Elements of Surveying: With the Necessary TablesJ. & J. Harper, 1830 - 306 páginas |
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Página 44
... line of collimation . - Turn the vernier plate , till the telescope comes directly over two of the levelling screws , between the plates DE and FG . Turn these screws contrary ways , keeping them firm against the plate FG , till the ...
... line of collimation . - Turn the vernier plate , till the telescope comes directly over two of the levelling screws , between the plates DE and FG . Turn these screws contrary ways , keeping them firm against the plate FG , till the ...
Página 78
... line , AD , ( Pl . 5 , Fig . 3 , ) equal in length to , } , } , or 1 inch , or of any other convenient dimension ... FG . It follows from the proportion of similar triangles , that the part of the line .01 , intercepted between the lines ...
... line , AD , ( Pl . 5 , Fig . 3 , ) equal in length to , } , } , or 1 inch , or of any other convenient dimension ... FG . It follows from the proportion of similar triangles , that the part of the line .01 , intercepted between the lines ...
Página 83
... FG were a line measured , NFS the meridian , and SFG the bearing , or course ; then FGʻ would be the southing , or difference of latitude , and GGʻ the departure east . It is evident that the distance run , the difference of latitude ...
... FG were a line measured , NFS the meridian , and SFG the bearing , or course ; then FGʻ would be the southing , or difference of latitude , and GGʻ the departure east . It is evident that the distance run , the difference of latitude ...
Página 92
... line . First , with a protractor , or scale of chords , make the angle SFG equal to 16 ' , and lay off , from a convenient scale of equal parts , the line FGʻ , equal to 3.50 , its length , taken from the column of distances . Or ...
... line . First , with a protractor , or scale of chords , make the angle SFG equal to 16 ' , and lay off , from a convenient scale of equal parts , the line FGʻ , equal to 3.50 , its length , taken from the column of distances . Or ...
Página 109
... line corresponding to FB ; then sight to the points G and H , and draw the lines FG and FH Take the distance FB , equal to 265 feet , from a scale of equal parts , and apply it to the corresponding line on the paper ; this determines ...
... line corresponding to FB ; then sight to the points G and H , and draw the lines FG and FH Take the distance FB , equal to 265 feet , from a scale of equal parts , and apply it to the corresponding line on the paper ; this determines ...
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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...