Order Triangulation Research Articles

“Sucha Góra” (“Trockenberg”)—The Triangulation Point Doomed to Be Forgotten?

The current study documents the importance of research on preserved artifacts which were previously used to take measurements of the Earth, and their importance for cultural heritage. The article reviewed the available source documents presenting the history of the astrogeodetic control point of Sucha Góra-Trockenberg as a monument of the first order triangulation network, preserved in cartographic materials and as the starting point of local geodetic networks, used in mining until 2000 in the so-called Upper Silesian Coal Basin, located in the territory of Poland and the Czech Republic. In order to determine the history of the triangulation work and the dates that the geographic coordinates of the peak were determined, field journals and other available materials were analyzed. The interesting location of this astrogeodetic control point, being in the vicinity of a UNESCO site, as well as its location in a forest and park complex, justify undertaking activities related to the conservation and promotion of this cultural heritage site.

Deformation analysis in central west Bulgaria using triangulation and GPS data

Abstract The article discusses a method applied for combining the results of Global Navigation Satellite Systems (GNSS) and 75-year old triangulation measurements to estimate the crustal movements in central western Bulgaria region. It was examined for joint analysis based on the results of GNSS with angular measurements of the first order triangulation network in Bulgaria during the period 1923–1930 year. As a result of the processing of GNSS and angular measurements, horizontal velocities of 15 points, strain rates, and rotation rates have been obtained. The results show dominating N–S extension at a rate of 1–2 mm/y and the deformation is not uniformly distributed over the studied area. The obtained results indicate the possibility of using old angular measurement of first-order triangulation points, together with GNSS data, to obtain estimates of the horizontal crustal movements.

一等三角点を用いた数値地図50m メッシュ（標高）データの精度の検証

一等三角点を用いた数値地図50m メッシュ（標高）データの精度の検証

Comparison of the Hungarian first order triangulation network with the national GPS network using scale and azimuth differences

While the cadastral and topographic maps tie to the classical reference systems and frames, there will be need to know the relation between the classical and GPS-based networks in a particular country. In this study we discuss the scale factor and azimuth discrepancies between the Hungarian first order triangulation and the national GPS network emphasising their practical significance.The comparison of traditional and GPS derived slope and geodesic distances as well as the comparison of the different azimuths make possible the estimation of the scale and orientation differences of the two systems without the knowledge of height and geoid information which may contain additional errors, too.The estimated −4.34 mm/km mean value reflects the significant scale difference, which is similar to the values derived in neighbour countries. The −2.51 arcsec mean azimuth difference reflects the orientation of the two system.

Recent horizontal deformation of the Japanese Islands deduced from the displacements of first order triangulation stations(<Special issue>Tectonic process and its deep factor in the continental margin of East Asia and the Pacific Ocean)

Recent horizontal deformation of the Japanese Islands deduced from the displacements of first order triangulation stations(<Special issue>Tectonic process and its deep factor in the continental margin of East Asia and the Pacific Ocean)

Detailed horizontal crustal movements associated with the 1923 Kanto earthquake as deduced from network adjustment of old data including the third order triangulation stations

The crustal movements associated with the 1923 Kanto, Japan, earthquake of magnitude 7.9 are deduced from the results of network adjustments with the pre-seimic and post-seismic geodetic data including up to the third order triangulation. The average spacing of the third triangulation is 4 km of higher density as compared with the first order triangulation and the second order triangulation, so we can expect to find much more detailed behavior of the released crustal strain. The main rupture of the 1923 Kanto earthquake that had occurred in the Sagami Bay has been estimated from the crustal deformations deduced from repetition of the first order triangulation and the second order triangulation, while the detailed deformations associated with the secondary faulting are deduced for the first case from the repeated third order triangulation. We find evidence for the secondary faultings in the south Kanto district, Japan, mainly from the pattern of the released strain with the order of 10 −4 and some of them are associated with the surface breakages. We carefully investigate whether these secondary faultings had originated with fracturing at the depth or not. We cannot find any evidence for deep fracturing, though we find remarkable high earth strain release along some secondary faultings. This is mainly due to the fact that the area of high released strain is very limited and narrow along the direction perpendicular to the faulting.

Geodetic strain in peninsular Italy between 1875 and 2001

We determine geodetic strain in peninsular Italy by the GPS reoccupation of the first order triangulation network of Italy installed from 1860. The uncertainties in the original measurements (about 3 ppm), and the time span between the two observations, imply that tectonic signals larger than about 0.03 ppm/yr are resolvable. Along the Apenninic belt, where the largest earthquakes are concentrated, the geodetic deformation has a clear and consistent strain pattern between adjacent regions, well above the uncertainties, and shows a pervasive NE‐SW extension. Along the Tyrrhenian and Adriatic coasts the geodetic signal is not homogeneous and is comparable with the uncertainty in the original measurements. Seismic deformation, calculated over the same time interval, agrees well with estimated extensional direction, but the magnitudes of geodetic and seismic strain differ suggesting that, in part of the Apennines, significant strain accumulation over the past 130 years may not have been released in earthquakes.

