Outline of the Method of Conducting a Trigonometrical Survey, for the Formation of Geographical and Topographical Maps and Plans: Military Reconnaissance, Levelling, EtcWeale, 1850 - 253 pages |
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Page 6
... feet at the level of the sea . The details of the base of verification ( i . e . the actual measurement of the side of a remote triangle , whose length had been previously obtained by calculation ) in Romney Marsh , in 1787 , are also ...
... feet at the level of the sea . The details of the base of verification ( i . e . the actual measurement of the side of a remote triangle , whose length had been previously obtained by calculation ) in Romney Marsh , in 1787 , are also ...
Page 7
... feet long , placed parallel to each other , were riveted together at their centres , it having been previously ascertained , by numerous experiments , that they expanded and contracted in their transitions from cold to heat , and the ...
... feet long , placed parallel to each other , were riveted together at their centres , it having been previously ascertained , by numerous experiments , that they expanded and contracted in their transitions from cold to heat , and the ...
Page 8
... feet being completed in one day , and five boxes , giving a length of 52 feet , being levelled and laid together . About 400 feet of this measured base was across the river Roe , and clumps of pickets were driven at intervals of about 5 ...
... feet being completed in one day , and five boxes , giving a length of 52 feet , being levelled and laid together . About 400 feet of this measured base was across the river Roe , and clumps of pickets were driven at intervals of about 5 ...
Page 9
... feet ; if , then , the log of the base , in feet , be added to the log of the alti- tude , and the log of the sum of the radius and altitude be sub- tracted therefrom , the remainder will be the log of a number to be * " Recueil des ...
... feet ; if , then , the log of the base , in feet , be added to the log of the alti- tude , and the log of the sum of the radius and altitude be sub- tracted therefrom , the remainder will be the log of a number to be * " Recueil des ...
Page 16
... feet in diameter , were used for fixing the principal stations * . The angles at the vertices of the secondary triangles were observed with the second - class theodo- lites . The sides of these triangles were , on an average , about 10 ...
... feet in diameter , were used for fixing the principal stations * . The angles at the vertices of the secondary triangles were observed with the second - class theodo- lites . The sides of these triangles were , on an average , about 10 ...
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Outline of the Method of Conducting a Trigonometrical Survey, for the ... Edward Charles Frome No preview available - 2016 |
Common terms and phrases
accuracy accurate acres adjustment angles of elevation Apparent altitude ascertained astronomical axis azimuth barometer base boundaries calculated centre chain chronometer circle computed contour lines correction course curvature declination degree depression determined difference of longitude direction divisions earth equal feet field-book fixed Géodesie given Greenwich Greenwich mean ground height horizontal line hour angle inches index error instrument intersection interval laid latitude length lunar distance marked mean solar measured meridian method miles Nautical Almanac necessary noon object observed angles obtained Ordnance Survey parallax parallel pickets place of observation plane plotted pole portions position purpose radius reading reference refraction right ascension roads rods scale screw sections semidiameter sextant sidereal sides sketch slopes spherical spherical excess spirit level star stations subtractive surface taken tangent telescope temperature theodolite thermometer tion traced triangles trigonometrical points Trigonometrical Survey tube vane vertical zenith distance
Popular passages
Page 138 - 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...
Page 140 - An Account of the Measurement of an Arc of the Meridian, extending from Dunnose, in the Isle of Wight, Latitude 50° 37
Page 73 - AB, aBA, 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 g AD, then * " Trigonometrical Survey,
Page 74 - BA, the sum of the two refractions ; the rule for the mean refraction then in this case is, subtract the depression from the sum of the contained arc and the elevation, and half the remainder is the mean refraction *. The...
Page 81 - ... 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 by the eye, these corks are both withdrawn, which must be done carefully, and when the tube is nearly level, or the water will be ejected with violence ; and the surface of the water in the bottles, being necessarily on the same level, gives a horizontal line in whatever direction the tube is turned, by which the vane of a levelling staff is...
Page 112 - ... diameter. B, a sliding tube of tin, moving up and down in the pot ; the head of the tube is closed, but has a slit in it, 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...
Page 114 - 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.
Page 158 - 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...
Page 114 - When the boiling point at the upper station alone is observed, and for the lower the level of the sea, or the register of a distinct barometer is taken, then the barometric reading had better be converted into feet, by the usual method of subtracting its logarithm from 1-47712 (log. of 30 inches) and multiplying by '0006, as the differences in the column of " barometer " vary more rapidly than those in the ''''feet
Page 14 - heliotrope," which is a piece of looking-glass, so adjusted as to reflect the sun directly to any desired point, is the most perfect arrangement. For night signals, an Argand lamp is used ; or, best of all, Drummond's light, produced by a stream of oxygen gas directed through a flame of alcohol upon a ball of lime. Its distinctness is exceedingly increased by a parabolic reflector behind it, or a lens in front of it. Such a light was brilliantly visible at 66 miles distance. (385) Observations of...