Practical Military Surveying and Sketching: With the Use of the Compass and Sextant, Theodolite, Mountain Barometer, Etc. ... |
Other editions - View all
Common terms and phrases
accuracy adjustment angle of elevation angular distance Arcturus artificial horizon barometer base line centre chain circle clamping coincide compass contours correction cosec declination determine the position difference direction distance A B east equator error feet graduated arc Greenwich Greenwich mean ground Gunter's chain height hills horizon-glass horizontal distance horizontal plates index-arm index-error instrument intersection latitude length limb longitude lower magnetic marked means merid meridian altitude method miles military sketch minutes moved Nautical Almanac observed angles obtain opposite bearing paces paper parallax parallel plotted pole star portion practice protractor refraction represent right angle road scale selected semi-diameter sextant side sight-vane sine slope station subtract sun crossed sun's Suppose survey take the bearing taken taking angles tance tangent telescope theodolite tion triangle true altitude upper vertical arc vertical distance whilst zenith distance zero دو
Popular passages
Page 119 - TO THEIR DIFFERENCE ; So IS THE TANGENT OF HALF THE SUM OF THE OPPOSITE ANGLES ; TO THE TANGENT OF HALF THEIR DIFFERENCE.
Page 168 - ... to the tangent of the angle adjacent to the first side. CASE 3. — When the three sides are given. RULE 6. To find an angle. Subtract the sum of the logarithms of the sides which contain the required angle, from 20; to the remainder add the logarithm of half the sum of the three sides, and that of the difference between this half sum and the side opposite to the required angle. Half the sum of these three logarithms will be the logarithmic cosine of half the required angle. The other angles...
Page 156 - Then, if the zenith distance and declination be both north or both south, add them together; but if one be north and the other south, subtract the less from the greater, and the sum or difference will be the latitude, of the same name with the greater.* EXAMPLE I.
Page 41 - Sextant. the observed object be distant fully half a mile, then the instrument is in adjustment, and is ready for use, but if the two zero points do not agree, the index-arm is moved until they do, and the key is then placed in one of the key-holes, and the reflected image of the distant object is made to coincide with the object seen direct through the lower part of the horizon - glass.
Page 140 - In thai case, having found the difference as above, add ^^5 of the result for each degree by which the mean temperature of the air at the two stands exceeds 55°; subtract the like proportion if the mean temperature be below 55°. When the upper thermometer reads highest, for "subtract" say "add," and vice versa in the foregoing rule.
Page 156 - OOP, will give the zenith distance; to be called North or South, according as the observer is north or south of the star at the time of observation.
Page 81 - Angle from any point on the ground by means of a Hope. To set off from any point A, a line at right angles to a given direction, as AE, measure an equal distance on each side of A, in the same straight line as AE, this equal distance being about one-fourth of the length of the rope. Let C and D be these points. Fasten the ends of the rope at...
Page 166 - The moon's position could be fixed by measuring the angular distance between the moon and the sun or one of the four...
Page 139 - B, add the log. of the height of the barometer at the upper station, and subtract their sum from the log. of the height of the barometer at the lower station, and call the remainder R ; then take out the log. of R, and add it to the numbers A and C, and the sum, rejecting tens from the index, will be the log. of the difference of the altitudes of the two stations in feet.
Page 163 - Thus we have upper limb 0, lower limb 0, right limb 0 left limb 0. Longitude. — The spherical angle at the pole between the meridian of Greenwich and the meridian of any place on the earth's surface is the longitude of that place. Longitude may be measured in degrees of arc on the equator or on any parallel of latitude. Local Mean Time. — The time used in everyday life, and is the same as civil time. It is measured by the length of the mean solar day divided into...