Geographical Survey Institute
Geographical Survey Institute
Houlie N.,University of California at Berkeley |
Occhipinti G.,CNRS Paris Institute of Global Physics |
Blanchard T.,University of Leeds |
Shapiro N.,CNRS Paris Institute of Global Physics |
And 2 more authors.
Scientific Reports | Year: 2011
Recently, co-seismic seismic source characterization based on GPS measurements has been completed in near-and far-field with remarkable results. However, the accuracy of the ground displacement measurement inferred from GPS phase residuals is still depending of the distribution of satellites in the sky. We test here a method, based on the double difference (DD) computations of Line of Sight (LOS), that allows detecting 3D co-seismic ground shaking. The DD method is a quasi-analytically free of most of intrinsic errors affecting GPS measurements. The seismic waves presented in this study produced DD amplitudes 4 and 7 times stronger than the background noise. The method is benchmarked using the GEONET GPS stations recording the Hokkaido Earthquake (2003 September 25th, Mw = 8.3).
Sobue S.-I.,Japan Aerospace Exploration Agency |
Araki H.,National Astronomical Observation of Japan |
Tazawa S.,National Astronomical Observation of Japan |
Noda H.,National Astronomical Observation of Japan |
And 3 more authors.
Advanced Techniques in Computing Sciences and Software Engineering | Year: 2010
This paper describes an application of a geographical information system with visualized and sonification lunar remote sensing data provided by Japan's lunar explorer (SELENE "KAGUYA"). Web based GIS is a very powerful tool which lunar scientists can use to visualize and access remote sensing data with other geospatial information. We discuss enhancement of the pseudo-colored visual map presentation of lunar topographical altimetry data derived from LALT and the map of the data to several sound parameters (Interval, harmony, and tempo). This paper describes an overview of this GIS with a sonification system, called "Moonbell". © Springer Science+Business Media B.V. 2010.
Tateishi R.,Chiba University |
Uriyangqai B.,Inner Mongolia Normal University |
Al-Bilbisi H.,University of Jordan |
Ghar M.A.,National Authority for Remote Sensing and Space science NARSS |
And 9 more authors.
International Journal of Digital Earth | Year: 2011
Global land cover is one of the fundamental contents of Digital Earth. The Global Mapping project coordinated by the International Steering Committee for Global Mapping has produced a 1-km global land cover dataset - Global Land Cover by National Mapping Organizations. It has 20 land cover classes defined using the Land Cover Classification System. Of them, 14 classes were derived using supervised classification. The remaining six were classified independently: urban, tree open, mangrove, wetland, snow/ice, andwater. Primary source data of this land cover mapping were eight periods of 16-day composite 7-band 1-km MODIS data of 2003. Training data for supervised classification were collected using Landsat images, MODIS NDVI seasonal change patterns, Google Earth, Virtual Earth, existing regional maps, and expert's comments. The overall accuracy is 76.5% and the overall accuracy with the weight of the mapped area coverage is 81.2%. The data are available from the Global Mapping project website (http://www.iscgm.org/). TheMODISdata used, land cover training data, and a list of existing regional maps are also available from the CEReS website. This mapping attempt demonstrates that training/validation data accumulation from different mapping projects must be promoted to support future global land cover mapping. © 2011 Taylor & Francis.
Panet I.,CNRS Paris Institute of Global Physics |
Kuroishi Y.,Geographical Survey Institute |
Holschneider M.,University of Potsdam
International Association of Geodesy Symposia | Year: 2012
For geodetic and geophysical purposes, such as geoid determination or the study of the Earth's structure, heterogeneous gravity datasets of various origins need to be combined over an area of interest, in order to derive a local gravity model at the highest possible resolution. The quality of the obtained gravity model strongly depends on the use of appropriate noise models for the different datasets in the combination process. In addition to random errors, those datasets are indeed often affected by systematic biases and correlated errors. Here we show how wavelets can be used to realize such combination in a flexible and economic way, and how the use of domain decomposition approaches allows to recalibrate the noise models in different wavebands and for different areas. We represent the gravity potential as a linear combination of Poisson multipole wavelets (Holschneider et al. 2003). We compute the wavelet model of the gravity field by regularized least-squares adjustment of the datasets. To solve the normal system, we apply the Schwarz iterative algorithms, based on a domain decomposition of the models space. Hierarchical scale subdomains are defined as subsets of wavelets at different scales, and for each scale, block subdomains are defined based on spatial splittings of the area. In the computation process, the data weights can be refined for each subdomain, allowing to take into account the effect of correlated noises in a simple way. Similarly, the weight of the regularization can be recalibrated for each subdomain, introducing non-stationarity in the a priori assumption of smoothness of the gravity field. We show and discuss examples of application of this method for regional gravity field modelling over a test area in Japan. © Springer-Verlag Berlin Heidelberg 2012.
