94,084 research outputs found

    Breaking new ground in mapping human settlements from space -The Global Urban Footprint-

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    Today 7.2 billion people inhabit the Earth and by 2050 this number will have risen to around nine billion, of which about 70 percent will be living in cities. Hence, it is essential to understand drivers, dynamics, and impacts of the human settlements development. A key component in this context is the availability of an up-to-date and spatially consistent map of the location and distribution of human settlements. It is here that the Global Urban Footprint (GUF) raster map can make a valuable contribution. The new global GUF binary settlement mask shows a so far unprecedented spatial resolution of 0.4 arcsec (12m\sim12 m) that provides - for the first time - a complete picture of the entirety of urban and rural settlements. The GUF has been derived by means of a fully automated processing framework - the Urban Footprint Processor (UFP) - that was used to analyze a global coverage of more than 180,000 TanDEM-X and TerraSAR-X radar images with 3m ground resolution collected in 2011-2012. Various quality assessment studies to determine the absolute GUF accuracy based on ground truth data on the one hand and the relative accuracies compared to established settlements maps on the other hand, clearly indicate the added value of the new global GUF layer, in particular with respect to the representation of rural settlement patterns. Generally, the GUF layer achieves an overall absolute accuracy of about 85\%, with observed minima around 65\% and maxima around 98 \%. The GUF will be provided open and free for any scientific use in the full resolution and for any non-profit (but also non-scientific) use in a generalized version of 2.8 arcsec (84m\sim84m). Therewith, the new GUF layer can be expected to break new ground with respect to the analysis of global urbanization and peri-urbanization patterns, population estimation or vulnerability assessment

    Faint InfraRed Extragalactic Survey: Data and Source Catalogue of the MS1054-03 field

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    We present deep near-infrared Js, H, and Ks band imaging of a field around MS1054-03, a massive cluster at z=0.83. The observations were carried out with ISAAC at the ESO VLT as part of the Faint InfraRed Extragalactic Survey (FIRES). The total integration time amounts to 25.9h in Js, 24.4h in H, and 26.5h in Ks, divided nearly equally between four pointings covering 5.5'x5.3'. The 3-sigma total limiting AB magnitudes for point sources from the shallowest to deepest pointing are Js=26.0-26.2, H=25.5-25.8, and Ks=25.3-25.7. The effective spatial resolution of the coadded images has FWHM=0.48", 0.46", and 0.52" in Js, H, and Ks. We complemented the ISAAC data with deep optical imaging using existing HST WFPC2 mosaics in the F606W and F814W filters and new U, B and V band data from VLT FORS1. We constructed a Ks-band limited multicolour source catalogue to Ks(total,AB)=25 (about 5-sigma for point sources). The catalogue contains 1858 objects, of which 1663 have eight-band photometry. We describe the observations, data reduction, source detection and photometric measurements method. We present the number counts, colour distributions, and photometric redshifts z_ph of the catalogue sources. We find that our counts at the faint end 22<Ks(AB)<25, with slope dlog(N)/dm=0.20, lie at the flatter end of published counts in other deep fields and are consistent with those we derived in the HDF-South, the other FIRES field. Spectroscopic redshifts z_sp are available for about 330 sources in the MS1054-03 field; comparison between the z_ph and z_sp shows very good agreement, with =0.078. The MS1054-03 field observations complement our HDF-South data set with nearly five times larger area at about 0.7 brighter magnitudes. [ABRIDGED]Comment: Accepted for publication in the Astronomical Journal. 32 pages, 14 b/w figures, 1 color figur

    FAME: Face Association through Model Evolution

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    We attack the problem of learning face models for public faces from weakly-labelled images collected from web through querying a name. The data is very noisy even after face detection, with several irrelevant faces corresponding to other people. We propose a novel method, Face Association through Model Evolution (FAME), that is able to prune the data in an iterative way, for the face models associated to a name to evolve. The idea is based on capturing discriminativeness and representativeness of each instance and eliminating the outliers. The final models are used to classify faces on novel datasets with possibly different characteristics. On benchmark datasets, our results are comparable to or better than state-of-the-art studies for the task of face identification.Comment: Draft version of the stud

    The Chandra Source Catalog

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    The Chandra Source Catalog (CSC) is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. The first release of the CSC includes information about 94,676 distinct X-ray sources detected in a subset of public ACIS imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents <~ 30''. The catalog (1) provides access to the best estimates of the X-ray source properties for detected sources, with good scientific fidelity, and directly supports scientific analysis using the individual source data; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; and (3) provides efficient access to calibrated observational data and ancillary data products for individual X-ray sources, so that users can perform detailed further analysis using existing tools. The catalog includes real X-ray sources detected with flux estimates that are at least 3 times their estimated 1 sigma uncertainties in at least one energy band, while maintaining the number of spurious sources at a level of <~ 1 false source per field for a 100 ks observation. For each detected source, the CSC provides commonly tabulated quantities, including source position, extent, multi-band fluxes, hardness ratios, and variability statistics, derived from the observations in which the source is detected. In addition to these traditional catalog elements, for each X-ray source the CSC includes an extensive set of file-based data products that can be manipulated interactively.Comment: To appear in The Astrophysical Journal Supplement Series, 53 pages, 27 figure

    Deep optical imaging of the field of PC1643+4631A&B, I: Spatial distributions and the counts of faint galaxies

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    We present deep optical images of the PC1643+4631 field obtained at the WHT. This field contains two quasars at redshifts z=3.79 & 3.83 and a cosmic microwave background (CMB) decrement detected with the Ryle Telescope. The images are in U,G,V,R and I filters, and are complete to 25th magnitude in R and G and to 25.5 in U. The isophotal galaxy counts are consistent with the results of Metcalde et al. (1996), Hogg et al. (1997), and others. We find an excess of robust high-redshift Ly-break galaxy candidates with 25.0<R<25.5 compared with the mean number found in the fields studied by Steidel et al. -we expect 7 but find 16 - but we do not find that the galaxies are concentrated in the direction of the CMB decrement. However, we are still not sure of the distance to the system causing the CMB decrement. We have also used our images to compare the commonly used object-finding algorithms of FOCAS and SExtractor: we find FOCAS the more efficient at detecting faint objects and the better at dealing with composite objects, whereas SExtractor's morphological classification is more reliable, especially for faint objects near the resolution limit. More generally, we have also compared the flux lost using isophotal apertures on a real image with that on a noise-only image: recovery of artificial galaxies from the noise-only image significantly overestimates the flux lost from the galaxies, and we find that the corrections made using this technique suffer a systematic error of some 0.4 magnitudes.Comment: 17 pages, 40 figures, submitted to MNRAS, 1 large figure avaliable at ftp://ftp.mrao.cam.ac.uk:/pub/PC1643/paper1.figure18.p
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