Show SHOR SHOUT T AND METHODS IN SURVEYING G PRACTICE 11 MINES AND MINERALS SCRANTON PA of lei of of lei WI IVI WI of Is lei 14 1011 there are many short methods in the practice of surveying known to the engineer that enable him at times to make long strides toward the completion of his work in the use of these short cuts the necessary observations are taken by the engineer or without the aid of and unbeknown to his assistants so that his announcement no to them upon their arrival at an stream or an insurmountable precipice or other impassable obstruction that the work is completed beyond such a point sounds more as a fairy tale than a simple practical fact that permits them to A drw lad 1120 L jim jr ja a b flo 1 transfer their base of operations thither without the anticipated laborious toil common to suji obstructions this applies to all work of measurement or location not requiring side notes or profile elevations the writer has often in the surveying of townships sections land mining claims etc very materially shortened the work b by y taking observations or sights to certain prominent points thereby locating such points or connecting the same with the survey and making it possible to transfer operations to any one of them in surveying the land lines or boundary lines of any tract or mining claim the prominent features can genera generally liy be located by ob observations ions taken in this manner from different stations or points in the survey this method saves the labor of running special lines and taking the necessary measure measurements ments to locate such points or objects by taking such observations ions carefully to the hoisting rope for example of a shaft in the survey of a small mine the writer has often made connection and carried the surface survey into the mine without apparently approaching approach int g the shaft not infrequently causing the surprise of the onlooker or helper and eliciting the question how do you establish your connections success in surveying depends to a larger extent than is often recognized by the engineer or surveyor upon just such timesaving saving methods as this we have seen en would scoff coff at such in methods as being inaccurate but who ha are themselves so careless in the matter of measuring with the chain or tape or in observing and reading I 1 an an angle gle with the instrument that their work is wholly unreliable and productive of no absolute results the successful engineer possesses an advantage over his competitor by knowing where accuracy is needed with this man it is an unvarying rule that accuracy acy begins in the careful and uniform handling of the instrument and measuring line it is useless to split hairs over tack points when the chain is two tenths long ion or short and needs correction or the instrument ment out of adjustment irmay it may seem a strong statement but it is nevertheless a fact that many engineers cannot measure 1000 feet in a direct line upon level ground and then measure back upon the same line and tally on the starting point many do not know th atthe ordinary engineers steel tape is graduated under a tension or pull of ten pounds and that a difference of ten pounds in the pull exerted upon the tape or a difference of 31 degrees F in temperature will either of them produce a variation of one fourth inch per hundred feet of length in the meas aring line in spite of ignoring these corrections ions we find men measuring and sighting with the most careful scrutiny to plumb line and tack points and consuming hours upon a sabbath or rest day in vainly trying to plumb a shaft the point we wish to emphasize here is that much time is to be saved by the various expedients adopted by the in charge of the survey we will mention a few of these points passing obstacles when a line of survey runs through a house or barn or crosses a timber patch marsh or other piece of ground that it is desirable to avoid P 7 4 wa aa 2 the engineer or surveyor often squares off and runs upon an offset line parallel to t tho he line of survey and at such a distance from it that the obstruction is avoided the method of squaring off is illustrated at a fig 1 and will be readily understood this method requires turning off four bour angles two to the right and two to the left itis it is 0 often preferable to adopt one of the methods shown at b or c either of these methods requiring the turning off of only three angles the method shown at b requires no calculation since the deflected line avoiding the obstruction form two sides of an equilateral triangle and the intercepted portion of the survey line A B is therefore equal to the length of either of the deflected lines run to avoid the obstruction at c the intercepted portion of the survey line A B is double the length of the shorter one of the two deflected lines in this method the first angle deflected may liay be y 3 aa MIRML t ct ta a FIG 3 either 60 degrees or 30 degrees but in elther either case the longer of the two deflected lines must be 1732 times the shorter it is evident that any other angles may be used in avoiding obstructions but always the sum of the angles turned to the right must be equal to the sum of the angles turned to the left and it is more convenient to use such angles as 30 degrees and go 60 degrees or 60 degrees and 60 degrees or 45 degrees and 45 degrees in the latter case which we have not illustrated the deflecting lines will form the two equal sides of an isosceles triangle the of this triangle is the intercepted portion of the survey line and is always 1414 times the length of either of the deflected lines triangulation we do not refer here to such tr as requires an independent base line we assume the th e method of triangulation is understood and only wish to draw attention to the fact that time and labor may often be saved loy dy taking observations from any two stations of the survey from which some desired point can be seen it is not necessary that such point be in the boundary line of the survey it may be situated near such boundary or corner this is illustrated in fig 2 a and b in the former by observing the point c from any two convenient stations of the survey its position is determined and it will not then be necessary to carry the survey from station b to c through the dense timber and underbrush shown in the cut but having completed the survey to b me instrument can be mo moved ved to c e and taken to p or a or any other station from which c has been observed and the survey con tinned linued in like manner in b the point s at the top of a precipitous bluff is observed from the stations t and v upon the road in the valley A simple calculation will then determine the position of the point s and the survey can be continued by removing the instrument to that point the points c and s fig 2 may be located by sending a flagman forward or br a prominent feature of the landscape may be sighted as the lone pine upon the precipitous bluff shown in fig 3 or the church spire in fig 4 and these may be taken as reference points it is not necessary that such reference points be accessible ces sible for the setting up of the instrument over them in fig 3 the instrument is shown as having been carried forward and set up at 0 upon the line v s at any convenient distance from the pine tree or reference point this distance may be measured after the instrument is set up by measuring the did distance tance 0 s to the center of the pine tree or it may be ignored for the present and the length of the line v s corrected later by taking an observation from some point p upon the line 0 p again the reference point s may be such as to be wholly inaccessible as for ex example ampie the church spire shown in fig 4 in this case Y s being the inaccessible point under the spire of the church the instrument is carried forward and lined in at some point 0 on the line v x and the survey is then continued along the line 0 p the length of the line v x is corrected as before by an observation of the spire from some point p in all these figures the measured lines v t and 0 p of the survey are drawn full while the sight lines v s t s 0 s and p s are dotted it must not be supposed that this method r of surveying by means of inaccessible reference points possesse possesses pos any elements of inaccuracy it is on the contrary one of the most accurate methods of surveying that can be employed since the reference points are fixed and afford rigid permanent sights that can often be seen a long distance A triangulation from a carefully measured base line is susceptible of more accurate work by far than would result from chaining or measuring the same distance one of the most prolific sources of error in surveying practice is the inaccuracy due to chaining over bad country and the most serious hindrance to a survey arises when a line must be cut through umber timber and un 1 der growth hence any means for the avoidance of these difficulties will have time and ana labor 1 |