## 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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**true**horizontal value . The length of a base , which has subsequently to be determined with the most minute accuracy , by means of glass rods , compensation bars , or other contrivance , is generally first measured two or three times in ... Page 25

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**true**reading of the angle ; this me- thod has , however , been objected to as being incorrect in principle , an B undue importance being given to the reading of the vernier A , and also in a smaller degree to B. The influence assigned ... Page 58

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**true**military character , or the power of delineating them with ease , rapidity , and correctness . The instruments used in sketching ground have already been alluded to when describing the mode of filling in the detail between measured ... Page 70

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**true**level ; but the apparent level ( and of course , the apparent altitude or depression ) is vitiated by these two causes of error , curvature and terrestrial refraction ; the correction for the first of which depends upon the " arc ... Page 71

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**true**and apparent level . Then ( r + x ) 2 = r2 + t2 . B t 30 a Whence x ( 2r + x ) = t2 ; and , owing to the small proportion that any distance measured on the surface must bear to the earth's radius , 2r may be substituted for ( 2r + ...### Other editions - View all

Outline of the Method of Conducting a Trigonometrical Survey, for the ... Edward Charles Frome No preview available - 2016 |

### Common terms and phrases

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 divisions 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 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...