Project Planning:
Project Goals and Data Resolution
When planning a benthic habitat mapping project, it is important to
consider the image resolution needed to achieve the specific goals of
the project. While it is generally desirable to collect the highest
resolution data possible to create detailed and accurate maps, factors
such as money, time, resources, and physical constraints must be taken
into account. An appropriate balance between regional and localized
methods must be achieved based on these factors.
 |
Comparison between a Landsat Thematic Mapper image (30 meter resolution) and
a digital orthophoto (1 meter resolution).
Courtesy: NOAA Coastal Services Center |
The selection of tools and techniques may be determined by the level
of habitat discrimination required. If coarse habitat mapping is all
that is needed, then lower resolution data from satellite
imagery may be a good option. If detailed habitat mapping is required,
then techniques that yield higher resolution (such as aerial
photography) may be required.
The various types of echosounders are quite similar in their resolution,
but differ in the amount of coverage they provide. For example, depth
soundings from single-beam surveys generally cover only 5-10% of the
desired area. Therefore, mapping of single-beam data requires a large
amount of interpolation between data points. On the other hand, multibeam surveys,
while more expensive, provide greater seafloor coverage. Multibeam systems
are well suited for mapping large areas of the seafloor with a complex
mix of habitat types. In flat or gradually sloping areas, single-beam
bathymetry combined with side-scan
sonar data may be sufficient.
 |
Color, hill-shaded model views of a single-beam
bathymetry dataset and a multibeam bathymetry dataset.
Courtesy: Science Applications International Corporation |
Fine-scale techniques provide spatial resolution on a scale from millimeters
to centimeters. Sediment grabs
and cores are useful for sampling the sub-bottom biological community
and sediment composition. They provide discrete data with relatively
low coverage of the seafloor. Sediment profile
imaging also produces point data with low coverage. Its usefulness
lies in its ability to provide a high resolution optical image of the
surface sediment, including the sediment-water interface, regardless
of water clarity. Biological and geophysical features can be discerned
using this technique.
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