Elements of Surveying: With the Necessary TablesJ. & J. Harper, 1830 - 306 páginas |
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Página 37
... paper . 65. The earth being spherical , its surface is curved , and every line traced accurately on the surface , is also curved . 66. If large portions of the earth's surface are to be measured , such as states and territories , its ...
... paper . 65. The earth being spherical , its surface is curved , and every line traced accurately on the surface , is also curved . 66. If large portions of the earth's surface are to be measured , such as states and territories , its ...
Página 71
... paper can then be placed under them : then , by turning the screws back again the plates are drawn down and the paper held tightly . Fig . 1 represents the table with the paper partly put upon it : one edge of the paper has been placed ...
... paper can then be placed under them : then , by turning the screws back again the plates are drawn down and the paper held tightly . Fig . 1 represents the table with the paper partly put upon it : one edge of the paper has been placed ...
Página 72
... paper lies on the same side of the base with the objects . Then , tighten the clamp screw , and mark with a pin the point of the paper directly over the station , which point is determined most accurately by suspending a plumb from the ...
... paper lies on the same side of the base with the objects . Then , tighten the clamp screw , and mark with a pin the point of the paper directly over the station , which point is determined most accurately by suspending a plumb from the ...
Página 73
... paper . — When one paper is filled , and there is yet more work to be done , let the paper be removed and a second paper put on the table ; after which , the table may be used as before . Now , in order that the two papers may be put ...
... paper . — When one paper is filled , and there is yet more work to be done , let the paper be removed and a second paper put on the table ; after which , the table may be used as before . Now , in order that the two papers may be put ...
Página 75
... paper , of its bounding or other principal lines or such a representation of it , that all the lines and angles drawn on the paper have the same mutual relation as their corresponding lines and angles on the ground . In making such ...
... paper , of its bounding or other principal lines or such a representation of it , that all the lines and angles drawn on the paper have the same mutual relation as their corresponding lines and angles on the ground . In making such ...
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Página 57 - Being on a horizontal plane, and wanting to ascertain the height of a tower, standing on the top of an inaccessible hill, there were measured, the angle of elevation of the top of the hill 40°, and of the top of the tower 51° ; then measuring in a direct line 180 feet farther from the hill, the angle of elevation of the top of the tower Cway 33° 45' ; required the height of the tower.
Página 15 - FRACTION is a negative number, and is one more than the number of ciphers between the decimal point and the first significant Jigure.
Página 15 - The characteristic of a number less than 1 is found by subtracting from 9 the number of ciphers between the decimal point and the first significant digit, and writing — 10 after the result.
Página 102 - The line so determined makes, with the true meridian, an angle equal to the azimuth of the pole star; and from this line the variation of the needle is readily determined, even without tracing the true meridian on the ground. Place the compass upon this line, turn the sights in the direction of It, and note the angle shown by the needle. Now, if the elongation at the time of observation...
Página 21 - The circumference of every circle is supposed to be divided into 360 equal parts called degrees, each degree into 60 equal parts called minutes, each minute into 60 equal parts called seconds.
Página 97 - But the star being at a distance from the pole equal to 1° 30' nearly. It performs a revolution about the pole in a circle, the polar distance of which is 1° 30': the time of revolution is 23 h. and 56 min. To the eye of an observer this star is continually in motion, and is due north but twice in 23 h. 56 min.; and is then said to be on the meridian. Now, when It departs from the meridian it apparently moves east or west for 5 h.
Página 100 - ... three inches square, be nailed to the lower edge of it, for the purpose of holding a candle. About twenty-five minutes before the time of the greatest eastern or western elongation of the pole-star, as shown by the tables of elongations, let the theodolite be placed at a convenient point and leveled. Let the board be placed about one foot in front of the theodolite, a lamp or candle placed on the shelf at its lower edge; and let the board be slipped up or down, until the pole-star can be seen...
Página 2 - An Act for the Encouragement of Learning, by securing the copies of Maps, Charts, and Books, to the authors and proprietors of such copies during the time* therein mentioned," and extending the benefits thereof to the arts of designing, engraving, and etching historical and other prints.
Página 100 - Let the board be placed about one foot in front of the theodolite, a lamp or candle placed on the shelf at its lower edge ; and let the board be slipped up or down, until the pole-star can be seen through the hole. The light reflected from the paper will show the cross hairs in the telescope of the theodolite. Then, let the vertical spider's line be brought exactly upon the pole-star, and, if it is an eastern elongation that is to be observed, and the star has not yet reached the most easterly point,...
Página 100 - ... to coincide with the vertical hair. Then mark the point directly under the theodolite; the line passing through this point and the staff makes an angle with the true meridian equal to the azimuth of the pole-star. From the table of azimuths, take the azimuth corresponding to the year and nearest latitude. If the observed elongation was east, the true meridian lies on the west of the line which has been found, and makes with it an angle equal to the azimuth. If the elongation was west, the true...