Outline of the Method of Conducting a Trigonometrical Survey, for the Formation of Geographical and Topographical Maps and Plans: Military Reconnaissance, Levelling, Etc.; with the Most Useful Problems in Geodesy and Practical Astronomy, and Formulæ and Tables for Facilitating Their Calculation
Lockwood and Company, 1873 - 321 стор.
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accuracy accurate acres adjustment altitude apparent ascer ascertained astronomical axis azimuth barometer base beam compass calculated centre chain chronometer circle compass computed contour lines correction degree depression determined diameter difference of longitude direction divisions earth equal feet field-book fixed given Greenwich Greenwich mean ground height hills horizontal hour angle inches index error instrument intersection interval laid latitude length limb lunar lunar distance marked measured mercury meridian method miles moon's Nautical Almanac necessary noon º º object obtained Ordnance Survey paper parallax parallel pickets plane plotted pole portion position purpose radius reading reference refraction right ascension roads scale screw sections semidiameter sextant sidereal sides sketch slopes spherical spherical excess spirit-level staff star stations subtractive surface surveyor Table taken tangent telescope temperature theodolite thermometer tion traced transit triangles trigonometrical points tube vernier vertical wire zenith distance zero
Сторінка 188 - An Account of the Measurement of an Arc of the Meridian, extending from Dunnose, in the Isle of Wight, Latitude 50° 37
Сторінка 124 - ... C, to admit of the thermometer passing through a collar of cork, which shuts up the slit where the thermometer is placed. D. Thermometer, with so much of the scale left out as may be desirable. E. Holes for the escape of steam. The pot is filled four or five inches with pure water ; the thermometer fitted into the aperture in the lid of the sliding tube, by means of a collar of cork; and the tin sliding tube pushed up or down to admit of the bulb of the thermometer being about two inches from...
Сторінка 86 - ... but it may be made in a variety of ways, so as to revolve on any light portable stand. The tube, when required for use, is filled with water (coloured with lake or indigo), till it nearly reaches to the necks of the bottles, which are then corked for the convenience of carriage. On setting the stand tolerably level...
Сторінка 127 - Assuming 30'00 inches as the average height of the barometer at the level of the sea (which is however too much), the altitude of the upper station is at once obtained by inspection of Table I, correcting for temperature of the stratum of air traversed by table II.
Сторінка 1 - ... at each of these points by the base itself. The distances of these stations, from the ends of the base line and from each other, are then calculated, and laid down on paper, forming so many fresh bases from whence other trigonometrical points are determined, until the entire tract of country to be surveyed is covered over with a net-work of triangles of as large a size as is proportioned to the contemplated extent of the survey, and the quality and power of the instruments employed. Within this...
Сторінка 207 - In the orthographic projection, every point of the hemisphere is referred to its diametral plane or base, by a perpendicular let fall on it, so that the representation of the hemisphere thus mapped on its base, is such as it would actually appear to an eye placed at an infinite distance from it. It is obvious, from the annexed figure, that in this projection only the central portions are represented of their true forms, while all the exterior is more and more distorted and crowded together as we...
Сторінка 36 - The triangulation should never be laid down on paper until its accuracy has been tested by the actual measurement of one or more of the distant sides of the triangles as a base of verification, and by the calculation of others from different triangles to prove the identity of the results.
Сторінка 186 - Ocean, the first thing which strikes us is, that, the north-east and south-east monsoons, which are found the one on the north and the other on the south side of the...
Сторінка 77 - BA, the sum of the two refractions ; hence, supposing half that sum to be the true refraction, we have the following rule when the objects are reciprocally depressed. Subtract the sum of the two depressions from the contained arc, and half the remainder is the mean refraction : — If one of the points B, instead of being depressed be elevated, suppose to the point g, the angle of elevation being gA.D, then * " Trigonometrical Survey,
Сторінка 246 - ... correction, with its proper sign. If the sign be +, the correction must be added to the reduced altitude; but if it be — , it must be subtracted : in either case the result will give an Approximate Latitude. With the Altitude and Sidereal Time of observation, take out the second correction, and with the day of the month and the same Sidereal time, take out the third correction.