• Journal of Power System Engineering
• /
• v.13 no.2
• /
• pp.63-70
• /
• 2009

This paper discusses the influence on long-tenn predictions of the ship response in ocean by using the Global Wave Statistics data, GWS, and wave information from the remote sensing satellites. GWS's standard scatter diagrams of significant wave height and zero-crossing wave period are suggested to be corrected to a round number of 0.01/1000 fitted with a statistical analytic model of the conditional lognormal distribution for zero-crossing wave period. The GEOSAT satellite data are utilized which presented by I. R. Young and G. J. Holland (1996, named as GEOSAT data). At first, qualities of this data are investigated, and statistical characteristic trends are studied by means of applying known probability distribution functions. The wave height data of GEOSAT are compared to the data observed onboard merchant ships, the data observed by measure instrument installed on the ocean-going container ship and so on. To execute a long-tenn prediction of ship response, joint probability functions between wave height and wave period are introduced, therefore long-term statistical predictions are executed by using the functions.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.12 no.1
• /
• pp.107-118
• /
• 1994

As satellite altimetry is being progressed to apply with heigher precision to maginal seas, it was necessary to improve correction procedures for tidal signals in altimetry with more accurate tidal model than well-known model of Schwiderski for studying marginal sea dynamics. As a first step, tidal regime of semidiurnal tides$(M_2,\;S_2,\;N_2,\;K_2)$ and diurnal tides$(K_1,\;O_1,\;P_1,\;Q_1)$ were computed with a finer details of formulation of tidal model over the East Asian Marginal Seas covering the Okhotsk Sea and South China Sea and part of Northwest Pacific Ocean with mesh resolutions of 1/6$^{\circ}$. Subsequently the computed sets of harmonic constants from the model were used to remove the tide in selected Sea Surface Heights from Geosat in the modelled region. Preliminary correction procedure suggested in the present study may be extensively used for obtaining Sea Surface Topography over the East Asian Marginal Seas, especially for the region where Schwiderski's harmonic constants are not available.

• 한국해양학회지
• /
• v.29 no.4
• /
• pp.383-391
• /
• 1994

Sea surface height geoidal undulation, and gravity anomaly derived from satellite altimeter measurements are described. Assuming mean sea surface height (MSSH) as geoidal undulation, MSSH was converted to gravity anomaly. the result shows that the gravity anomaly derived from satellite altimeter data can be mapped to an accuracy of the surface ship gravity measurements. The data used for the conversion is the two-year mean sea surface height obtained from GEOSAT Exact Repeat Mission. The conversion was carried out using fast Fourier transform with plane approximation. In this process, the so called remove-restore method was employed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.13 no.1
• /
• pp.61-68
• /
• 1995

This paper is to provide a reference surface geoid for geodetic applications of satellite altimeter data. The paticular satellite alone or the combination with other altimeter data could be used for the recovery of geoid un-dulations and gravity anomalies in the ocean areas. This paper also describes the geoidal undulation in the ocean area of Korean Peninusla using Geosat, ERS-1 and Topex/Poseidon data. The results show that the quasi-stationary sea surface topography (557) is estimated to be less than 10 cm RMS value in the ocean area of Korean Peninsula. This can be considered as an altimeter geoid.

• Proceedings of the KSEEG Conference
• /
• 2000.04b
• /
• pp.140-142
• /
• 2000

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 1996.10a
• /
• pp.10-13
• /
• 1996

Satellite-borne altimeters are one of the most important global ocean measurement and monitoring techniques available to modern oceanographers. While the U.S. Navy's GEOdetic SATellite (GEOSAT) mission in the mid-eighties firmly established its value, the full potential of satellite altimetry was not realized until the launch of the NASA/CNES TOPEX/Poseidon precision altimeter in 1992. (omitted)

• Proceedings of the KSRS Conference
• /
• 2002.10a
• /
• pp.337-340
• /
• 2002

Monitoring of wave height is important primarily to reduce storm risks at sea and along the coast. Wave heights in recent years have increased 50% for the last 40 years, thus requiring intensive monitoring. Satellite altimetry offers a powerful tool for regular and extensive monitoring of the wave height. We extracted significant wave height (SWH) using several altimeter missions from 1987-1995 over the Northwest Pacific and compared with ECMWF reanalysis (ERA) products. For large wave heights > 2.5 m, the ERA wave heights are smaller than the altimetric ones, while for small wave heights the ERA wave heights are larger. Comparison in SWH between altimetric derivations and ERA model products shows the discrepancy of 0.46-0.21$\times$SWH(m).

