巻号一覧
18 巻 (1972)
- 4 号 p. 161-
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18 巻, 4 号
選択された号の論文の7件中1～7を表示しています
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萩原 幸男1972 年 18 巻 4 号 p. 161-171
発行日: 1973/03/25
公開日: 2011/03/01
ジャーナル フリーMolodenskii's solution of the geodetic boundary-value problem is approximately derived by means of G1, a kind of terrain correction to gravity anomaly. Although many geodesists have theoretically discussed G1 since Molodenskii's problem was introduced, a very few reports of practical computation of G1 have been presented. In the present paper, the author practically obtains G1 using the gravimetric and terrain data of Tanzawa Mountains. The conclusions obtained here are summarized as follows: (a) In numerical computations of G1, an integration range of 20 km from gravity station can effectively suppress errors under 0.5 mgals In case of a gently-sloping hill, an integration with a range of 10 km works well in accurately calculating G1. (b) The contribution of the inner zone of the integration range to G1 is so large, that detailed maps of topography and gravity anomaly in the inner zone are necessary for data-reading with high accuracy. (c) Gi mirrors short-wavelength free-air gravity or terrain relief. G1 can also be approximated by a quantity proportional to the vertical gradient of gravity (free-air) anomaly. (d) Assuming as a rough estimate, we see that G1 produces errors of about 6 cm at maximum in the height anomaly and about 10 sec in the gravimetric deflection of the vertical on Tanzawa Mountains. The error estimated in the deflection of the vertical is not small as compared with the astrogeodetic deflections observed in the neighborhood of this area.抄録全体を表示PDF形式でダウンロード (971K) -
井内 登, 佐藤 裕1972 年 18 巻 4 号 p. 172-179
発行日: 1973/03/25
公開日: 2011/07/05
ジャーナル フリーThe sea-crossing levelling on Uraga Channel was carried out in September 1972 by the Geographical Survey Institute. One of the error sources of the measurement, which was made by th e way of trigonometric levelling, is the effect of the vertical deflection, that is the correction due to the geoid curvature. In this paper, the effect of the vertical deflection is discussed, standing in another point of view by Ramsayer.
The vertical deflection depends on the curvatures of the geoid and the ellipsoid, then, the curvature correction can be deduced from the vertical deflection.
When the curvature is a function of distances, the error is expressed by the formula, dh=1/6 q′/q2 S3, where q is the curvature of the geoid, q' is its first derivativeq and s is the distance between observed stations. In the case of the sea-crossing levelling on Uraga Channel whose distance is about 6.7 km, the error (dh) is estimated to be 2.8 mm. In the calculation, the vertical deflections of levelling stations were obtained by the interpolation method of the vertical deflection, using gravity anomalies data of Kanto district. It should be mentioned, however, that the error is concerned to the distance cubed (S3), so it has serious problems in the survey of long distance amounting to 30 km, such as on Tsugaru Channel.抄録全体を表示PDF形式でダウンロード (621K) -
藤井 陽一郎, 中根 勝見1972 年 18 巻 4 号 p. 180-190
発行日: 1973/03/25
公開日: 2011/03/01
ジャーナル フリーIn a previous paper, one of the present authors estimates the rate of secular change of gravity at 0.817, cgal/year along the high gravity anomaly zone in South-Western Japan, with some discussions on the interaction of oceanic lithosphere of the Philippine Sea Plate and continental lithosphere of the South-Western Japan . In comparing this order estimation with actually observed gravity change, we must notice the possibilitythat the observed gravity change can be several times higher than estimated one, because the estimated change is the mean value for long time geological duration andthe contemporary change is interseismic one. This point is first discussed in the presentpaper based on the observed crustal deformation accompanied by plates interaction, and some attempts were made to detected secular change of gravity along the northernboundary of the Philippine Sea Plate by a comparison of old and new observed gravityvalues. After analysing the various kinds of errors included in the gravity surveys that were carried out by the Geographical Survey Institute, we can conclude that the ob erved secular change of gravity of +0.13+0 .18 mgals for past ten years