EFFECTS OF LARGE VERTICAL DEFLECTIONS IN A HIGH PRECISION NETWORK

AbstractThe purpose of this study is to investigate the effects of very large vertical deflections in a high precision network. The paper focuses on those effects of the vertical deflections which are often ignored or mistreated and errors owing to the use of approximate reductions and predicted astrogeodetic vertical deflections at stations. Part of the Taiwan Geodetic Datum of 1980 (TGD80) first order triangulation network has been the source of the data used to investigate the effects. With the proper reduction equations, all terrestrial observations were first adjusted with a GPS determined geodetic baseline and azimuth in a combination adjustment (Group 1), and then all directions, distances and astronomic azimuths were adjusted together without GPS information (Group 2). The results obtained in this study show that the astronomic station which had the largest vertical deflections in TGD80, creates a maximum position error of 14.2 cm when the rigorous Laplace equation was replaced by the simplified L...

測地測量により求めた日本列島の地震間の平均的な地殻水平歪速度 (I)

Average horizontal crustal strain rates during interseismic period in the Japanese Islands, except the Hokkaido district, are deduced from precise geodetic survey, which has been conducted since the Meiji era. First, distance change rates between the first order triangulation stations are calculated using the weighted least squares method. In regions which suffered from disastrous earthquakes or volcanic eruptions, data before the events are neglected in the above calculation. Second, strain rates in arbitrary triangular regions are estimated.The estimated strain rates ate less than 6×10-7/yr, which is greater than those derived from seismic moment release rate or displacements of active faults. The Japanese Islands may be divided into several provinces on the basis of disstribution of strain rates. In the Tohoku district, a N-S to NE-SW extension is prevailing, and there is a zone of small strain rates which runs parallel to the Oga-Ojika tectonic line proposed by MOGI (1985). This zone may be a boundary between crustal blocks. In the northern Kanto district, strain rates are very small, while a NW-SE compression is predominant in the southern Kanto district. These facts indicate that compressional forces due to the subduction of the Philippine Sea plate may not be transmitted to the northern Kanto district. There is a zone of large compression which runs from Niigata to Gifu through Matsushiro. These high strain rates show a good correlation with seismic activity in the crust. Although compressional strain rates are prevailing in both the Chubu and the Kinki-Chugoku districts, principal axes abruptly change their directions from NW-SE to E-W at around lake Biwa. The westernmost Chugoku and the northern Kyushu districts are characterized by small extension, which suggests that compressional stress predominant in the Chubu and the Kinki districts may fade out. In the Shikoku district, NW-SE compressional strain rates are prevailing. However, temporal variations in baseline lengths show that the elastic rebound associated with the 1946 Nankaido earthquake did not occur in the western part of shikoku. It is considered that the coupling between the subducting Philippone Sea and the overriding Eurasia plates may vary significantly from east to west. Large N-S trending extensions appear in the central Kyushu district, which is consistent with the spreading of the Beppu-Shimabara graben.

Precise alpine geoid determination without digital terrain models

The short wavelength geoid undulations, caused by topography, amount to several decimeters in mountainous areas. Up to now these effects are computed by means of digital terrain models in a grid of 100–500m. However, for many countries these data are not yet available or their collection is too expensive. This problem can be overcome by considering the special behaviour of the gravity potential along mountain slopes. It is shown that 90 per cent of the topographic effects are represented by a simple summation formula, based on the average height differences and distances between valleys and ridges along the geoid profiles, δN=[30.H.D.+16.(H−H′).D] in mm/km, (error<10%), whereH, H′, D are estimated in a map to the nearest 0.2km. The formula is valid for asymmetric sides of valleys (H, H′) and can easily be corrected for special shapes. It can be used for topographic refinement of low resolution geoids and for astrogeodetic projects. The “slope method” was tested in two alpine areas (heights up to 3800m, astrogeodetic deflection points every 170km 2) and resulted in a geoid accuracy of ±3cm. In first order triangulation networks (astro points every 1000km 2) or for gravimetric deflections the accuracy is about 10cm per 30km. Since a map scale of 1∶500.000 is sufficient, the method is suitable for developing countries, too.

4. In situ stress measurements in the Japanese islands: Over-coring results from a multi-element gauge used at 23 sites

The authors have developed a new over-coring stress relief method with a multi-element strain gauge. The new gauge has been used to estimate in situ stress at more than 20 sites for electric power stations in Japan. The results of in situ stress measurements obtained by the method exhibit a general tendency that the maximum compressive principal stress acts horizontally and the horizontal to vertical stress ratio exceeds 1.0. The directions of maximum horizontal compressive in situ stress obtained by the method seem to be consistent with those of the geodetic strains calculated from first order triangulation survey data, and with those estimated from the distribution of tectonic zones which have become active in the Quaternary period. The Japanese islands are located in a tectonically active region, i.e. they are situated near the eastern boundary of the Asian plate towards which both the Philippine Sea plate and the Pacific plate advance. For further detailed discussion a more refined analysis would be required; however, the in situ stress in the Japanese islands is likely to have been significantly affected by these crustal movements.

