11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 17: Emerging Techniques in Remote Sensing and Geospatial Analysis
17.581
Sun Glint Correction For Hyperspectral Shallow Water Imagery
Tiit KUTSER* 1 , Ele VAHTMÄE 1
1 Estonian Marine Institute, University of Tartu, Tallinn, Estonia
Current sung glint removal procedures assume zero water leaving signal in near infrared
part of spectrum. This assumption is not true in waters less than about 2 m deep where
part of the water leaving signal is originated from the bottom. As a result the shallow
water pixels are overcorrected during glint removal procedure and the shapes of
reflectance spectra are distorted. This has serious implications on shallow water bottom
classification results, especially if spectral libraries of in situ measured or modeled
reflectance spectra are used in classification of remote sensing imagery. Reef tops,
shallow water lagoons and many coastal areas are in waters less that 2 m deep. Therefore,
it is important to preserve spectral signatures of these areas if sun glint removal is
necessary. We propose an alternative sun glint removal procedure where the amount of
glint in each pixel is estimated from the depth of oxygen absorption feature at 760 nm
relative to a baseline. The new method removes sung glint successfully and at the same
time preserves the shape and magnitude of shallow water reflectance spectra.
17.582
Mapping A Path Reef Area in Detail Using Small-Format Aerial Photographs (Sfaf)
And Handy Gps in North-Eastern Brazil
Ricardo AMARAL* 1,2 , Filipe LIMA 1 , Luiz GONÇALVES 3
1 Department of Geology, Universidade Federal do Rio Grande do Norte - UFRN, Natal,
Brazil, 2 Programa de Pós-Graduação em Geodinâmica e Geofísica - PPGG, UFRN,
Natal, Brazil, 3 Departamento de Engenharia da Computação, UFRN, Natal, Brazil
An area approximately 750 x 550m with small underwater bioconstructions, at Maracajau
path reef, was mapped in detail using SFAP. It was georreferenced with help of handy
GPS and vetorized in a GIS software to produce and organize spatial information.
Maracajau path reef occurs about 60km to the north of Natal city. It is approximately
3km wide, 9km long, 7km away from the coast line and is partially visible at spring low
tides. SFAP were taken during low spring tide, to capture the underwater features better
by using a 35mm camera at 300m to 1000m over the ground, from a small aircraft. The
photographs were processed and analyzed using image processing softwares. Field works
using GPS pointed out the contour of the bigger bioconstructed bodies that were
recognized in the photos afterwards. The images were georeferenced using as ground
control points the bioconstructed bodies identified as well as little vessels. The features
were vetorized using visual interpretation and it was stored in a GIS. As a result we can
quantify the features in the area which is composed by approximately 60% of
bioconstructed bodies and by carbonate sand botton. We identified 555 bodies that were
separated by size. About 9% of them have less than 100m2 in area; 34% is between 100
and 1000m2; about 20% is between 1000 and 10000m 2 and a much closer assemblage of
bodies at the oceanic side of the area were classified altogether as a unique feature with
approximately 48000m2. This accurate and low cost protocol to map underwater features
has been done and the results showed efficiency and effectiveness, meanwhile it must be
considered as a complementary method and must be done associated with others
techniques.
17.583
Life After Death: Pleistocene Reefs Of Sisal; Yucatan Shelf
Salvador ZARCO-PERELLÓ* 1 , Joaquín Rodrigo GARZA-PEREZ 2 , Nuno SIMOES 2 , Maite
MASCARO-MIQUELAJAUREGUI 2 , Xavier CHIAPPA-CARRARA 2
1 Ecology, National Autonomous University of Mexico, Mexico City, Mexico, 2 Ecology,
National Autonomous University of Mexico, Mérida, Mexico
The shelf reefs in the Campeche Bank might be playing an important role in the connectivity
between the Caribbean and the Gulf of Mexico ecosystems. However, information from these
reef systems is scarce. This study focuses on the Sisal, Madagascar and Serpiente reefs, in the
northwest portion of the Yucatan Peninsula. A bathymetric survey was carried with a GPSsounder
and geostatistical methods were used to generate a geomorphology 3-D model. These
models were used to select Madagascar reef to implement a case of study to define and quantify
major reefscapes and zonation patterns. Fifteen 200 m phototransects were collected along the
bathymetric gradient direction; photographs (0.8 sq.m) were taken every 5 meters. Percentage
of cover of Morph-Functional Gruops was determined with a systematic 13 point count method
and a classification analysis (using multivariate statistics) defined five reefscapes. Distribution
maps of biotic components were generated using kriging. Few hexacorals were recorded, but
the structural complexity of the reef evidences coral accretion in the past. The hard coral
community was more likely killed during the last ice-age, with the decrease in the sea-level,
after when the sea-level increased they started flourishing under different environmental
conditions, favoring algal and octocoral development but no reef building hexacorals settlement
and growth. This work is the first in this specific region, the basis for many future studies and a
necessary ingredient of a GIS for the Yucatan Shelf.
17.584
Satellite Imagery As A Predictor For Diversity And Abundance Of Reef Fish in Diego
Garcia (Chagos Archipelago)
Samuel PURKIS* 1 , Nick GRAHAM 2 , Bernhard RIEGL 1
1 National Coral Reef Institute, Nova Southeastern University, Dania Beach, FL, 2 School of
Marine Science & Technology, University of Newcastle, Newcastle-upon-Tyne, United
Kingdom
The diversity, abundance and distribution of reef fish are related to heterogeneity and physical
complexity of benthic habitat. However, the field effort required to evaluate these aspects of the
benthos in situ, at the scale of entire reefscapes, is greatly constrained by logistical and
resource limitations. With moderate ground-truthing, both substratum type and seabed
topography are amenable to monitoring using satellite data. Here, remote sensing imagery was
used to resolve the bathymetry and benthic character of a reef system in Diego Garcia (British
Indian Ocean Territory). Replicate fish counts were made at seven measurement stations across
the study area using visual census. Monte Carlo simulation revealed that species richness and
abundance of several guilds and size groupings of reef fish appraised in situ were correlated
with the satellite-derived seabed parameters over areas of seafloor as large as 5,030 m2. The
study suggests that satellite remote sensing is capable of predicting habitat complexity at a scale
relevant to fish. Furthermore, as larger size classes of fish were better predicted with the
satellite habitat complexity data, this technique could be used to predict fish stocks and identify
potential sites for marine protected areas where intensive field surveys are not practical.
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