification ◽  
Transformation Model ◽  
Surface Areas ◽  
Glacier Terminus ◽  
Spatio Temporal ◽  
Tracking Object ◽  
Terrestrial Photogrammetry

<p>Terrestrial photogrammetry is a growing method for deriving measurements from contemporary and historical imagery of glacial environments, providing unique insights into glacier change at a high spatio-temporal resolution. However, the potential usefulness of terrestrial image data is currently limited by the unavailability of user-friendly toolsets that contain all the photogrammetry processes required. PyTrx is presented here as a Python-alternative toolset to widen the range of monoscopic photogrammetry (i.e. from a single viewpoint) toolsets on offer to the glaciology community. The toolset holds core photogrammetric functions for template generation, feature-tracking, object identification, image registration, and georectification (using a planar projective transformation model), which can be performed on both contemporary and historical imagery. Examples of PyTrx's applications are demonstrated using contemporary time-lapse imagery, including ice flow velocities, surface areas of supraglacial lakes and meltwater plumes, and glacier terminus profiles.</p>

scholarly journals Development and application of a time-lapse photograph analysis method to investigate the link between tidewater glacier flow variations and supraglacial lake drainage events

2013 ◽  
Vol 59 (214) ◽  
pp. 287-302 ◽  
Author(s):  
Brad Danielson ◽  
Martin Sharp
Keyword(s):  
Time Lapse ◽  
Velocity Variation ◽  
Lake Area ◽  
Flow Acceleration ◽  
Supraglacial Lakes ◽  
Glacier Terminus ◽  
Tidewater Glacier ◽  
Glacier Flow ◽  
Lake Drainage ◽  
Time Lapse Photography

AbstractMarine-terminating glaciers may experience seasonal and short-term flow variations, which can impact rates of ice flux through the glacier terminus. We explore the relationship between variability in the flow of a large tidewater glacier (Belcher Glacier, Nunavut, Canada), the seasonal cycle of surface meltwater production and the rapid drainage of supraglacial lakes. We demonstrate a novel method for analyzing time-lapse photography to quantify lake area change rates (a proxy for net filling and drainage rates) and develop a typology of lake drainage styles. GPS records of ice motion reveal four flow acceleration events which can be linked to lake drainage events discovered in the time-lapse photography. These events are superimposed on a longer pattern of velocity variation that is linked to seasonal variation in surface melting. At the terminus of the glacier, the ice displacement associated with the lake drainage events constitutes ∼10% of the seasonally accelerated displacement or 0.4% of the total annual ice displacement (336 m a−1). While the immediate ice response to these individual perturbations may be small, these drainage events may enhance overall seasonal acceleration by opening and/or sustaining meltwater conduits to the glacier bed.

scholarly journals Ice flow velocities over Vostok Subglacial Lake, East Antarctica, determined by 10 years of GNSS observations

2013 ◽  
Vol 59 (214) ◽  
pp. 315-326 ◽  
Author(s):  
A. Richter ◽  
D.V. Fedorov ◽  
M. Fritsche ◽  
S.V. Popov ◽  
V.Ya. Lipenkov ◽  
...  
Keyword(s):  
Flow Velocity ◽  
East Antarctica ◽  
Global Navigation Satellite Systems ◽  
Steady Increase ◽  
Lake Area ◽  
Ice Flow ◽  
Satellite Systems ◽  
Subglacial Lake ◽  
Gnss Observations ◽  
Flow Velocities

AbstractRepeated Global Navigation Satellite Systems (GNSS) observations were carried out at 50 surface markers in the Vostok Subglacial Lake (East Antarctica) region between 2001 and 2011. The horizontal ice flow velocity vectors were derived with accuracies of 1 cm a−1 and 0.5°, representing the first reliable information on ice flow kinematics in the northern part of the lake. Within the lake area, ice flow velocities do not exceed 2 m a−1. The ice flow azimuth is southeast in the southern part of the lake and turns gradually to east-northeast in the northern part. In the northern part, as the ice flow enters the lake at the western shore, the velocity decreases towards the central lake axis, then increases slightly past the central axis. In the southern part, a continued acceleration is observed from the central lake axis across the downstream grounding line. Based on the observed flow velocity vectors and ice thickness data, mean surface accumulation rates are inferred for four surface segments between Ridge B and Vostok Subglacial Lake and show a steady increase towards the north.

scholarly journals Ice-flow and mass changes of Lewis Glacier, Mount Kenya, East Africa, 1986–90: observations and modeling

1992 ◽  
Vol 38 (128) ◽  
pp. 36-42
Author(s):  
Stefan Hastenrath
Keyword(s):  
Time Interval ◽  
Volume Loss ◽  
Climatic Forcing ◽  
Ice Flow ◽  
Mass Budget ◽  
Modeling And Prediction ◽  
Mass Redistribution ◽  
Glacier Changes ◽  
Flow Velocities

AbstractThe long-term monitoring of Lewis Glacier on Mount Kenya serves as a basis for the study of glacier evolution in response to climatic forcing through modeling of its ice flow and mass budget. Following up on an earlier modeling and prediction study to 1990, this paper examines the ice-mass and flow changes in relation to the net-balance conditions over 1986–90. A model experiment using as climatic forcing the observed 1978–86 vertical net-balance profile yielded a volume loss and slow down of ice flow more drastic than observed during 1986–90. The causes of this discrepancy were examined in successive model experiments. Realistic simulations of mass-budget and thickness changes over 1986–90 are obtained using as input the net-balance forcing for the same period rather than for the preceding 1978–86 interval, and approximate flow velocities. With the same net-balance forcing and a completely stagnant Lewis Glacier, the elimination of mass redistribution by ice flow acts to mitigate the loss of volume and thickness in the upper glacier, and to accentuate it in the lower glacier. Accordingly, the observed 1986–90 net-balance profile along with the 1990 ice-flow velocities provide suitable input for the modeling of Lewis Glacier changes to 1994. Under continuation of the 1986–90 climatic forcing, ice thinning ranging from less than 1 m in the upper glacier to more than 7 m in the lower glacier, and a total volume loss of order 57 × 104 m3, are anticipated over the 1990–94 time interval.

