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 14
... necessary for the assistant , who is posted as near as possible to the station , to keep the enlightened object in the focus of the telescope , and the mirror is adjusted instrumentally so as to always reflect them upon the station and ...
... necessary for the assistant , who is posted as near as possible to the station , to keep the enlightened object in the focus of the telescope , and the mirror is adjusted instrumentally so as to always reflect them upon the station and ...
Page 21
... necessary . In the triangle ABC , suppose C the station where the in- strument cannot be set up . If at any convenient point D , the angles ADB and ADC are taken , and the distance CD measured , the angle ACB can be thus determined ...
... necessary . In the triangle ABC , suppose C the station where the in- strument cannot be set up . If at any convenient point D , the angles ADB and ADC are taken , and the distance CD measured , the angle ACB can be thus determined ...
Page 23
... necessary that every person using a theodolite should be able to replace them himself . They must be stretched tight across the diaphragm , and confined in their places ( indicated by faint notches on the metal ) by gum , or varnish ...
... necessary that every person using a theodolite should be able to replace them himself . They must be stretched tight across the diaphragm , and confined in their places ( indicated by faint notches on the metal ) by gum , or varnish ...
Page 24
... necessary to obtain this ad- justment perfectly ; and the level should be at the same time ad- justed laterally , so as to be in the same vertical plane as the line of collimation , if it should be found , on moving the telescope ...
... necessary to obtain this ad- justment perfectly ; and the level should be at the same time ad- justed laterally , so as to be in the same vertical plane as the line of collimation , if it should be found , on moving the telescope ...
Page 25
... necessary to take into account the corrections for refraction and the curvature of the earth , depending upon the arc of distance , which subjects will be explained hereafter ; but for the purpose of ascertaining the index error of the ...
... necessary to take into account the corrections for refraction and the curvature of the earth , depending upon the arc of distance , which subjects will be explained hereafter ; but for the purpose of ascertaining the index error of the ...
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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 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 stations subtractive surface taken tangent telescope temperature theodolite thermometer tion traced transit triangles trigonometrical points Trigonometrical Survey tube vane vertical zenith distance
Popular passages
Page 169 - A Solar Day is the interval of time between two successive transits of the sun over the same meridian; and the hour-angle of the sun is called Solar Time.
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 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 73 - 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,
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 181 - Call the zenith distance north or south, according as the zenith is north or south of the object.
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...