Munekane H.,Geographical Survey Institute |
Boehm J.,Vienna University of Technology
Journal of Geodesy | Year: 2010
Troposphere-induced errors in GPS-derived geodetic time series, namely, height and zenith total delays (ZTDs), over Japan are quantitatively evaluated through the analyses of simulated GPS data using realistic cumulative tropospheric delays and observed GPS data. The numerical simulations show that the use of a priori zenith hydrostatic delays (ZHDs) derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather model data and gridded Vienna mapping function 1 (gridded VMF1) results in smaller spurious annual height errors and height repeatabilities (0.45 and 2.55 mm on average, respectively) as compared to those derived from the global pressure and temperature (GPT) model and global mapping function (GMF) (1.08 and 3.22 mm on average, respectively). On the other hand, the use of a priori ZHDs derived from the GPT and GMF would be sufficient for applications involving ZTDs, given the current discrepancies between GPS-derived ZTDs and those derived from numerical weather models. The numerical simulations reveal that the use of mapping functions constructed with fine-scale numerical weather models will potentially improve height repeatabilities as compared to the gridded VMF1 (2.09 mm against 2.55 mm on average). However, they do not presently outperform the gridded VMF1 with the observed GPS data (6.52 mm against 6.50 mm on average). Finally, the commonly observed colored components in GPS-derived height time series are not primarily the result of troposphere-induced errors, since they become white in numerical simulations with the proper choice of a priori ZHDs and mapping functions. © 2010 Springer-Verlag.
Haas R.,Chalmers University of Technology |
Sekido M.,Japan National Institute of Information and Communications Technology |
Hobiger T.,Japan National Institute of Information and Communications Technology |
Kondo T.,Japan National Institute of Information and Communications Technology |
And 6 more authors.
Artificial Satellites | Year: 2010
We give a short overview about the achievements of the Fennoscandian- Japanese ultra-rapid dUT1-project that was initiated in early 2007. The combination of real-time data transfer, near real-time data conversion and correlation, together with near-real time data analysis allows to determine dUT1 with a very low latency of less than 5 minutes after the end of a VLBI-session. The accuracy of these ultra-rapid dUT1-results is on the same order than the results of the standard rapid-service of the International Earth Rotation and Reference Frame Service (IERS). The ultra-rapid approach is currently extended to 24 hour sessions and is expected to become an important contribution for the future next generation VLBI system called VLBI2010.
Heggy E.,Jet Propulsion Laboratory |
Sedze M.,CNRS Paris Institute of Global Physics |
Sedze M.,Institute Geographique National |
Bretar F.,Institute Geographique National |
And 4 more authors.
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2010
Until recently the coarse resolution of topographic mapping acted as a break on understanding the forces and processes that shape the Earth's surface. However, active surface deformation is an important indicator for the earth crustal dynamics since it is directly linked to earthquakes, volcanic eruptions and landslides. Both airborne laser scanning systems (LiDAR) and spaceborne interferometric synthetic aperture radars (InSAR) have provided valuable information for many case studies requiring high-resolution characterization of ground movement in relatively large areas to assess the threat and impact of natural hazards especially for volcanic eruptions. © 2010 IEEE.
Iwahashi J.,Geographical Survey Institute |
Kamiya I.,Geographical Survey Institute |
Matsuoka M.,Japan National Institute of Advanced Industrial Science and Technology
Geomorphology | Year: 2010
The average shear wave velocity for the top 30 m (Vs30) is one of the simple predictors of earthquake ground motion amplification. We performed a multiple linear regression analysis of the logarithm of observed Vs30 at 1646 locations in Japan with three topographic attributes (slope gradient, surface texture, and the logarithm of elevation) calculated from a 50-m DEM. A Vs30 map was created using the partial regression coefficients. The determination coefficient was 0.318. The development of the estimation method of Vs30 from a DEM will be useful for earthquake vulnerability assessment. © 2009 Elsevier B.V. All rights reserved.