Mapping coral reef benthos, substrates, and bathymetry, using compact airborne Spectrographic Imager (CASI) data

Ian Leiper, Stuart Phinn, Chris Roelfsema, Karen Joyce, Arnold Dekker

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    Abstract

    This study used a reef-up approach to map coral reef benthos, substrates and bathymetry, with high spatial resolution hyperspectral image data. It investigated a physics-based inversion method for mapping coral reef benthos and substrates using readily available software: Hydrolight and ENVI. Compact Airborne Spectrographic Imager (CASI) data were acquired over Heron Reef in July 2002. The spectral reflectance of coral reef benthos and substrate types were measured in-situ, and using the HydroLight 4.2 radiative transfer model a spectral reflectance library of subsurface reflectance was simulated using water column depths from 0.5-10.0 m at 0.5 m intervals. Using the Spectral Angle Mapper algorithm, sediment, benthic micro-algae, algal turf, crustose coralline algae, macro-algae, and live coral were mapped with an overall accuracy of 65% to a depth of around 8.0 m; in waters deeper than 8.0 m the match between the classified image and field validation data was poor. Qualitative validation of the maps showed accurate mapping of areas dominated by sediment, benthic micro-algae, algal turf, live coral, and macro-algae. A bathymetric map was produced for water column depths 0.5-10.0 m, at 0.5 m intervals, and showed high correspondence with in-situ sonar data (R2 value of 0.93).
    Original languageEnglish
    Pages (from-to)6423-6445
    Number of pages23
    JournalRemote Sensing
    Volume6
    Issue number7
    DOIs
    Publication statusPublished - 14 Jul 2014

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    Compact Airborne Spectrographic Imager
    bathymetry
    coral reef
    benthos
    substrate
    macroalga
    microalga
    spectral reflectance
    coral
    reef
    water column
    coralline alga
    sonar
    sediment
    radiative transfer
    reflectance
    spatial resolution
    physics
    deep water
    software

    Cite this

    Leiper, Ian ; Phinn, Stuart ; Roelfsema, Chris ; Joyce, Karen ; Dekker, Arnold. / Mapping coral reef benthos, substrates, and bathymetry, using compact airborne Spectrographic Imager (CASI) data. In: Remote Sensing. 2014 ; Vol. 6, No. 7. pp. 6423-6445.
    @article{1ef369ea09e94fc7bc110ecf498b4d25,
    title = "Mapping coral reef benthos, substrates, and bathymetry, using compact airborne Spectrographic Imager (CASI) data",
    abstract = "This study used a reef-up approach to map coral reef benthos, substrates and bathymetry, with high spatial resolution hyperspectral image data. It investigated a physics-based inversion method for mapping coral reef benthos and substrates using readily available software: Hydrolight and ENVI. Compact Airborne Spectrographic Imager (CASI) data were acquired over Heron Reef in July 2002. The spectral reflectance of coral reef benthos and substrate types were measured in-situ, and using the HydroLight 4.2 radiative transfer model a spectral reflectance library of subsurface reflectance was simulated using water column depths from 0.5-10.0 m at 0.5 m intervals. Using the Spectral Angle Mapper algorithm, sediment, benthic micro-algae, algal turf, crustose coralline algae, macro-algae, and live coral were mapped with an overall accuracy of 65{\%} to a depth of around 8.0 m; in waters deeper than 8.0 m the match between the classified image and field validation data was poor. Qualitative validation of the maps showed accurate mapping of areas dominated by sediment, benthic micro-algae, algal turf, live coral, and macro-algae. A bathymetric map was produced for water column depths 0.5-10.0 m, at 0.5 m intervals, and showed high correspondence with in-situ sonar data (R2 value of 0.93).",
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    author = "Ian Leiper and Stuart Phinn and Chris Roelfsema and Karen Joyce and Arnold Dekker",
    year = "2014",
    month = "7",
    day = "14",
    doi = "10.3390/rs6076423",
    language = "English",
    volume = "6",
    pages = "6423--6445",
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    Mapping coral reef benthos, substrates, and bathymetry, using compact airborne Spectrographic Imager (CASI) data. / Leiper, Ian; Phinn, Stuart; Roelfsema, Chris; Joyce, Karen; Dekker, Arnold.

