Accurate Bathymetric Maps From Underwater Digital Imagery Without Ground Control
Structure-from-Motion (SfM) photogrammetry can be used with digital underwater photographs to generate high-resolution bathymetry and orthomosaics with millimeter-to-centimeter scale resolution at relatively low cost. Although these products are useful for assessing species diversity and health, the...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2020-06-01
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| Series: | Frontiers in Marine Science |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/article/10.3389/fmars.2020.00525/full |
| _version_ | 1818120363451613184 |
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| author | Gerald A. Hatcher Jonathan A. Warrick Andrew C. Ritchie Evan T. Dailey David G. Zawada Christine Kranenburg Kimberly K. Yates |
| author_facet | Gerald A. Hatcher Jonathan A. Warrick Andrew C. Ritchie Evan T. Dailey David G. Zawada Christine Kranenburg Kimberly K. Yates |
| author_sort | Gerald A. Hatcher |
| collection | DOAJ |
| description | Structure-from-Motion (SfM) photogrammetry can be used with digital underwater photographs to generate high-resolution bathymetry and orthomosaics with millimeter-to-centimeter scale resolution at relatively low cost. Although these products are useful for assessing species diversity and health, they have additional utility for quantifying benthic community structure, such as coral growth and fine-scale elevation change over time, if accurate length scales and georeferencing are included. This georeferencing is commonly provided with “ground control,” such as pre-installed seafloor benchmarks or identifiable “static” features, which can be difficult and time consuming to install, survey, and maintain. To address these challenges, we developed the SfM Quantitative Underwater Imaging Device with Five Cameras (SQUID-5), a towed surface vehicle with an onboard survey-grade Global Navigation Satellite System (GNSS) and five rigidly mounted downward-looking cameras with overlapping views of the seafloor. The cameras are tightly synchronized with both the GNSS and each other to collect quintet photo sets and record the precise location of every collection event. The system was field tested in July 2019 in the U.S. Florida Keys, in water depths ranging from 3 to 9 m over a variety of bottom types. Surveying accuracy was assessed using pre-installed stations with known coordinates, machined scale bars, and two independent surveys of a site to evaluate repeatability. Under a range of sea conditions, ambient lighting, and water clarity, we were able to map living and senile coral reef habitats and sand waves at mm-scale resolution. Data were processed using best practice SfM techniques without ground control and local measurement errors of horizontal and vertical scales were consistently sub-millimeter, equivalent to 0.013% RMSE relative to water depth. Survey-to-survey repeatability RMSE was on the order of 3 cm without georeferencing but could be improved to several millimeters with the incorporation of one or more non-surveyed marker points. We demonstrate that the SQUID-5 platform can map complex coral reef and other seafloor habitats and measure mm-to-cm scale changes in the morphology and location of seafloor features over time without pre-existing ground control. |
| first_indexed | 2024-12-11T05:24:54Z |
| format | Article |
| id | doaj.art-ea4a64537d35431f92fd0d4ed2ab4c12 |
| institution | Directory Open Access Journal |
| issn | 2296-7745 |
| language | English |
| last_indexed | 2024-12-11T05:24:54Z |
| publishDate | 2020-06-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Marine Science |
| spelling | doaj.art-ea4a64537d35431f92fd0d4ed2ab4c122022-12-22T01:19:36ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452020-06-01710.3389/fmars.2020.00525541617Accurate Bathymetric Maps From Underwater Digital Imagery Without Ground ControlGerald A. Hatcher0Jonathan A. Warrick1Andrew C. Ritchie2Evan T. Dailey3David G. Zawada4Christine Kranenburg5Kimberly K. Yates6Pacific Coastal and Marine Science Center, United States Geological Survey, Santa Cruz, CA, United StatesPacific Coastal and Marine Science Center, United States Geological Survey, Santa Cruz, CA, United StatesPacific Coastal and Marine Science Center, United States Geological Survey, Santa Cruz, CA, United StatesPacific Coastal and Marine Science Center, United States Geological Survey, Santa Cruz, CA, United StatesSt. Petersburg Coastal and Marine Science Center, United States Geological Survey, St. Petersburg, FL, United StatesSt. Petersburg Coastal and Marine Science Center, United States Geological Survey, St. Petersburg, FL, United StatesSt. Petersburg Coastal and Marine Science Center, United States Geological Survey, St. Petersburg, FL, United StatesStructure-from-Motion (SfM) photogrammetry can be used with digital underwater photographs to generate high-resolution bathymetry and orthomosaics with millimeter-to-centimeter scale resolution at relatively low cost. Although these products are useful for assessing species diversity and health, they have additional utility for quantifying benthic community structure, such as coral growth and fine-scale elevation change over time, if accurate length scales and georeferencing are included. This georeferencing is commonly provided with “ground control,” such as pre-installed seafloor benchmarks or identifiable “static” features, which can be difficult and time consuming to install, survey, and maintain. To address these challenges, we developed the SfM Quantitative Underwater Imaging Device with Five Cameras (SQUID-5), a towed surface vehicle with an onboard survey-grade Global Navigation Satellite System (GNSS) and five rigidly mounted downward-looking cameras with overlapping views of the seafloor. The cameras are tightly synchronized with both the GNSS and each other to collect quintet photo sets and record the precise location of every collection event. The system was field tested in July 2019 in the U.S. Florida Keys, in water depths ranging from 3 to 9 m over a variety of bottom types. Surveying accuracy was assessed using pre-installed stations with known coordinates, machined scale bars, and two independent surveys of a site to evaluate repeatability. Under a range of sea conditions, ambient lighting, and water clarity, we were able to map living and senile coral reef habitats and sand waves at mm-scale resolution. Data were processed using best practice SfM techniques without ground control and local measurement errors of horizontal and vertical scales were consistently sub-millimeter, equivalent to 0.013% RMSE relative to water depth. Survey-to-survey repeatability RMSE was on the order of 3 cm without georeferencing but could be improved to several millimeters with the incorporation of one or more non-surveyed marker points. We demonstrate that the SQUID-5 platform can map complex coral reef and other seafloor habitats and measure mm-to-cm scale changes in the morphology and location of seafloor features over time without pre-existing ground control.https://www.frontiersin.org/article/10.3389/fmars.2020.00525/fullunderwater photogrammetryStructure-from-Motionsynchronized camerascoral reefdigital surface modelorthomosaic |
| spellingShingle | Gerald A. Hatcher Jonathan A. Warrick Andrew C. Ritchie Evan T. Dailey David G. Zawada Christine Kranenburg Kimberly K. Yates Accurate Bathymetric Maps From Underwater Digital Imagery Without Ground Control Frontiers in Marine Science underwater photogrammetry Structure-from-Motion synchronized cameras coral reef digital surface model orthomosaic |
| title | Accurate Bathymetric Maps From Underwater Digital Imagery Without Ground Control |
| title_full | Accurate Bathymetric Maps From Underwater Digital Imagery Without Ground Control |
| title_fullStr | Accurate Bathymetric Maps From Underwater Digital Imagery Without Ground Control |
| title_full_unstemmed | Accurate Bathymetric Maps From Underwater Digital Imagery Without Ground Control |
| title_short | Accurate Bathymetric Maps From Underwater Digital Imagery Without Ground Control |
| title_sort | accurate bathymetric maps from underwater digital imagery without ground control |
| topic | underwater photogrammetry Structure-from-Motion synchronized cameras coral reef digital surface model orthomosaic |
| url | https://www.frontiersin.org/article/10.3389/fmars.2020.00525/full |
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