at the southern parts of Kii Peninsula and Muroto Promontory is real one. Detected secular changes of gravity at each gravity stations in those regions become gradually higher as the stations locate more close to the southern point of promontory in concordance with the distribution of Bouguer anomalies. This fact means that the high gravity anomalies found in the peninsula or promontory along the northern boundary of the Philippine Sea Plate are being formed even at contemporary time. In conclusion, the authors emphasize that the more study of secular change of gravi y accompained by plates interaction should be tried as one of the most important problems of geodesy in tectonic area such as Japan Island.抄録全体を表示PDF形式でダウンロード (1261K) -
原田 健久1972 年 18 巻 4 号 p. 191-193
発行日: 1973/03/25
公開日: 2011/07/05
ジャーナル フリー(1)準拠楕円体の形と大きさは偏平率fと長半径aで決まる. (2)準拠楕円体と地球との向きの関係は,準拠楕円体の回転軸と零度子午面を地軸(1900-1905のmean poleの方向)と天文零度子午面とにそれぞれ平行にすることで決まる. (3)この準拠楕円体を平行移動させて,測地原点座標(経度λ0,緯度ψ;O,高さh0)で示される点を現実の測地原点と一致させれば,準拠楕円体と地球との最終的な関係が決まる. (2)の条件は測地網の中にある多くのLaplace点でLaplace条件がより良く満足されるようにすることによって達成される.そのような手段によって決められた測地原方位角にも,そのもとになった天文方位角の観測がnon errorでない限り幾分かのerrorが残る.このerrorが(2)の条件を擾乱する. (2)の条件が満足されていないと,準拠楕円体の変換に伴う測地座標の変換には座標軸の回転がはいる. (2)の条件は満たされているとして,2つの異なる準拠楕円体A,Bを考えれば,Aの中心とBの中心を通る直交座標軸は平行である.そして現実の測地原点に対しては2組の測地座標(λ0A, ψ0A,h0AまたはX0A,Y0A,Z0A)(λ0B, ψ0B,h0BまたはX0B,Y0B,Z0B)がある. ΔX0=X0B-X0A, ΔY0=Y0B-Y0A, ΔZ0=Z0B-Z0AはA直交座標からB直交座標への平行移動量に他ならない.この量はまた任意の地点におけるAとB両直交座標の差でもある.従つて( Δλ0, Δψ0, Δh0)または(ΔXi, ΔYi, ΔZi)が既知なら任意の点の(λiA, ψiA,hiA)を(λiA, ψiA,hiA) →(XiA,YiA,ZiA) →(XiA+ ΔX0=XiB, … ) →(λiB,ψiB,hiB)の順序でB測地座標に厳密に変換できる. 今回，各計算を12桁精度で行なう実用的にはnon-errorのプログラミングを完成した.どうぞ御利用下さい. 地球の大きさに関する知識の前進と世界にばらまかれている15ヶめBaker Nunnカメラによる人工衛星の観測から,より良い地球楕円体とその楕円体に基いたBaker Nunnカメラの位置が見出されつつある.[2].この世界測地座標系と日本測地座標系は三鷹のBaker Nunnを仲介にして関係づけられている.著者の以前の研究によれば,我hが現在公式に使用している日本測地座標系には殆ど原方位誤差がない.[1].各種の世界楕円体に対する ΔX, ΔY, ΔZが与えられれば上述のプログラムにより原点座標に加えるべき修正値を見出すことができる.表はその値である.Δλ0, Δψ0がほぼ一定値に収歛しているのに対して Δhgo。(原点における準拠楕円体表面からgeoidまでの高さ,現在のhgoは零)は決まりにくい量のようである.抄録全体を表示PDF形式でダウンロード (291K) -
田中 寅夫1972 年 18 巻 4 号 p. 194-201
発行日: 1973/03/25
公開日: 2011/03/01
ジャーナル フリーEffects of oceanic tides on the earth tides observed at Barim in China, and Kamigamo, Osakayama, Kishu and Rokko in Kinki District, Japan have been estimated in a similar way as in the previous report. The effect of change of gravitational field caused by the mass re-distribution of the earth deformed by surface load, on the vertical deflection, has been taken into consideration, for oceans locating at distances farther than 30°, the Green′s function by I. M. longman has been used, and in the case of neighbouring sea (0<30°), the above effect has been estimated together with the attraction of loading sea water mass, according to the way by E. Nishimura, who calculated the amount of the vertical deflection, representing the total effect by (1-n) A (A being the vertical deflection by attraction of water mass) with the coefficient 1-n of 0.5. The diminishing factor γ obtained by Nishimura at Barim has been re-examined. If 1-n is taken to be 0.7, then γ of the EW component becomes to 0.69, which agrees fairly well with that expected for the Gutenberg earth model. Similar results have also been obtained for Kamigamo and Osakayama, from which we may conclude that n is about 0.3, which agrees well with the result by l. Rosenhead. In several components of earth tidal tilts and strains at Kamigamo, Osakayama, Kishu and Rokko, there are some remarkable discrepancies between the observed values and those calculated for the Gutenberg earth model. The reasons for them are discussed.抄録全体を表示PDF形式でダウンロード (1094K) -
中井 新二, 佐藤 範雄1972 年 18 巻 4 号 p. 202-208
発行日: 1973/03/25
公開日: 2011/03/01
ジャーナル フリーRecent gravity survey has proved that the Morioka-Sirakawa (Shirakawa) line, which locates on the western rim of Kitakami and Abukuma mountains and shows the characteristic steep gradient of Bouguer anomalies, is very clear near Mizusawa . Two dimensional analyses along the profile A (Fig.1) were made and the crustal section as shown in Fig. 5 has been obtained. This section is consistent with the geological and seismological points of view. The Morioka-Sirakawa line seems to reflet the faultlike structure of the upper crust.抄録全体を表示PDF形式でダウンロード (1287K) -
笠原 慶一1972 年 18 巻 4 号 p. 209-213
発行日: 1973/03/25
公開日: 2011/03/01
ジャーナル フリーPDF形式でダウンロード (497K)
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