Surveying instrument

“ Thus, the need for practical mathematical instruments for the surveyor and navigator became critical in proportion to the need for men to make and use them, and it is not surprising to discover that the majority of the instruments produced and advertised by early American makers were for surveying, with nautical instruments in second place. Generally, the surveyors were not professionals; they were farmers, tradesmen, or craftsmen with a sound knowledge of basic arithmetic and occasionally with some advanced study of the subject as taught in the evening schools. ”

“ All the apparatus described are, when necessary, shown in illustrations. The instruments used by surveyors are described in the first part, the first six chapters being devoted to instruments for measuring distances, instruments for determining directions, instruments for determining horizontal lines, instruments for measuring angles, the planetable, and additional instruments used in surveying and plotting. ”

“ The simple work includes that which can be carried on with a few cheap instruments easily secured or made by the boys. The advanced work requires better instruments and is adapted to high school boys. Only the simple work will be described.
Home-made
The instruments needed in simple surveying are, compass, measuring tape, draughtsman's scale, protractor, drawing materials and a small home-made transit. The leader should, if possible, become familiar with some good textbook on surveying, such as Wentworth's Plane Trigonometry and Surveying. ”

“ At the other extreme comes the modified running survey, which in point of practical accuracy falls little short of that attained by irregular triangulation. Some of these modifications will be briefly noticed. A running survey of a coast-line between two harbours, that have been surveyed independently and astronomically fixed, may often be carried out by fixing the ship on the points already laid down on the harbour surveys and shooting up prominent intermediate natural objects, assisted possibly by theodolite lines from the shore stations. ”

“ When the scale of a survey is large, the linear and angular measures are usually recorded on the spot in a field- book and afterwards plotted in office; when small they are sometimes drawn on the spot on a plane table and the field-book is dispensed with. ”

“ Surveying and map making have always been two of the most interesting things a civil engineer has had to do. And, like George Washington, many of the men we look up to today as successes in different lines worked as surveyors in their younger days. Surveying takes one out of doors, and is apt to lead him into the unknown and unexplored byways of the earth.
Though modern surveyors often use precise and expensive instruments, creditable surveys can be made with simple and inexpensive apparatus. ”

“ But the method to which the term " levelling " is always applied is that of the direct determination of the differences of height from the readings of the lines at which graduated staves, held vertically over the points, are cut by the horizontal plane which passes through the eye of the observer. Each method has its own advantages. The former is less accurate,, but best suited for the requirements of a general geographical survey, to obtain the heights of all the more prominent objects on the surface of the ground, whether accessible or not. ”

“ In a detailed survey the coast is sketched in by walking along it, fixing by theodolite or sextant angles, and plotting by tracing- paper or station-pointer. A sufficient number of fixed marks along the shore afford a constant check lining, on the minor coast-line stations, which should be plotted on, or checked by, lines from one to the other wherever possible to do so. When impracticable to fix in the ordinary way, the ten-foot pole may be used to traverse from one fixed point to another. ”

“ The measured base for an extended survey is provisional only, the scale resting ultimately mainly upon the astronomical positions observed at its extremes. In the case of a plan the base is absolute. The main triangulation, of which the first triangle contains the measured base as its known side, establishes a series of points known as main stations, from which and to which angles are taken to fix other stations. A sufficiency of secondary stations and marks enables the detail of the chart to be filled in between them. ”

“ The classwork covers a thorough drill in the principles of hydrographic and geodetic surveying and spherical trigonometry and practical astronomy. This is supplemented by fieldwork covering the use of the stadia, plane table and traverse board in the execution of topographic and engineering surveys, the methods of gaging streams, the geodetic and astronomic work necessary for control surveys, and the execution of preliminary and location route surveys for highways and sewers which are used in the design work of the courses in Highways and Sanitation. ”

“ The method of surveying varies with the magnitude of the survey, which may embrace an empire or represent a small plot of land. All surveys rest primarily on linear measurements for the direct determination of distances; but linear measurement is often supplemented by angular measurement which enables distances to be determined by principles of geometry over areas which cannot be conveniently measured directly, such, for instance, as hilly or broken ground. ”

“ I had two complete sets of instruments for astronomical observations and for use in surveying. One set had been given to me by the Royal Geographical Society of London. The other was my own. Each set consisted of the following instruments. A six-inch sextant. The hypsometrical apparatus, a device used for measuring heights by means of boiling-point thermometers, which had been specially constructed for work at great elevations. ”

“ When a surveyor desires to ascertain the distance of a visible object which he cannot approach, he must avail himself of the same principle of nature. He measures off on the ground where he is a suitable baseline, and takes the angle of the object from each end of it, not vaguely by his unaided eyesight alone, but with a well-graduated instrument. ”

“ Louis, Missouri—are of special interest even to practiced surveyors, as they treat of special branches of surveying, about which little, if any, mention is ever made in books for the use of students.
What may be called the scientific part of surveying—geodetic surveying—is fully treated and made comprehensible to those whose purpose is not to devote themselves to geodetical work exclusively, but who have, all the same, to be familiar with the scopes and purposes of geodetical measurements, as every engineer and surveyor has to be. ”

