10,370 research outputs found
Fingerprint Identification - New Directions
In most of the algorithms that have been suggested in this report, the fingerprint image is reduced to a relatively short sequence of integers. This reduces the memory size required by the database. Each algorithm is intended to exploit specific properties and features of the fingerprint that vary from finger to finger, and that can be localized relatively fast using digital techniques, thus also reducing the computational time requirements to a minimum. In each case, the sensitivity of the algorithm to small variations in the image was also discussed, with the aim of reducing the False Rejection Rate, and of increasing the general robustness of the algorithm
Spatial reasoning to determine stream network from LANDSAT imagery
In LANDSAT imagery, spectral and spatial information can be used to detect the drainage network as well as the relative elevation model in mountainous terrain. To do this, mixed information of material reflectance in the original LANDSAT imagery must be separated. From the material reflectance information, big visible rivers can be detected. From the topographic modulation information, ridges and valleys can be detected and assigned relative elevations. A complete elevation model can be generated by interpolating values for nonridge and non-valley pixels. The small streams not detectable from material reflectance information can be located in the valleys with flow direction known from the elevation model. Finally, the flow directions of big visible rivers can be inferred by solving a consistent labeling problem based on a set of spatial reasoning constraints
Glacial dynamics in pre-Alpine narrow valleys during the Last Glacial Maximum inferred by lowland fluvial records (northeast Italy)
During the Last Glacial Maximum (LGM), most of the major glaciated basins of the European Southern
Alps had piedmont lobes with large outwash plains; only a few glaciers remained within the valley. Piedmont
glaciers have left well-preserved terminal moraines, which allow for investigations to be carried out and inferences
to be made regarding their evolution and chronology. Valley glaciers\u2019 remnants, on the contrary, are often
scantly preserved, and changes can only be detected through correlations with glaciofluvial deposits in downstream
alluvial basins. The Brenta glacial system\u2019s dynamics in the glacier\u2019s terminal tract have been inferred
through a wide range of sediment analysis techniques on an alluvial stratigraphic record of the Brenta megafan
(northeast Italy), and via the mapping of in-valley glacial/glaciofluvial remnants. Glaciers flowing across narrow
gorges could possibly be slowed/blocked by such morphology, and glacial/sediment fluxes may then be diverted
to lateral valleys. Moreover, narrow valleys may induce glaciers to bulge and form icefalls at their front, preventing
the formation of terminal moraines. The Brenta Glacier was probably slowed/blocked by the narrow
Valsugana Gorge downstream of Primolano and was effectively diverted eastwards across a wind gap (Canal La
Menor Valley), joining the Cismon/Piave glaciers near Rocca and ending 2 km downstream. The Cismon and
Piave catchments started to contribute to the Brenta system just after 27 ka cal BP until at least 19:5 ka cal BP.
After the glaciers collapsed, the Piave River once again flowed into its main valley, whilst the Cismon continued
to merge with the Brenta.
This investigation shows that glacial catchments may vary significantly over time during a single glaciation in
rugged Alpine terrains. Sand petrography and the chemical/mineralogical composition of sediments are powerful
proxies for tracing such variations, as they propagate through the glacial and glaciofluvial systems and can be
recognized in the alluvial stratigraphic record far downstream from the glacier front
Spatial modelling of wetness for the Antarctic Dry Valleys
This paper describes a method used to model relative wetness for part of the Antarctic Dry Valleys using Geographic Information Systems (GIS) and remote sensing. The model produces a relative index of liquid water availability using variables that influence the volume and distribution of water. Remote sensing using Moderate Resolution Imaging Spectroradiometer (MODIS) images collected over four years is used to calculate an average index of snow cover and this is combined with other water sources such as glaciers and lakes. This water source model is then used to weight a hydrological flow accumulation model that uses slope derived from Light Detection and Ranging (LIDAR) elevation data. The resulting wetness index is validated using three-dimensional visualization and a comparison with a high-resolution Advanced Land Observing Satellite image that shows drainage channels. This research demonstrates that it is possible to produce a wetness model of Antarctica using data that are becoming widely available
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