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 CalculationJohn Weale, 1850 - 253 pages |
From inside the book
Results 6-10 of 38
Page 24
... parallel to the optical axis , and to the surface of the cylindrical rings on which it is supported ; this is done by simply levelling the telescope by means of the tangent screw to the vertical arc , and then reversing it end for end ...
... parallel to the optical axis , and to the surface of the cylindrical rings on which it is supported ; this is done by simply levelling the telescope by means of the tangent screw to the vertical arc , and then reversing it end for end ...
Page 34
... parallel ruler or angle ( if the angle and ruler be preferred ) is stretched across its diameter to the opposite corresponding angle , the zero having been first laid on the meridian line and moved forward to the point from whence the ...
... parallel ruler or angle ( if the angle and ruler be preferred ) is stretched across its diameter to the opposite corresponding angle , the zero having been first laid on the meridian line and moved forward to the point from whence the ...
Page 42
... parallel lines running up the page , with the offsets written on the right and left of these lines as in the example facing page 36 , or on a species of diagram bearing some sort of resemblance to the outline of the ground to be ...
... parallel lines running up the page , with the offsets written on the right and left of these lines as in the example facing page 36 , or on a species of diagram bearing some sort of resemblance to the outline of the ground to be ...
Page 43
... parallel lines at measured intervals , as well as for other purposes . The offset and plotting scales , introduced by Major Robe on the Ordnance Survey , are as present so many known fixed stations between the measured lines OF SURVEY . 43.
... parallel lines at measured intervals , as well as for other purposes . The offset and plotting scales , introduced by Major Robe on the Ordnance Survey , are as present so many known fixed stations between the measured lines OF SURVEY . 43.
Page 45
... parallel to the meridian , and the observed bearing being marked * In using reflecting instruments , avoid very acute angles , and do not select any object for observation which is close , on account of the parallax of the instrument ...
... parallel to the meridian , and the observed bearing being marked * In using reflecting instruments , avoid very acute angles , and do not select any object for observation which is close , on account of the parallax of the instrument ...
Common terms and phrases
accuracy accurate acres adjusted angles of elevation Apparent altitude approximate ascertained astronomical axis azimuth barometer base boundaries calculated centre chain chronometer circle compute contour lines correction course curvature declination degree depression determined difference of longitude direction division earth equal equator feet field-book figure fixed formula geodesical Géodesie given Greenwich Greenwich mean ground height hour angle inches index error intersection interval laid land latitude length lunar distance marked mean solar measured meridian method miles moon's Nautical Almanac necessary object obtained operation 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 subtractive sun's surface surveyors taken tangent telescope temperature theodolite thermometer tion transit triangles trigonometrical points Trigonometrical Survey tube vertical zenith distance
Popular passages
Page 180 - PS, the polar distance, and the angle at P are known, and ZP, the co-latitude, is the quantity sought. The formula given by Baily, for finding the third side, when the other two sides and an angle opposite to one of them are given, is tan a' == cos given angle x tan adjacent side
Page 147 - Both these projections may be considered natural ones, inasmuch as they are really perspective representations of the surface on a plane; but Mercator's projection is entirely an artificial one, representing the sphere as it cannot be seen from any one point, but as it might be seen by an eye carried successively over every part of it.
Page 156 - represent the equinox, rT will be the right ascension, TS the declination, and PS the polar distance of any star or object S, referred to the equinoctial by the hour circle PSTp; and BSD will be the diurnal circle it will appear to describe about the pole. Again, if we refer it to the horizon by the vertical circle
Page 101 - 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 the bottom of the pot.
Page 126 - solely to establish the truth of this supposition, the account of which is published in the " Philosophical Transactions " for 1775. A distance of upwards of 4000 feet was accurately measured between two stations, one on the north and the other on the south side of a mountain in Perthshire. The difference of latitude between these extremities of the measured distance was, from a number of most careful observations, determined to be
Page 71 - required for use, is filled with water (colored 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 by the eye, these corks are both withdrawn
Page 155 - 0 35 These definitions are rendered more evident by reference to the figure below, taken from Sir J. Herschel's Treatise on Astronomy, published in the Cabinet Cyclopaedia. " Let C be the centre of the earth, NCS its axis; then are N and S its poles; EQ its equator; AB the parallel of latitude of the station A on its surface; AP, parallel to
Page 146 - diametral plane ADF perpendicular to EB by the visual line PM E. The stereographic projection of a sphere, then, is a true perspective representation of its concavity on a diametral plane; and as such it possesses some singular geometrical properties, of which the following are two of the principal:—first, all circles on the sphere are represented by circles in the projection; thus the
Page 153 - always additive. This term, as applied in its limited sense to altitudes of celestial objects, is meant to express the angle subtended by the semi-diameter of the earth at the distance of the object observed. Altitudes of the moon, from her proximity to the earth, are most
Page 41 - ac=AC aD=AD To measure the distance between A and B, both being inaccessible :—From any point C draw any line Cc bisected in D ; take any point E in the prolonga'tion of AC, and join ED, producing