Geodetic Instruments Research Articles

Seismotectonic framework of the North Tehran Fault

The North Tehran Fault is the principal structure by which the southern flank of the Alborz range was raised about 2 1 2 km above the alluvium of the Tehran embayment. It forms part of a system of small blocks accommodating the NE-SW thrust of the Alborz. The fault is about 35 km long and seems to die out as a single structure in the west and joints the major Musha-Fasham Fault in the east. Displacements are by upthrusting of the Eocene volcanics of the Alborz southwards over the Pliocene-Quaternary alluvium of Tehran, accompanied by a minor left-lateral movement. These displacements started in the Late Pliocene and may still be continuing to-day. Two recent catastrophic earthquakes occurred in 1957 and 1962 in two regions about 135 km from Tehran, in tectonic systems not directly related to the North Tehran Fault. The nearest damaging earthquake occurred in 1930, not far from the point where the North Tehran Fault joins the Musha-Fasham Fault. Seismicity in the 20th century is not controlled by any single major fault, but seems to follow ‘seismotectonic provinces’. Though undamaged since the late 19th century, the Tehran region has experienced some major earthquakes in the past. As in other seismic countries, reverse and thrust-fault activity, is often more difficult to detect than strike-slip by topographic and epicentre locations alone. This was shown recently by the 1971 San Fernando earthquake, California. It is therefore essential that research be pursued, and that adequate geodetic and microseismic instrumentation be installed in the Tehran region and in particular near the North Tehran Fault.

GEODEZIJA VIDURAMŽIŲ LIETUVOJE

Click to increase image sizeClick to decrease image size После разгрома крестоносцев в Жальгиреекай битве (1410 г.) в Лиrовско-Польском государстве определились благоприятные условия для развития научной мысли. Расширились связи с западными государствами, особенно с Италией, откуда пришли римские методы измерения и система некоторых мер. В Вильнюсском и Краковском университетах быстрыми темпами начали развиваться такие науки, как математика и астрономия. Являясь составной частью этих наук, измерения достигли в Литве и Польше высокого качественного уровня. Сведения о применении геодезических методов и инструментов при измерениях, проводимых в связи с земельной реформой Зигманта Августа, можно найти в первом учебнике по геодезии, написанном в 1565 г. Станиславом Гжепским. Важнейшими измерительными инструментамя в XVI веке были экер и в масле пропитанная веревка. В Литве обычно была длиной в 75 аршин (длина литовского аршина равнялась 64,5 см). Гжепский подробно описывает систему мер в Польше, дает много полезных для землемеров советов. Во второй половине XVI века геодезическая и картографическая деятельность в Польше перестала прогрессировать, и очередная карта Польши вышла только 200 лет спустя. В третий раз в Литве же геодезические работы велись интенсивно, территория Литвы картографировалась. Готовилась к выпуску карта М. К. Радвилы (выпущена в 1613 г.). Эта карта по своему качеству и точности отсбражения являлась наиболее точной в тогдашней Европе. Это свидетельствует о том, что геодезические работы в Литве в средневековье находились на высоком уровне. SUMMARY After the defeat of peasants in the battle of Žalgiris in 1410 favourable conditions were created for the intellectual movement in the Lithuanian—Polish state. Relations with Western countries were widened, especially with Staly from which Roman measurement methods and the system of some measures were taken. At the universities of Vilniaus and Kraków mathematics and astronomy began to develop rapidly. Measurements as a part of these sciences were of high standards in Lithuania and Poland. The application of geodetic methods and instruments in measurings performed in conncetion with the Zigmand Augustus' land reform can be observed in the text-book of 1565 writlen by Stanislav Gžepskij. The main measuring instruments of the XVI century were a right—angle mirror and a rope treated with oil. In Lithuania the length of the rope was 75 arshins. The Lithuanian arshin was equal to 64,5 cm. Gžepskij gives a detailed description of the measure system in Poland and a lot of useful advices for measurers. In the second half of the XVI-th century the geodetic and cartographic activities seized progressing as the next map of Poland was produced only after 200 years. But in Lithuania the geodetic works were being carried out more intensely since the territory of Lithuania was being mapped for the third time. The Radvil's map was under production (issuld in 1613). The map was of the highest accuracy in Europe at that time. This fact indicates the high level of geodetic works in Lithuania of the Middle Ages.

