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Abstract-Automatic land cover classification maps were developed from Airborne Hyperspectral Scanner (HyMAP) imagery acquired May 8, 2000 over Smith Island, VA, a barrier island in the Virginia Coast Reserve. Both unsupervised and supervised classification approaches were used to create these products to evaluate relative merits and to develop models that would be useful to natural resource managers at higher spatial resolution than has been available previously. Ground surveys made by us in late October and early December 2000 and again in May, August, and October 2001 and May 2002 provided ground truth data for 20 land cover types. Locations of pure land cover types recorded with global positioning system (GPS) data from these surveys were used to extract spectral end-members for training and testing supervised land cover classification models. Unsupervised exploratory models were also developed using spatial-spectral windows and projection pursuit (PP), a class of algorithms suitable for extracting multimodal views of the data. PP projections were clustered by ISODATA to produce an unsupervised classification. Supervised models, which relied on the GPS data, used only spectral inputs because for some categories in particular areas, labeled data consisted of isolated single-pixel waypoints. Both approaches to the classification problem produced consistent results for some categories such as Spartina alterniflora, although there were differences for other categories. Initial models for supervised classification based on 112 HyMAP spectra, labeled in ground surveys, obtained reasonably consistent results for many of the dominant categories, with a few exceptions. For an invasive plant species, Phragmites australis, a particular concern of natural resource managers, this approach initially had an excessively high false-alarm rate. Increasing the number of spectral training samples by an order of magnitude and making concomitant improvements to the georectification led to dramatic improvements in this and other categories. The unsupervised spatial-spectral approach also found a cluster closely associated with Phragmites patches near the thicket boundary, but this approach did not identify the exposed are compared against HyMAP image spectra at model-predicted pixels and at validated GPS waypoints.Index Terms-Barrier islands, hyperspectral, in situ spectrometry, invasive plant species, land cover classification, neural networks, principle component analysis, projection pursuit, supervised classification, unsupervised classification.

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Abstract. In situ observation and remote sensing imagery reveal the presence of longitudinal velocity convergences over bathymetric channels in tidal estuaries. We present the results of numerical experiments designed to investigate the cause of these convergences for channels possessing shallow shoal regions and a deeper central region. The equations of motion for a homogeneous fluid on a rotating Earth are solved using a fully spectral code in the across-estuary (i.e., the vertical or x-z) plane, while no alongestuary flow variations (in the y direction) are permitted. A Gaussian-shaped bottom bathymetry is chosen. In the along-channel (y) direction we impose a pressure gradient which is the sum of constant and fluctuating parts to simulate the steady and tidally oscillating parts of the estuarine flow. The details of the transient response can be complicated, but we observe that for most (-80%) of the tidal cycle there exists a crossestuary recirculation cell colocated with a localized along-channel jet. Both of these are situated over the bottom bathymetric groove; the circulation is always clockwise when facing down current. This feature results from the generation of stream-wise vorticity through the tilting of planetary vorticity by the vertical shear of the along-estuary flow. A surface convergence-divergence pair is associated with the flow. The maximum value of each is seen to occur on the edge of the bathymetric feature but may migrate toward or away from the center as long as the current continues in the same direction. When the tide reverses, the feature reappears on the opposite shoal, and the migration of the convergence and divergence extrema begins again. We also find that the responses are qualitatively similar for all bathymetric grooves, even asymmetrically situated ones, provided that the estuary width-to-depth ratio is of order 100 or larger, the Rossby numbers are of order unity, and the Ekman layer thickness-to-channel-depth ratio is greater than -0.65.

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