Outline of the Method of Conducting a Trigonometrical Survey, for the Formation of Geographical and Topographical Maps and Plans: Military Reconnaissance, Levelling, Etc |
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Page viii
Correction for Curvature of the Earth - for Refraction . - Average Amount of these Corrections . - Reciprocal Angles of Depression and Elevation for determining the Amount of Refraction at any particular period .
Correction for Curvature of the Earth - for Refraction . - Average Amount of these Corrections . - Reciprocal Angles of Depression and Elevation for determining the Amount of Refraction at any particular period .
Page x
TO DETERMINE THE AMOUNT OF THE SEVERAL CORRECTIONS FOR REFRACTION , PARALLAX , & c . . 175 III . TO DETERMINE THE LATITUDE . 1. By Observations of a circumpolar Star at the time of its Upper and Lower Culminations . 2.
TO DETERMINE THE AMOUNT OF THE SEVERAL CORRECTIONS FOR REFRACTION , PARALLAX , & c . . 175 III . TO DETERMINE THE LATITUDE . 1. By Observations of a circumpolar Star at the time of its Upper and Lower Culminations . 2.
Page xi
Table of Refractions 5. Contraction of semi - diameters of the Sun and Moon from Refraction 6. Semi - diameter of the Sun . 231 234 . 234 7. Augmentation of semi - diameter of the Moon , with her increase in altitude • 10.
Table of Refractions 5. Contraction of semi - diameters of the Sun and Moon from Refraction 6. Semi - diameter of the Sun . 231 234 . 234 7. Augmentation of semi - diameter of the Moon , with her increase in altitude • 10.
Page 13
Observations may be made on a station which would be hid by intervening high ground were it not elevated above its real place by refraction , but periods should always be chosen for observing angles when extraordinary refraction is not ...
Observations may be made on a station which would be hid by intervening high ground were it not elevated above its real place by refraction , but periods should always be chosen for observing angles when extraordinary refraction is not ...
Page 25
If the distance selected be too long , it becomes 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 ...
If the distance selected be too long , it becomes 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 ...
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accuracy accurate Additives adjustment altitude angle apparent applied approximate ascertained axis azimuth barometer base boundaries calculated centre chapter chronometer circle compared construction contained contents contours correction course declination depression described detail determined difference direction distance division drawn earth elevation equal error evidently feet figure fixed given gives ground half height horizontal hour inches instrument intersection interval known laid land latitude latter laying length longitude marked mean measured meridian method miles minute nature nearly necessary noon object observed obtained operation parallax parallel plane plotted pole portions position practical proportion quantity reading reference refraction represented roads scale screw sidereal sides sketch spherical star stations supposed surface survey taken taking telescope temperature theodolite thermometer tion traced triangles trigonometrical true 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...
Bibliographic information
| Title | Outline of the Method of Conducting a Trigonometrical Survey, for the Formation of Geographical and Topographical Maps and Plans: Military Reconnaissance, Levelling, Etc |
| Author | Edward Charles Frome |
| Edition | 2 |
| Publisher | Weale, 1850 |
| Original from | Harvard University |
| Digitized | 1 Oct 2007 |
| Length | 253 pages |
| Export Citation | BiBTeX EndNote RefMan |