30,221 research outputs found
Dynamics of Land Use and Land Cover Changes in Harare, Zimbabwe: A Case Study on the Linkage between Drivers and the Axis of Urban Expansion
With increasing population growth, the Harare Metropolitan Province has experienced accelerated land use and land cover (LULC) changes, influencing the city’s growth. This study aims to assess spatiotemporal urban LULC changes, the axis, and patterns of growth as well as drivers influencing urban growth over the past three decades in the Harare Metropolitan Province. The analysis was based on remotely sensed Landsat Thematic Mapper and Operational Land Imager data from 1984–2018, GIS application, and binary logistic regression. Supervised image classification using support vector machines was performed on Landsat 5 TM and Landsat 8 OLI data combined with the soil adjusted vegetation index, enhanced built-up and bareness index and modified difference water index. Statistical modelling was performed using binary logistic regression to identify the influence of the slope and the distance proximity characters as independent variables on urban growth. The overall mapping accuracy for all time periods was over 85%. Built-up areas extended from 279.5 km2 (1984) to 445 km2 (2018) with high-density residential areas growing dramatically from 51.2 km2 (1984) to 218.4 km2 (2018). The results suggest that urban growth was influenced mainly by the presence and density of road networks
Radio-Echo Sounding Over Polar Ice Masses
Peer reviewedPublisher PD
Evidence of Quaternary tectonics along RÃo Grande valley, southern Malargüe fold and thrust belt, Mendoza, Argentina
The Malargüe fold and thrust belt is developed in the Argentinian Andes between 34° and 37° S, through the tectonic inversion of Upper Triassic and Lower Jurassic depocenters of the Neuquén Basin, with an uplift history since the Cretaceous. Evidence of Quaternary deformation has been described in the northern part of it (34–34.5°S), potentially coeval to neotectonic activity along the eastern edge of San Rafael block. To the south, compressional and extensional structures active during the Quaternary were found in the Dorso de los Chihuidos along the Agrio fold and thrust belt front (37.5–38°S). Contrastingly, the southern segment of the Malargüe fold and thrust belt between these two areas with described neotectonic activity is partially covered by Quaternary products of the Payún Matrú volcanic field, that may hide evidence of recent deformation. In this 300 km gap of neotectonic information, the landscape imprint of two individual structures aligned in the mountain front through the RÃo Grande valley was analyzed. New evidence of neotectonic deformation were recognized, in particular over the western slope of the Cara Cura range, expressed by faulting and folding of Quaternary deposits and lava flows. An 40Ar/39Ar age from a deformed lava flow at the flanks of an anticline in the foothills of the Cara Cura range may suggest at least an upper Pleistocene compressional tectonic activity. Longitudinal river profile analysis revealed anomalies that show some correlation with the neotectonic structures described, especially knickpoints and concavity index changes. Meanwhile normalized steepness index values showed a moderate response to recent deformation. A proposed schematic geomorphic evolution for this segment of RÃo Grande river is discussed to put the neotectonic activity into the context of landscape formation. All together this evidence supports the idea of an active front through the RÃo Grande valley during the Quaternary, coetaneous to an active broken foreland to the east in the southern Central Andes.Fil: Colavitto, Bruno. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Sagripanti, LucÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Fennell, Lucas MartÃn. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Costa, Carlos. Universidad Nacional de San Luis. Facultad de Ciencias FÃsico Matemáticas y Naturales. Departamento de GeologÃa; Argentin
Remote sensing inputs to landscape models which predict future spatial land use patterns for hydrologic models
A tropical forest area of Northern Thailand provided a test case of the application of the approach in more natural surroundings. Remote sensing imagery subjected to proper computer analysis has been shown to be a very useful means of collecting spatial data for the science of hydrology. Remote sensing products provide direct input to hydrologic models and practical data bases for planning large and small-scale hydrologic developments. Combining the available remote sensing imagery together with available map information in the landscape model provides a basis for substantial improvements in these applications
Glacier dynamics near the calving front of Bowdoin Glacier, northwestern Greenland
To better understand recent rapid recession of marine-terminating glaciers in Greenland, we performed satellite and field observations near the calving front of Bowdoin Glacier, a 3 km wide outlet glacier in northwestern Greenland. Satellite data revealed a clear transition to a rapidly retreating phase in 2008 from a relatively stable glacier condition that lasted for >20 years. Ice radar measurements showed that the glacier front is grounded, but very close to the floating condition. These results, in combination with the results of ocean depth soundings, suggest bed geometry in front of the glacier is the primary control on the rate and pattern of recent rapid retreat. Presumably, glacier thinning due to atmospheric and/or ocean warming triggered the initial retreat. In situ measurements showed complex short-term ice speed variations, which were correlated with air temperature, precipitation and ocean tides. Ice speed quickly responded to temperature rise and a heavy rain event, indicating rapid drainage of surface water to the bed. Semi-diurnal speed peaks coincided with low tides, suggesting the major role of the hydrostatic pressure acting on the calving face in the force balance. These observations demonstrate that the dynamics of Bowdoin Glacier are sensitive to small perturbations occurring near the calving front
Deep learning in remote sensing: a review
Standing at the paradigm shift towards data-intensive science, machine
learning techniques are becoming increasingly important. In particular, as a
major breakthrough in the field, deep learning has proven as an extremely
powerful tool in many fields. Shall we embrace deep learning as the key to all?
Or, should we resist a 'black-box' solution? There are controversial opinions
in the remote sensing community. In this article, we analyze the challenges of
using deep learning for remote sensing data analysis, review the recent
advances, and provide resources to make deep learning in remote sensing
ridiculously simple to start with. More importantly, we advocate remote sensing
scientists to bring their expertise into deep learning, and use it as an
implicit general model to tackle unprecedented large-scale influential
challenges, such as climate change and urbanization.Comment: Accepted for publication IEEE Geoscience and Remote Sensing Magazin
Density Variations in the NW Star Stream of M31
The Pan Andromeda Archeological Survey (PAndAS) CFHT Megaprime survey of the
M31-M33 system has found a star stream which extends about 120 kpc NW from the
center of M31. The great length of the stream, and the likelihood that it does
not significantly intersect the disk of M31, means that it is unusually well
suited for a measurement of stream gaps and clumps along its length as a test
for the predicted thousands of dark matter sub-halos. The main result of this
paper is that the density of the stream varies between zero and about three
times the mean along its length on scales of 2 to 20 kpc. The probability that
the variations are random fluctuations in the star density is less than 10^-5.
As a control sample we search for density variations at precisely the same
location in stars with metallicity higher than the stream, [Fe/H]=[0, -0.5] and
find no variations above the expected shot noise. The lumpiness of the stream
is not compatible with a low mass star stream in a smooth galactic potential,
nor is it readily compatible with the disturbance caused by the visible M31
satellite galaxies. The stream's density variations appear to be consistent
with the effects of a large population of steep mass function dark matter
sub-halos, such as found in LCDM simulations, acting on an approximately 10Gyr
old star stream. The effects of a single set of halo substructure realizations
are shown for illustration, reserving a statistical comparison for another
study.Comment: ApJ revised version submitte
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