    In: Remote Sensing, Vol. 6, No. 7, 14.07.2014, p. 6423-6445.

    Research output: Contribution to journalArticleResearchpeer-review

    TY - JOUR

    T1 - Mapping coral reef benthos, substrates, and bathymetry, using compact airborne Spectrographic Imager (CASI) data

    AU - Leiper, Ian

    AU - Phinn, Stuart

    AU - Roelfsema, Chris

    AU - Joyce, Karen

    AU - Dekker, Arnold

    PY - 2014/7/14

    Y1 - 2014/7/14

    N2 - This study used a reef-up approach to map coral reef benthos, substrates and bathymetry, with high spatial resolution hyperspectral image data. It investigated a physics-based inversion method for mapping coral reef benthos and substrates using readily available software: Hydrolight and ENVI. Compact Airborne Spectrographic Imager (CASI) data were acquired over Heron Reef in July 2002. The spectral reflectance of coral reef benthos and substrate types were measured in-situ, and using the HydroLight 4.2 radiative transfer model a spectral reflectance library of subsurface reflectance was simulated using water column depths from 0.5-10.0 m at 0.5 m intervals. Using the Spectral Angle Mapper algorithm, sediment, benthic micro-algae, algal turf, crustose coralline algae, macro-algae, and live coral were mapped with an overall accuracy of 65% to a depth of around 8.0 m; in waters deeper than 8.0 m the match between the classified image and field validation data was poor. Qualitative validation of the maps showed accurate mapping of areas dominated by sediment, benthic micro-algae, algal turf, live coral, and macro-algae. A bathymetric map was produced for water column depths 0.5-10.0 m, at 0.5 m intervals, and showed high correspondence with in-situ sonar data (R2 value of 0.93).

    AB - This study used a reef-up approach to map coral reef benthos, substrates and bathymetry, with high spatial resolution hyperspectral image data. It investigated a physics-based inversion method for mapping coral reef benthos and substrates using readily available software: Hydrolight and ENVI. Compact Airborne Spectrographic Imager (CASI) data were acquired over Heron Reef in July 2002. The spectral reflectance of coral reef benthos and substrate types were measured in-situ, and using the HydroLight 4.2 radiative transfer model a spectral reflectance library of subsurface reflectance was simulated using water column depths from 0.5-10.0 m at 0.5 m intervals. Using the Spectral Angle Mapper algorithm, sediment, benthic micro-algae, algal turf, crustose coralline algae, macro-algae, and live coral were mapped with an overall accuracy of 65% to a depth of around 8.0 m; in waters deeper than 8.0 m the match between the classified image and field validation data was poor. Qualitative validation of the maps showed accurate mapping of areas dominated by sediment, benthic micro-algae, algal turf, live coral, and macro-algae. A bathymetric map was produced for water column depths 0.5-10.0 m, at 0.5 m intervals, and showed high correspondence with in-situ sonar data (R2 value of 0.93).

    KW - Algae

    KW - Bathymetry

    KW - Image matching

    KW - Mapping

    KW - Maps

    KW - Reefs

    KW - Reflection

    KW - Remote sensing

    KW - Spectroscopy

    KW - Radiative transfer

    KW - CASI

    KW - Compact airborne spectrographic imager

    KW - Coral reef

    KW - Crustose coralline algae

    KW - HyperSpectral

    KW - Hyperspectral image datas

    KW - Spectral angle mappers

    KW - Spectral reflectance libraries

    KW - Substrates

    U2 - 10.3390/rs6076423

    DO - 10.3390/rs6076423

    M3 - Article

    VL - 6

    SP - 6423

    EP - 6445

    JO - Remote Sensing

    JF - Remote Sensing

    SN - 2072-4292

    IS - 7

    ER -