Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 2

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
Content available remote Registration of multitemporal landsat images: a local correlation approach
EN
The study of multitemporal dataset is a typical task of remote sensing analysis. The areas subjected to catastrophic events, such as earthquake, flooding, fire, can be empbasized by visual interpretation of images acquired on different periods. Seeing that the instant of a natural event is known, the acquisition and the subsequent interpretation of remotely sensed data can be focused on pre and post event image, calling master the first one, representing the normal situation, and slaves the post event images. Multiple techniques of enhancing can be used, like bands ratios, vegetation indexes comparison, principal components analysis and coherence calculation. Since these are essentially pixel-to-pixel image operations, a good registration between slaves (post-event images) and master (pre-event image) is the first result to achieve. The work presents a possible solution of registration problem in multitemporal data sets. The event studied is the earthquake occurred in the urban area surrounding the gulf of Izmit, in Marmara Sea (Turkey), August 17, 1999. Earthquake damage assessment by interpretation of remotely sensed data is carried out generally by visual recognition of differences in high-resolution images, and the main geometrical task is the georectification of datasets for mapping purpose. In this case, a very precise registration between image data sets is not essential to achieve significant results. While Landsat images have 30 meters of resolution, visual recognition of single, damaged buildings is not possible, but the study of multispectral bands can be helpful to find variation of suńace reflectance, caused by building collapse and presence of debris seattered on the roads. However, different position of satellite during acquisition (different view angles) and different sub-pixel features cause duplication/shifting of objects. This fault is particularly visible making color composites using the whole dataset. A local correlation filter can be used instead usual registration algorithms, trying to improve feature by feature matching and local coherence, which can be helpful to interpret variation on reflectance due to damage.
EN
... THE TREATMENT OF TIME SERIE S DATA OF GPS PERMANENT STATIONS FOR EXTRACTING GEODETIC SIGNALS F.Vespe(l), P. Rutigliano(2) , R. Pacione(2) (I) Agenzia Spaziale !taliana , Centro di Geodesia Spaziale "G. Colombo". 75100 - Matera, Italy (2'relespazio S.pA Centro di Geodesia Spaziale "G. Colombo" - 75100 Matera, Italy Abstract It is wen known that the coordinates and the zenith total delays, estimated by the GPS, provide a big amount of information. Currentły a lot of stations with a very long data time series are present all over the world which malee now feasible to perform a critical analysis of the coordinates helpful for the detection of signals, such as: height displacements, velocities and strain rate suitable for geophysical interpretations. In the present work a method to assess the reliability of the time series is described and applied to some stations with a period of observations long 5 years at least. The method essentially build a "fingerprint" which give information how long time a signal can emerge ITom the time series. Furthermore with the method, harmonic signatures and jumps on the time series are detected and analysed. The method does not only detects the value of the jumps but also where they are placed along the time series. The good efficiency in the detection and evaluation of jumps is of utmost importance because they introduce spurious signatures which could dramatically delay the enhancement of the signals. So our method allows to detect jumps that could be neglected or not assessed or be themselves a signal to detect.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.