Elements of Surveying, and Navigation: With Descriptions of the Instruments and the Necessary Tables |
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Page 58
... observation . Hence , the height of the instrument is to be added , in order to obtain the true result . SECOND METHOD . 38. When the nature of the ground will admit of it , measure a base line AB in the direction of the object D. Then ...
... observation . Hence , the height of the instrument is to be added , in order to obtain the true result . SECOND METHOD . 38. When the nature of the ground will admit of it , measure a base line AB in the direction of the object D. Then ...
Page 79
... observation . 26. Having determined the index error , let the axis of the telescope be directed to any point either above or be low the plane of the limb , and read the arc indicated by the 0 of the vernier . To the arc so read apply ...
... observation . 26. Having determined the index error , let the axis of the telescope be directed to any point either above or be low the plane of the limb , and read the arc indicated by the 0 of the vernier . To the arc so read apply ...
Page 85
... observed ( Bk . II . , Sec . I. , Art . 16 ) , that Gunter's chain of four rods or 66 feet in length , and use among surveyors . In measuring land , the length. which is divided into 100 links , is the chain in general SEC . IL ] 85 AREA ...
... observed ( Bk . II . , Sec . I. , Art . 16 ) , that Gunter's chain of four rods or 66 feet in length , and use among surveyors . In measuring land , the length. which is divided into 100 links , is the chain in general SEC . IL ] 85 AREA ...
Page 103
... observations : 2d . Local attractions , or the derange- ment which the needle experiences when brought into the vicinity of iron - ore beds , or any ferruginous substances . To guard against these sources of error , the reverse bearing ...
... observations : 2d . Local attractions , or the derange- ment which the needle experiences when brought into the vicinity of iron - ore beds , or any ferruginous substances . To guard against these sources of error , the reverse bearing ...
Page 110
... observed ( Art . 18 ) , that if the measurements on the field be correctly made , the sums of the northings and southings will be equal to each other , as also those of the eastings and westings . It is the opinion of some surveyors ...
... observed ( Art . 18 ) , that if the measurements on the field be correctly made , the sums of the northings and southings will be equal to each other , as also those of the eastings and westings . It is the opinion of some surveyors ...
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Common terms and phrases
axis back-sight base line called centre column comp cosine Cotang course degrees determined difference of level direction divided double meridian distance draw east error example feet figure fore-sight given angle given line given point ground Gunter's chain half hence horizontal angle horizontal distance horizontal line horizontal plane hypothenuse inch instrument intersection latitude and departure length line of collimation logarithm marked measure method miles multiplied natural sines needle parallel parallelogram passing perpendicular plane of reference Plane Sail plane triangle plot protractor quotient radius right angles right-angled triangle rods scale of equal screws secant sector sides sights similar triangles spherical excess spider's lines square chains staff station straight line subtract surface survey Tang tangent theodolite trigonometrical variation vernier plate vertical limb yards
Popular passages
Page 12 - The logarithm of . the quotient of two numbers, is equal to the logarithm of the dividend diminished by the logarithm of the divisor.
Page 40 - The circumference of every circle is supposed to be divided into 360 equal parts, called degrees...
Page 47 - C' (89) (90) (91) (92) (93) 112. In any plane triangle, the sum of any two sides is to their difference as the tangent of half the sum of the opposite angles is to the tangent of half their difference.
Page 140 - ... 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. and 59 min., and then returns to the meridian again. When at its greatest distance from the meridian, east or west, it is said to be at its greatest eastern or western elongation.
Page 63 - 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.
Page 11 - THE LOGARITHM: of a number is the exponent of the power to which it is necessary to raise a fixed number, to produce the given number.
Page 144 - Now, if the elongation, at the time of observation, was west, and the north end of the needle is on the west side of the line, the azimuth, plus the angle shown by the needle, is the true variation. But should the north end of the needle be found on the east side of the line, the elongation being west, the difference between the azimuth and the angle would show the variation, and the reverse when the elongation is east. 1. Elongation west, azimuth 2° 04' North end of the needle on the west, angle...
Page 41 - The secant of an arc is the line drawn from the centre of the circle through one extremity of the arc, and limited by the tangent passing through the other extremity. Thus, 00 is the secant of the arc AB.
Page 46 - CB : CA : : sin A : sin B. For, with A as a centre, and AD equal to the less side...
Page 24 - In a Right-angled Triangle, the side opposite the right angle is called the Hypothenuse ; and the other two sides are called the Legs, and sometimes the Base and Perpendicular.