Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016–2017
ABSTRACT We present a workflow to track icebergs in proglacial fjords using oblique time-lapse photos and the Lucas-Kanade optical flow algorithm. We employ the workflow at LeConte Bay, Alaska, where we ran five time-lapse cameras between April 2016 and September 2017, capturing more than 400 000 ph...
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Language: | English |
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Cambridge University Press (CUP)
2019
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Online Access: | http://dx.doi.org/10.1017/jog.2018.105 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143018001053 |
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crcambridgeupr:10.1017/jog.2018.105 2024-09-15T18:15:39+00:00 Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016–2017 KIENHOLZ, CHRISTIAN AMUNDSON, JASON M. MOTYKA, ROMAN J. JACKSON, REBECCA H. MICKETT, JOHN B. SUTHERLAND, DAVID A. NASH, JONATHAN D. WINTERS, DYLAN S. DRYER, WILLIAM P. TRUFFER, MARTIN 2019 http://dx.doi.org/10.1017/jog.2018.105 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143018001053 en eng Cambridge University Press (CUP) http://creativecommons.org/licenses/by/4.0/ Journal of Glaciology volume 65, issue 250, page 195-211 ISSN 0022-1430 1727-5652 journal-article 2019 crcambridgeupr https://doi.org/10.1017/jog.2018.105 2024-07-31T04:04:45Z ABSTRACT We present a workflow to track icebergs in proglacial fjords using oblique time-lapse photos and the Lucas-Kanade optical flow algorithm. We employ the workflow at LeConte Bay, Alaska, where we ran five time-lapse cameras between April 2016 and September 2017, capturing more than 400 000 photos at frame rates of 0.5–4.0 min −1 . Hourly to daily average velocity fields in map coordinates illustrate dynamic currents in the bay, with dominant downfjord velocities (exceeding 0.5 m s −1 intermittently) and several eddies. Comparisons with simultaneous Acoustic Doppler Current Profiler (ADCP) measurements yield best agreement for the uppermost ADCP levels (~ 12 m and above), in line with prevalent small icebergs that trace near-surface currents. Tracking results from multiple cameras compare favorably, although cameras with lower frame rates (0.5 min −1 ) tend to underestimate high flow speeds. Tests to determine requisite temporal and spatial image resolution confirm the importance of high image frame rates, while spatial resolution is of secondary importance. Application of our procedure to other fjords will be successful if iceberg concentrations are high enough and if the camera frame rates are sufficiently rapid (at least 1 min −1 for conditions similar to LeConte Bay). Article in Journal/Newspaper Journal of Glaciology Alaska Cambridge University Press Journal of Glaciology 65 250 195 211 |
institution |
Open Polar |
collection |
Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
description |
ABSTRACT We present a workflow to track icebergs in proglacial fjords using oblique time-lapse photos and the Lucas-Kanade optical flow algorithm. We employ the workflow at LeConte Bay, Alaska, where we ran five time-lapse cameras between April 2016 and September 2017, capturing more than 400 000 photos at frame rates of 0.5–4.0 min −1 . Hourly to daily average velocity fields in map coordinates illustrate dynamic currents in the bay, with dominant downfjord velocities (exceeding 0.5 m s −1 intermittently) and several eddies. Comparisons with simultaneous Acoustic Doppler Current Profiler (ADCP) measurements yield best agreement for the uppermost ADCP levels (~ 12 m and above), in line with prevalent small icebergs that trace near-surface currents. Tracking results from multiple cameras compare favorably, although cameras with lower frame rates (0.5 min −1 ) tend to underestimate high flow speeds. Tests to determine requisite temporal and spatial image resolution confirm the importance of high image frame rates, while spatial resolution is of secondary importance. Application of our procedure to other fjords will be successful if iceberg concentrations are high enough and if the camera frame rates are sufficiently rapid (at least 1 min −1 for conditions similar to LeConte Bay). |
format |
Article in Journal/Newspaper |
author |
KIENHOLZ, CHRISTIAN AMUNDSON, JASON M. MOTYKA, ROMAN J. JACKSON, REBECCA H. MICKETT, JOHN B. SUTHERLAND, DAVID A. NASH, JONATHAN D. WINTERS, DYLAN S. DRYER, WILLIAM P. TRUFFER, MARTIN |
spellingShingle |
KIENHOLZ, CHRISTIAN AMUNDSON, JASON M. MOTYKA, ROMAN J. JACKSON, REBECCA H. MICKETT, JOHN B. SUTHERLAND, DAVID A. NASH, JONATHAN D. WINTERS, DYLAN S. DRYER, WILLIAM P. TRUFFER, MARTIN Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016–2017 |
author_facet |
KIENHOLZ, CHRISTIAN AMUNDSON, JASON M. MOTYKA, ROMAN J. JACKSON, REBECCA H. MICKETT, JOHN B. SUTHERLAND, DAVID A. NASH, JONATHAN D. WINTERS, DYLAN S. DRYER, WILLIAM P. TRUFFER, MARTIN |
author_sort |
KIENHOLZ, CHRISTIAN |
title |
Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016–2017 |
title_short |
Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016–2017 |
title_full |
Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016–2017 |
title_fullStr |
Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016–2017 |
title_full_unstemmed |
Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016–2017 |
title_sort |
tracking icebergs with time-lapse photography and sparse optical flow, leconte bay, alaska, 2016–2017 |
publisher |
Cambridge University Press (CUP) |
publishDate |
2019 |
url |
http://dx.doi.org/10.1017/jog.2018.105 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143018001053 |
genre |
Journal of Glaciology Alaska |
genre_facet |
Journal of Glaciology Alaska |
op_source |
Journal of Glaciology volume 65, issue 250, page 195-211 ISSN 0022-1430 1727-5652 |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1017/jog.2018.105 |
container_title |
Journal of Glaciology |
container_volume |
65 |
container_issue |
250 |
container_start_page |
195 |
op_container_end_page |
211 |
_version_ |
1810453587650674688 |