HENRY WILD AND DEVELOPMENT IN THE DESIGN AND CONSTRUCTION OF MODERN GEODETIC INSTRUMENTS

The geodetic instruments of the leading firms have so many common basic features that it hardly can be any accident. Obviously this similarity is due to the influence of a man who devoted his life to the development of modern surveying instruments. This man was Dr. Heinrich Wild, from Switzerland (1877–1951). He was a surveyor and carried out triangulation work of all orders, precise levelling measurements and plane-table topographic work. By doing this he learned the difficulties in the instruments available at those times. Through his practical experience in field work he realized that existing geodetic instruments were not designed and constructed to enable the surveyor to work rationally. This led him to improve this equipment, and his success was unique.

Theory of a Polyhedral Heliotrope on an Artificial Satellite

AbstractThe heliotrope, invented by GAUSS, is a geodetic instrument for transmitting signals between distant stations by reflection of solar rays from a small, flat mirror. Many such mirrors on an artificial satellite, forming a polyhedral heliotrope, would automatically send useful signals and greatly increase the satellite visibility.It will be shown that the apparent stellar magnitude of a heliotrope signal is given by m = − 36.85 − 2.5 log10 k \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{D}{\varrho}} \right)^2 \sin \frac{\Theta}{2} $\end{document}, where k is the reflectivity factor, D the effective diameter of the mirror face, ϱ the distance from the observer, and Θ the elongation of the satellite from the sun. Thus, the mean stellar magnitude at opposition from a 1 cm face is about +0.m9 when 500 km away.The theory of the duration and statistical frequency of such flashes from a quasi‐regular polyhedron has been worked out in quantitative form. It turns out that the mean approximate signal rate per second for a polyhedron of radius 25 cm would be \documentclass{article}\pagestyle{empty}\begin{document}$\bar n = \frac{{2{\rm I}\,\omega}}{{D^2 }} $\end{document}, where ω is the number of satellite rotations per second. Thus, there would be 21 flashes per second from a satellite with 1 cm faces rotating once per second, each flash lasting less than 0.s001, which would correspond to about 2′′ or 3′′ of motion on the photographic trail of the satellite.Some such arrangement of the reflecting surface of the satellite is necessary for any study of its rotational motion. Also, it would obviously facilitate all observations during the expected 99% of the satellite lifetime after its radio power has been exhausted.

Use of color‐filters on geodetic instruments

For several years the United States Coast and Geodetic Survey has carried on intermittently a series of experiments with color‐filters on first‐ and second‐order theodolites and first‐order levels in an attempt to improve the appearance of the object pointed upon by eliminating as far as possible the disturbances caused by heat‐radiation and scattering light. It is consistent with Huyghen's theory that the red and yellow filters are found to be the best for absorbing the disturbing lights of the short‐wave length, namely, those approaching the ultra‐violet part of the spectrum.

Recent developments in geodetic instruments

During the past two years there have been a number of improvements and new instruments developed by the United States Coast and Geodetic Survey in its geodetic instrumental equipment. The principal matters, to be mentioned are the completion of a first‐order theodolite, the development of a second‐order instrument of the sane nature, and the improvement in the design and method of graduation of the precise level‐rod.

Geodetic instruments from the viewpoint of the physicist

In connection with my work at the U.S. Bureau of Standards in the calibrating of various geodetic instruments and in the preparing of occasional specifications for instruments of this sort as well as in consequence of my visit to European standardizing laboratories I have become deeply interested in this subject. As I have been fortunate in my opportunities for seeing and working with geodetic instruments in several countries, a brief critical description of a few of these may be of some interest. A discussion of these leads naturally to some remarks on geodetic instrument design, and then to a brief outline of the efforts being made in the Section of Length Measurements at the Bureau of Standards to cooperate in geodetic work.

Scientific Serials

Rivista Scientifico Industriale, No. 13, July 15,—Water in alcoholic fermentation, by Prof. Pasqualis.—On animals which exhale an odour of musk.—New observations and note on Crookes' apparatus, by Prof. Serpieri.—On automatic geodetic instruments, by Prof. Vecchi.