(KAIKO-NANKAI, ODP) Izu-Ogasawara, Shikoku Basin and Kashima Oki

航海番号: KH-89-1 ; 航海日程: June 20 - July 13, 198

Evaluation of the geoid based on the SEASAT altimetry data at sea around Antarctica

The SEASAT radar altimetry data, which were obtained during its operational period from June to September 1978,have been processed, and the sea surface topography and/or the geoid in the area between 45°S and the margin of the Antarctic Continent have been contour-mapped. Mainly because of the uncertainty involved in the satellite altitude the sea surface topography includes maximum errors of ±5m. However, some significant features such as geoid depressions at the Ross Sea and the Weddell Sea or the regional geoid upheavals over the Indian Ocean off East Antarctica have been clearly displayed

Marine Gravimetry in Relation to the Antarctic Region

Recent techniques of marine gravimetry and gravimeters available are reviewed and some requirements for gravity measurements in the Antarctic region are mentioned in the first part. In the second part the gravity data so far obtained in the Antarctic region including both surface ship and satellite data are shown, and gravity anomalies there are discussed

(WESTPAC and IGBP) Tokyo-Guam-Cebu-Tokyo Geophysical and geological investigations of the Mariana region and Ayu trough

航海番号: KH-92-1 ; 航海日程: January 21 - March 4, 199

Sea gravimeter system of the icebreaker `SHIRASE\u27

The gravimeter system of the SHIRASE is the NIPRORI-1 sea gravimeter which was transferred from the icebreaker FUJI. In installing this gravimeter on the SHIRASE some changes for adaptation as well as some improvements for enhancing the capabilities were made. The main differences of the gravimeter installed on the SHIRASE are as follows : 1) The gravity sensor unit and the data processing unit were installed in separate rooms. 2) An air-cushioned board was placed in the gravity sensor room in order to reduce vibration of the floor caused by the engines. 3) The data processing unit was expanded, and computers and floppy disks were doubled. 4) Temperature regulation of the gravimeter was improved, so that it became possible to detect the tidal variation of gravity by the use of the existent gravity sensor. 5) Software for data processing was improved in two points; one concerned with the operation by interrogation and the other with the refinement of noise filtering

Surface configuration of the Antarctic ice sheet in the sector 30゜E - 80゜E using SEASAT altimetry data

Using Interim Geophysical Data Record (IGDR) of SEASAT radar altimetry, a configuration map of the Antarctic ice sheet in the area bounded by 30°and 80°E and latitude 72°S is compiled. A total of 7480 footprint data of every second sampling (6.62km apart) along 63 subsatellite groundtracks are obtained in the area. The area was divided into rectangles with side lengths of 0.1°in latitude and 0.4°in longitude, and the average elevation above sea level by SEASAT altimetry data within the rectangle is used for computer-aided contouring. Since the height error for 147 crossover points on the ice sheet was±6.7m in standard deviation, and height errors from slope-induced effect and other sources were 20m, the contour interval of 100m was chosen for an inland area higher than 500m above sea level. The obtained configuration resembles the map published by the Scott Polar Research Institute (1983). A total of 157 ground survey data from triangulation survey, satellite Doppler positioning and previously published topographic map are used to estimate an overall accuracy of the obtained configuration map. The ground survey height is on an average 2.2m lower than the SEASAT-derived elevation with a standard deviation of ±21.5m, which may reflect the limited data quality of IGDR without retracking correction of the return-pulse waveform. Drawing orthogonals to the contours, ice drainage basins are determined and they are slightly different from the previous ones defined by the over-snow traverse surveys

Processing of sea gravity data using on-line navigational information of icebreaker SHIRASE

The NIPRORI-1 gravimeter of icebreaker SHIRASE was modified so that the ship\u27s navigational data were used in real time. Examples of measurement using the modified system during the 27th Japanese Antarctic Research Expedition are given to show the performance

カイヨウ エイセイ シーサット ノ コウド ソクテイ データ ニ ヨル ナンキョク シュウヘン カイイキ ジオイド ノ ヒョウカ

NASAが打ち上げた海洋衛星シーサットのレーダー高度計による海面高の測定が, 1978年の6月から9月にかけて行われ, 機械精度±10cmという高精度の測定に成功した。このデータを処理することにより, 南緯45°から南極大陸の縁辺までの海面トポグラフィの図化を行った。衛星の軌道誤差が大きいため, その機械精度に反して, 海面高のデータには±5mの誤差が含まれることがわかった。しかし, ロス海やウェッデル海などの湾形の地帯でのジオイドの顕著なへこみや, 東南極沖合のインド洋におけるジオイドのもり上がりなどが, みごとに測られていることもわかった。The SEASAT radar altimetry data, which were obtained during its operational period from June to September 1978,have been processed, and the sea surface topography and/or the geoid in the area between 45°S and the margin of the Antarctic Continent have been contour-mapped. Mainly because of the uncertainty involved in the satellite altitude the sea surface topography includes maximum errors of ±5m. However, some significant features such as geoid depressions at the Ross Sea and the Weddell Sea or the regional geoid upheavals over the Indian Ocean off East Antarctica have been clearly displayed