“ A chart depends on the surveys that furnished its data, and its accuracy and reliability rests upon that survey. Even with the most careful surveys, where the lead is used to ascertain depths, there are many instances where pinnacle rocks have escaped detection by coming between the casts of the lead taken by the surveying party. These isolated rocks become points of great danger to vessels of deep draft, and it becomes a measure of safety to avoid rocky coasts and offshore patches by giving them a wide berth. ”

“ Consequently, when the vernier is set to the mercurial column, the difference shown by the vernier from the tenth on the scale is the hundredths to be added to the inches and tenths of the scale.
A little practice will accustom a person to set and read any barometer quickly; an important matter where accuracy is required, as the heat of the body, or the hand, is very rapidly communicated to the instrument, and may vitiate, to some extent, the observation. ”

“ The Professors of this Science [of land surveying] are honoured with a more earnest attention than falls to the lot of any other philosophers. Arithmetic, Theoretical Geometry, Astronomy, and Music are discoursed upon to listless audiences, sometimes to empty benches. But the land surveyor is like a judge; the deserted fields become his forum, crowded with eager spectators. You would fancy him a madman when you see him walking along the most devious paths. ”

“ A geographical survey must equally start from a base and be supported by triangulation, or at least by some process analogous $**„%** of to triangulation, which will furnish the necessary skeleton on which to adjust the topography so as to ensure a complete and homogeneous map. ”

“ In 1498 Vasco da Gama saw a chart of the coast-line of India, which was shown him by a Gujarati, and there can be little doubt that he benefited largely by information obtained from charts which were of the nature of practical coast surveys. The beginning of land surveying (apart from small plan-making) was probably coincident with the earliest attempts to discover the size and figure of the earth by means of exact measurements, i.e. with the inauguration of geodesy (see Geodesy and Earth, Figure of the) , which is the fundamental basis of all scientific surveying. ”

“ When a hill peak or other prominent object has been observed from a number of stations whose co-ordinates are already fixed, the converging rays may be projected graphically, and from an examination of their several intersections the most probable position of the object may be obtained almost as accurately as by calculations by the method of least squares, which are very laborious and out of place for the deter- mination of a secondary point. The following is a description of the application of this method to points on a plane surface in the calculations of the ordnance survey. ”

“ Pierce showed that the necessities of the Coast Survey extended its operations to all parts of the United States. No science could be divided and separated so as to stand alone. If one begins by measuring his town-lots, the method involves geometry and astronomy, geology and surveying, including ultimately the coast survey. ”

“ The survey industry that do not renew the registration certificate will be deemed as the survey industry of which the businesses are terminated. Article 41 The results of the consigned surveying and mapping tasks should be audited by professional survey engineers according to the audit regulations. The type of applicable certification, the implementation scope, certification items and rules concerning other required documents should be decided upon by the central authority concerned with the supervising authority of the Professional Engineers Act. ”

“ It is particularly suitable in areas of complex hydrography containing numerous rocks, shoals, and obstructions dangerous to survey vessels. The technology has developed and matured since the 1970’s, and in some areas of the world up to 50% of the hydrographic surveying is done with lasers. Survey rates of some 65 square km per hour are possible, at about a quarter of the cost of comparable vessel surveys. Data density is variable, ranging down to some 1-2 meters square, and depths from one half to over 70 meters have been successfully surveyed. ”

“ If, from too great depression of the lower parts of the field, or too great distances for observation, it becomes necessary to take up a new position with the instrument, the new level should be connected, by measurement, with [pg 107] the old one, and the new observations should be computed to the original plane. ”

“ Within the area surveyed by traverse nearly every mile of road has been run. With the exception of those in the cities, nearly every house and every church in the commonwealth has been located, either by intersection with the plane table or by traverse.
The organization of the surveying parties has been of the simplest character. Plane table work has been carried on by one man with an assistant, the latter doing little more than attend the plane tabler and assist him in carrying the instruments. ”

“ Surveying and levelling will also form an important part of his duties. In order to understand them it is necessary that he should know thoroughly plane and spherical trigonometry, and the calculations necessarily connected with them. He should also have a certain knowledge of astronomy, to enable him to calculate the tides and other phenomena connected therewith, and to be able to lay down correct charts of any harbour or sea coast, with the soundings, currents, and winds prevailing there. ”

“ Traversing and Fiscal, or Revenue, Surveys Traversing is a combination of linear and angular measures in equal proportions; the surveyor proceeds from point to point, measuring the lines between them and at each point the angle between the back and forward lines; he runs his lines as much as possible over level and open ground, avoiding obstacles by work- ing round them. ”

“ On large scale surveys whitewash marks or flags should mark the ends of the lines, and for the back transit marks natural objects may perhaps be picked up; if not, they must be placed in the required positions. The boat is fixed by two angles, with an occasional third angle as a check; the distance between the fixes is dependent upon the scale of the chart and the rapidity with which the depth alters; the 3, 5 and 10 fathom lines should always be fixed, allowing roughly for the tidal reduction. The nature of the bottom must be taken every few casts and recorded. ”

“ The surveying of the public lands may be thought by many to be light, easy work, but it is really hard and rough. The surveyors are subjected to much exposure, especially in the winter or rainy season. ”