• Korean Journal of Remote Sensing
• /
• v.19 no.1
• /
• pp.31-36
• /
• 2003

We extracted significant wave height (SWH) using several altimeter missions from 1987-1995 over the Northwest Pacific ocean and compared with ECMWF (European Center for Medium- Range Forecast) reanalysis (ERA) products. For large wave heights the ERA wave heights are smaller than the altimetric ones, while for small wave heights the ERA wave heights are larger Comparison in SWH between altimetric derivations and ERA model products shows the discrepancy of 0.46-0.21$\times$SWH (m). Methods for propagating this differences into ERA wind error are presented.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.14 no.2
• /
• pp.127-139
• /
• 1996

This paper presents a procedure to recover sea surface heights (SSH) and free-air (FA) gravity anomalies from dense satellite altimeter SSH data with enhanced accuracies over the full spectrum of the gravity field. A wavenumber correlation filtering (WCF) of co-linear SSH tracks is developed for the coherent signals of sub-surface geological masses. Orbital cross-over adjustments with bias parameters are applied to the filtered SSH data, which are then separated into two groups of ascending and descending tracks and gridded with tensioned splines. A directional sensitive filter (DSF) is developed to reduce residual errors in the orbital adjustments that appear as track patterned SSH. Finally, FA gravity anomalies can be obtained by the application of a gradient filter on a high resolution estimate of geoid undulations after subtracting dynamic sea surface topography (DSST) from the SSH. These procedures are applied to the Geosat Geodetic Mission (GM) data of the southern oceans in a test area of ca. $900km\;\times{1,200}\;km$ to resolve geoid undulations and FA gravity anomalies to wavelengths of-10 km and larger. Comparisons with gravity data from ship surveys, predictions by least squares collocation (LSC), and 2 versions of NOAA's predictions using vertical deflections illustrate the performance of this procedure for recovering all elements of the gravity spectrum. Statistics on differences between precise ship data and predicted FA gravity anomalies show a mean of 0.1 mgal, an RMS of 3.5 mgal, maximum differences of 10. 2 mgal and -18.6 mgal, and a correlation coefficient of 0.993 over four straight ship tracks of ca. 1,600 km where gravity changes over 150 mgals.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.13 no.2
• /
• pp.177-185
• /
• 1995

Gravity anomalies were recovered on a $5'\times{5'}$grid using the sea surface height data obtained from the combination of Geosat, ERS-1, Topex/Poseidon altimeter data around Korean Peninsula bounded by latitude between $30^\circ{N}\;and\;50^\circ{N}$ and longitude $120^\circ{E}\;to\;140^\circ{E.}$ In order to recover the gravity anomalies from SSH(Sea Surface Height), inverse FFT technique was applied. The estimated gravity anomalies were compared with gravity anomalies measured by shipboard around Korean Peninsula. In comparison with the differences of gravity anomaly between measured data and altimeter data, the mean and the standard deviation were found to be -0.51 mGal and 13.48 mGal, respectively. In case of comparison between the measured data and the OSU91A geopotential model, the mean and the standard deviation were found to be 11.93 mGal and 19.19 mGal, respectively. The comparison of gravity anomalies obtained from the OSU91A geopotential model and the altimeter data was carried out. The results were mean of 5.30 meal and standard deviation of 19.62 mGal. From the results, we could be concluded that the gravity anomalies computed from the altimeter data is used to the geoid computation instead of the measured data.