Time filter

Source Type

Ramdani D.,National Coordinating Agency for Surveys and Mapping
31st Asian Conference on Remote Sensing 2010, ACRS 2010

The use of GPS is increase in the last past year in all aspect of live. The disadvantage of using GPS is the height information not the actual height. To convert it to actual height is needed geoid undulation. In 2008 Adolfientje Kasenda has provided the Gravity data using airborne gravimetric. The survey used the GPS kinematic positioning to determine the coordinate in the plane which use for the position of the gravity data. The position of the gravity data was calculated from these GPS kinematic positioning with used of Bernese 5.0 GPS software. The program that used to calculate the coordinate is CODSPP and GPSEST with use zero difference. In CODSPP it had a RMS from 0.000 to 8.096 in X component, from 0.000 to 9.589 in Y component and from 0.000 to 5.317 in Z component. And in GPSEST it had a RMS from -1.874 to 0.994 in X component, from -2.104 to 5.906 in Y component and from 0.049 to 5.464 in Z component. Seen from the value of RMS of the coordinate from both program - The result of both program can be used as the coordinate of the airborne gravity point. GPSEST gives more accurate than CODSPP. Source

Ambarwulan W.,University of Twente | Ambarwulan W.,National Coordinating Agency for Surveys and Mapping | Salama M.S.,University of Twente | Mannaerts C.M.,University of Twente | Verhoef W.,University of Twente

Specific inherent optical properties (SIOP) of the Berau coastal waters were derived from in situ measurements and inversion of an ocean color model. Field measurements of water-leaving reflectance, total suspended matter (TSM), and chlorophyll a (Chl a) concentrations were carried out during the 2007 dry season. The highest values for SIOP were found in the turbid waters, decreasing in value when moving toward offshore waters. The specific backscattering coefficient of TSM varied by an order of magnitude and ranged from 0.003 m2 g-1, for clear open ocean waters, to 0.020 m2 g-1, for turbid waters. On the other hand, the specific absorption coefficient of Chl a was relatively constant over the whole study area and ranged from 0.022 m2 mg-1, for the turbid shallow estuary waters, to 0.027 m2 mg-1, for deeper shelf edge ocean waters. The spectral slope of colored dissolved organic matter light absorption was also derived with values ranging from 0.015 to 0.011 nm-1. These original derived values of SIOP in the Berau estuary form a corner stone for future estimation of TSMand Chl a concentration from remote sensing data in tropical equatorial waters. © The Author(s) 2010. Source

Ambarwulan W.,University of Twente | Ambarwulan W.,National Coordinating Agency for Surveys and Mapping | Mannaerts C.M.,University of Twente | van der Woerd H.J.,University of Amsterdam | Salama M.S.,University of Twente
Geocarto International

This article investigates the performance of MERIS reduced resolution data to monitor water quality parameters in the Berau estuary waters, Indonesia. Total suspended matter (TSM), Chlorophyll-a (Chl-a) concentration and diffuse attenuation coefficient (K d) were derived from MERIS data using three different algorithms for coastal waters: standard global processor (MERIS L2), C2R and FUB. The outcomes were compared to in situ measurements collected in 2007. MERIS data processed with C2R gave the best retrieval of Chl-a, while MERIS L2 performed the best for TSM retrieval, but large deviations from in situ data were observed, pointing at inversion problems over these tropical waters for all standard processors. Nevertheless, MERIS can be of use for monitoring equatorial coastal waters like the Berau estuary and reef system. Applying a K d(490) local algorithm to the MERIS RR data over the study area showed a sufficient good correlation to the in situ measurements (R 2 1/4 0.77). © 2010 Taylor & Francis. Source

Prawirodirdjo L.,University of California at San Diego | McCaffrey R.,Rensselaer Polytechnic Institute | Chadwell C.D.,University of California at San Diego | Bock Y.,University of California at San Diego | Subarya C.,National Coordinating Agency for Surveys and Mapping
Journal of Geophysical Research: Solid Earth

We use survey mode and continuous GPS data from 1991 to 2007 to examine fault segmentation in the earthquake cycle at the Sumatra megathrust, site of the 26 December 2004 Mw 9.1 Sumatra-Andaman, the 28 March 2005 M w 8.7 Nias-Simeulue, and the 12 September 2007 Mw 8.4 Mentawai earthquakes. These data, including new observations from 2006 and 2007, allow us to observe the final few years of one earthquake cycle and the beginning of the next. Our analysis reveals that the megathrust is segmented, a characteristic that may persist through multiple earthquake cycles. The Nias-Simeulue earthquake ruptured approximately the same region that broke in 1861, a 300 km long segment abutting the Sumatra-Andaman rupture zone. Farther southeast, the Mentawai segment of the megathrust (0.5°S-5°S), which produced M > 8 earthquakes in 1797 and 1833, is fully locked in the interseismic period but is flanked by two freely slipping regions, the Batu Islands in the NW and Enggano in the SE. The 12 September 2007 Mentawai earthquake sequence ruptured only the southern one third of the 1833 rupture zone. We model postseismic deformation from the Sumatra-Andaman and Nias-Simeulue earthquakes and find that afterslip was concentrated updip and downdip, respectively, from the main shocks. Comparing the velocity fields before and after 2001, we find the subduction zone underneath the Batu Islands and Enggano, which, prior to the earthquakes, was partially to fully coupled, appears now to be slipping freely. Thus, while the segmentation of the subduction zone is preserved, interseismic coupling on the subduction fault may vary with time. Copyright 2010 by the American Geophysical Union. Source

Ambarwulan W.,University of Twente | Ambarwulan W.,National Coordinating Agency for Surveys and Mapping | Verhoef W.,University of Twente | Mannaerts C.M.,University of Twente | Salama M.S.,University of Twente
International Journal of Remote Sensing

This study presents the application of a semi-empirical approach, based on the Kubelka-Munk (K-M) model, to retrieve the total suspended matter (TSM) concentration of water bodies from ocean colour remote sensing. This approach is validated with in situ data sets compiled from the tropical waters of Berau estuary, Indonesia. Compared to a purely empirical approach, the K-M model provides better results in the retrieval of TSM concentration on both data sets (in situ and Medium Resolution Imaging Spectrometer (MERIS)). In this study, the K-M model was calibrated with in situ measurements of remote-sensing reflectance (R rs) and TSM concentration. Next, the inverse K-M model was successfully applied to images taken by the MERIS instrument by generating regional maps of TSM concentration. MERIS top-of-atmosphere radiances were atmospherically corrected using the Moderate Spectral Resolution Atmospheric Transmittance (MODTRAN) radiative transfer model. The best correlation between R rs measured in situ and R rs MERIS was found to be at a wavelength of 620 nm. The TSM concentrations retrieved using the K-M model showed a lower root mean square error (RMSE), a higher coefficient of determination and a smaller relative error than those retrieved by the purely empirical approach. © 2012 Copyright Taylor and Francis Group, LLC. Source

Discover hidden collaborations