scholarly journals Dissolved and Particulate Organic Carbon in Icelandic Proglacial Streams: A First Estimate

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 748 ◽  
Author(s):  
Peter Chifflard ◽  
Christina Fasching ◽  
Martin Reiss ◽  
Lukas Ditzel ◽  
Kyle S. Boodoo
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Ice Cap ◽  
Glacier Terminus ◽  
Fluorescence Measurements ◽  
Sampling Locations ◽  
Carbon Release ◽  
Annual Carbon ◽  
Spatio Temporal

Here for the first time, we analyze the concentration of dissolved (DOC) and particulate organic carbon (POC), as well as its optical properties (absorbance and fluorescence) from several proglacial streams across Iceland, the location of Europe’s largest non-polar ice cap. We found high spatial variability of DOC concentrations and dissolved organic matter (DOM) composition during peak melt, sampling 13 proglacial streams draining the 5 main Icelandic glaciers. Although glacial-derived organic matter (OM) was dominated by proteinaceous florescence, organic matter composition was variable among glaciers, often exhibiting relatively higher aromatic content and increased humification (based on absorbance and fluorescence measurements) closer to the glacier terminus, modulated by the presence of glacial lakes. Additional sampling locations the in flow path of the river Hvitá revealed that while POC concentrations decreased downstream, DOC concentrations and the autochthonous fraction of OM increased, suggesting the reworking of the organic carbon by microbial communities, with likely implications for downstream ecosystems as glaciers continue to melt. Based on our measured DOC concentrations ranging from 0.11 mg·L−1 to 0.94 mg·L−1, we estimate a potential annual carbon release of 0.008 ± 0.002 Tg·C·yr−1 from Icelandic glaciers. This non-conservative first estimate serves to highlight the potentially significant contribution of Icelandic pro-glacial streams to the global carbon cycle and the need for the quantification and determination of the spatio-temporal variation of DOC and POC fluxes and their respective drivers, particularly in light of increased rates of melting due to recent trends in climatic warming.

Nonlinear Image Mosaic of Pipe Inner Surface

2013 ◽  
Vol 427-429 ◽  
pp. 1620-1624
Author(s):  
Jun Wei Bao ◽  
Qiang Chen ◽  
Fu Qiang Peng
Keyword(s):  
Imaging System ◽  
Projective Transformation ◽  
Transformation Model ◽  
Image Mosaic ◽  
Panoramic Imaging ◽  
Mosaic Image ◽  
Quadratic Interpolation ◽  
Inner Surface ◽  
Left Image ◽  
Traditional Image

The present study is concerned about image mosaic in single reflector panoramic imaging system (SRPIS). A nonlinear image mosaic algorithm is proposed to get the panoramic image of pipe inner surface. Because of nonlinear distortion in the images which are unwrapped from the original images, its practically impossible for traditional image mosaic method based on 2D planar projective transformation to eliminate phenomenon of ghost and blur in the seam. Nonlinear image mosaic algorithm is performed by projecting many pieces of image divided from right image onto the left image. The position-variant parameters of transformation model are got by quadratic interpolation. The results show that nonlinear image mosaic algorithm overcomes the limitations of traditional image mosaic method in images with distortion and the mosaic image is clearer than that by traditional image mosaic method.

scholarly journals Ice-flow and mass changes of Lewis Glacier, Mount Kenya, East Africa, 1986–90: observations and modeling

1992 ◽  
Vol 38 (128) ◽  
pp. 36-42 ◽  
Author(s):  
Stefan Hastenrath
Keyword(s):  
Time Interval ◽  
Volume Loss ◽  
Climatic Forcing ◽  
Ice Flow ◽  
Mass Budget ◽  
Modeling And Prediction ◽  
Mass Redistribution ◽  
Glacier Changes ◽  
Flow Velocities

AbstractThe long-term monitoring of Lewis Glacier on Mount Kenya serves as a basis for the study of glacier evolution in response to climatic forcing through modeling of its ice flow and mass budget. Following up on an earlier modeling and prediction study to 1990, this paper examines the ice-mass and flow changes in relation to the net-balance conditions over 1986–90. A model experiment using as climatic forcing the observed 1978–86 vertical net-balance profile yielded a volume loss and slow down of ice flow more drastic than observed during 1986–90. The causes of this discrepancy were examined in successive model experiments. Realistic simulations of mass-budget and thickness changes over 1986–90 are obtained using as input the net-balance forcing for the same period rather than for the preceding 1978–86 interval, and approximate flow velocities. With the same net-balance forcing and a completely stagnant Lewis Glacier, the elimination of mass redistribution by ice flow acts to mitigate the loss of volume and thickness in the upper glacier, and to accentuate it in the lower glacier. Accordingly, the observed 1986–90 net-balance profile along with the 1990 ice-flow velocities provide suitable input for the modeling of Lewis Glacier changes to 1994. Under continuation of the 1986–90 climatic forcing, ice thinning ranging from less than 1 m in the upper glacier to more than 7 m in the lower glacier, and a total volume loss of order 57 × 104m3, are anticipated over the 1990–94 time interval.

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