千葉県富津市における水圧破壊法による地殻応力測定

Using the hydrofracturing technique, in-situ stress measurements have been made in a 450-m-deep well drilled through silty mudstone (the Miocene). Stress has been measured at ten points between depths of 101 and 437m.Data show a steady increase with depth for both maximum (σH max) and minimum (σH min) horizontal compressive stresses, from 33 to 136 bars, and from 20 to 85 bars, respectively.A borehole televiewer and an impression packer are used to detect new fractures created by the hydrofracturing, which indicate the azimuth of σH max. The impression packer detects new fractures more clearly than the borehole televiewer. The direction of σH max is N45°±10°W. This direction does not agree with those estimated from joints which have been developed in the Neogene formations (the maximum compressive stress axis is N-S or vertical), and tectonic strain analyzed from the first order triangulation survey (the maximum compressive strain axis is N-S). But the hydrofracturing result agrees well with the nothwestward motion of the Philippin Sea plate relative to the Asian plate.

Doppler — European Datum transformation parameters for the North Sea

The positioning of platforms and other constructions at distances greater than 100 km offshore is usually carried out by using the Navy Navigation Satellite System (N. N. S. S.) if high absolute accuracy is required. For legal and technical reasons, these positions must be related to the local onshore geodetic datum, usually European Datum 1950 (ED 50). The relation between satellite datum, World Geodetic Datum 1972, and ED 50 must therefore be determined with adequate accuracy. When accuracies of better than 5 m are required, inconsistencies occur owing to a systematic deviation between the British and Norwegian primary order triangulation. This paper gives a review of existing parameters, mainly for the Norwegian side, and describes how they were determined, how they should be used and how errors can be avoided.

Re-evaluation of Horizontal Displacements of Second Order Triangulation Stations associated with the 1923 Kanto, Japan, Earthquake

Re-evaluation of Horizontal Displacements of Second Order Triangulation Stations associated with the 1923 Kanto, Japan, Earthquake

Shoreline Changes Between Phillips Inlet and Pensacola Inlet, Northwest Florida Coast: ABSTRACT

ABSTRACT U.S. Coast and Geodetic Survey topographic and hydrographic surveys and U.S. Geological Survey topographic maps were used to measure erosion and deposition along the northwest Florida Gulf of Mexico coast between Phillips Inlet and Pensacola Inlet. Using first and second order triangulation stations as reference points, no significant net shoreline change could be measured along the so-called and long-recognized eroding coast between Phillips Inlet and Destin. The maximum-possible net erosion rate for this region is the joint error or uncertainty of the compared surveys: a) 1.9 meters/year for the interval 1934-1969, and b) 0.7 meters/year for the interval 1872-1969. No significant net shoreline change could be measured, using the above mentioned technique, for the Santa Rosa Island coast between East Pass and Pensacola Beach. Again, the joint error of the compared maps limits the average, net shoreline change to less than 1.45 meters/year for the 1934-1969 interval. The only portion of Santa Rosa Island for which significant net erosion could be measured is between Pensacola Beach and the U.S. Coast Guard station. The maximum, average erosion rate is 1.3 ± 0.5 meters/year for the interval 1856/1859 to 1965; however, no significant change could be measured for this region over the 1934-1965 interval. The western tip of Santa Rosa Island has experienced net deposition since 1856; using bathymetric charts surveyed in 1881 and 1919, an average deposition rate of 106,000 m1/year plus or minus 15-20% was measured.

Adjustment of a chain of doubly-braced quadrilaterals of measured sides in projection co-ordinates

Summary THE CIRCUMSTANCE is a chain of quadrilaterals begun from and terminating at lines of a 1st Order triangulation; it is assumed that no angles have been measured and that the lengths of all lines in the chain, including redundant diagonals, have been measured.

The significance of the Laplace Stations in Primary Geodetic Network

Abstract The co-ordinates of points determined by geodetic means usually show discrepancies with those obtained astronomically. Comparing, for instance, 1st Order Astronomic co-ordinates with those of a 1st Order Triangulation, the difference can be clearly seen.

Report on the First order Triangulation at Tsushima Area

Report on the First order Triangulation at Tsushima Area

Erratum to: Revision of the first order triangulation in the region disturbed by the Nankaido Earthquake of 1946

Erratum to: Revision of the first order triangulation in the region disturbed by the Nankaido Earthquake of 1946

Revision of the first order triangulation in the region disturbed by the Nankaido Earthquake of 1946

Nach dem Erdbeden von Nankaido im Jahre 1946 hat man das Dreiecksnetz I. Ordnung in einem Gebiet von etwa 300 km Umkreis wiederbeobachtet, und zwar auf 47 Punkten insgeasamt 68 Winkel.