Field Engineers Bulletin

No. 8 FIELD ENGINEERS BULLETIN U.S. COAST & GEODETIC SURVEY DECEMBER 1934 INDEX DECEMBER 1934 BULLETIN NO.8 THE MATCHLESS (Frontispiece) Page Editorial 1 Rodman's Reverie R.S.Clark 2 Calibration of Taut Wire Apparatus Ship OCEANOGRAPHER E. A. Seran 3 Long Line Triangulation in Alaska, 1953 A. M. Sobieralski 8 The Dorsey Fathometer 12 History of the Local Control Surveys Project H. W. Hemple 16 The Foucault Pendulum Experiment T. C. Lyon 20 Impressions of a Mathematician in the Field H. P. Kaufman 23 Map of the Philippine Islands 24 Rapid Observing 25 Appreciation (Letter from Captain P. A. Murchie) 26 New Form of Chiseling ? 26 Projects, Various Divisions 27 Progress Sketches and Distribution of Parties 1933-34 30 Types of Water Signals W. E. Parker 50 Framing of Wooden Scaffolds C. A. Egner 52 Wooden Towers for Triangulation E. R. McCarthy 56 Recent Acoustic Work of the U.S. Coast and Geodetic Survey P. A. Smith 60 Submarine Valley off Chesapeake Bay Entrance 76 National Resources William Bowie 77 Changes in Shore-line Coast of Louisiana T. B. Reed 78 Visit to Massachusetts Institute of Technology Surveying Camp N. H. Heck 79 Page Disturbance by Earthquake While Observing W. W. Kessler 80 Increased Accuracy of Topographic Positions on Aluminum Mounted Sheets 81 Life on a Survey Ship from Empire Survey Review 82 The Cheltenham Magnetic Observatory 83 The ABC of Triangulation Adjustment H. P. Kaufman 88 Contrast between Adequate and Inadequate Surveys 105 Organization of Parties (Charts) 106 The Problem of Reconnaissance William Mussetter 110 Triangles Again A. A. Lockerbie 112 The Transparent Diagonal Scale A. A. Lockerbie 113 The Operation of a Large Steel Tower Triangulation Party C. I. Aslakson 115 Lessons of the Expanded Photo Mapping Work of the Coast and Geodetic Survey, in Relation to Plans for Accelerated Mapping. O. S. Reading 118 Precast Post Lifter A. C. Thorson 120 Registering Sounding Sheaves 121 Applications for Membership, A.S.C.E. 124 American Society of Photogrammetry 125 The Coast Survey on the Pacific Coast T. J. Maher 126 Bomb Returns, Radio Acoustic Ranging H. Odessy 136 Report of Assistance Rendered A. M. Sobieralski 137 Records for Fourth Order Control Stations 137 Signal Reminder, International Code 138 A Fifty Inch Precision Camera O. S. Reading 140 1 EDITORIAL A New Deal for Surveying and Mapping Although the subject of mapping was not specifically mentioned in President Roosevelt's recent message to the 74th Congress, it requires but little imagination to see that one of the first requirements for carrying out effectively his vast and far-reaching public works program will be a provision for accurate, basic maps of the entire United States. Dependable maps are essential to the successful accomplishment of the majority of projects proposed to be undertaken. Soil erosion, reforesta- tion, flood control, power and irrigation projects cannot be planned in- telligently without them. That the United States has never had a coordinated mapping policy is unfortunate. The result is that it now finds itself woefully behind the leading nations in respect to basic maps. However, definite advances have been made in recent years. Due to generous allotments from the Public Works Administration, surveying and mapping have assumed more nearly the positions they should have occupied years ago. The results of the last two years alone have had a pronounced effect in educating the public to an appreciation of the value of good maps, and there is every reason to hope that a sound national mapping policy will be adopted. Don't Cut the Comers When one looks back over the century and more of accomplishment of the United States Coast and Geodetic Survey, he is particularly impressed with the foresight which inspired the accuracy that was built into the first surveys. It is most significant that they have stood the test of time and the economic advancement of our Nation through the years. The past several years have seen a growth in surveying activity never before equalled. In this rapid growth there have been times when the maintenance of the standards of accuracy established by long exper- ience in this Bureau has been difficult. It is well in such times to think of the beginning of our first order surveys, over a hundred years ago, and to wonder where we would be now if the first surveys had been made only with such accuracy as was satisfactory at the time. We have discovered many improvements in methods, instruments, and economies in surveying, but it should never be said that these improvements in pro- duction have been made at the sacrifice of the original standards. Now, more than ever we should be looking for methods that will lead to greater accuracy and fidelity of results. There was a period when we considered the third-order accuracy of our coastal triangulation more than adequate to control the detailed surveys of the coasts and contiguous waterways. Only recently have we completed the first order work that ties many of these previous surveys together, and exposes the short-comings of many of them. Time has justi- fied the surveys which occasionally were criticized in some quarters as "too accurate"; on the other hand, there has never been a case, when under some special pressure we lowered our usual standards, that sooner or later we did not regret it. Our good name has always stood for accuracy among the engineers of both the nation and the world. May we perpetuate this enviable reputation. 2 RODMAN'S REVERIE R. S. Clark When Life's last traverse is finished And the notes are computed and checked, When angles and levels and chainage Are purged of the last defect, We shall turn in the tools and the notebooks And stamp off the ice and the snow And take us a good long noon hour Of a thousand years or so. Then, when we are all quite rested, The Chief will announce a plan For a Galaxydetic survey job With a trillion miles to span. Out past the far horizons, Out past the Pleiades, To tie in the solar system With the neighboring galaxies. All distances chained precisely With an invar light-year chain. All levels referred to datum Of the true ecliptic plane In twenty decimal places, Or possibly twenty-one, With never a doubtful reading, And never a line re-run. All angles to accurate fractions Of a pip on the Zodiac; Doubled and thrice redoubled; Repeated forward and back. Horizons exactly closing, All pink and purple and gold, Where instruments read to millionths And fingers are never cold. Then rodmen will not be footmen, Pacing a weary route, But will ride two weeks in a rocket ship To set the front target out. The chain gang will not inch along With bucks and tension bars, But will shoot by stadia just like that, From here to the horns of Mars! And, 'ere we have measured and plotted The infinite boundaries of Space, The rumbling March of the Alphabet Shall have passed the decimal place, And each in his separate station Shall labor as best he can For the profit of all creation And the good of the General Plan. (Mr. Clark is employed on the Local Survey Project in Michigan). 3 CALIBRATION OF TAUT WIRE APPARATUS U. S. C. & G. S. SHIP OCEANOGRAPHER H. A. Seran, H. & G. Engineer, U. S. C. & G. Survey, Comd'g. (The remarkable consistency of twenty observations made to obtain the apparent velocity of sound in shoal water off the coast of Maryland during the spring of 1933, (see Field Engineers Bulletin No. 7, p. 115) sug- gested that the limits of the accuracy obtainable with the taut wire apparatus might be increased, and that the calibration used, namely, a direct measurement of the sheave circumference, was open to criticism in that it did not represent the actual conditions encountered during use. Such errors as would result from steering of the vessel, temperature changes in the wire from the time it leaves the sheave until it reaches the bottom, and the possibility of dragging of the wire anchor, all might affect the value of a single revolution as obtained from actual runs, and so give quite a different factor for the sheave than obtained by direct measurement of the circumference. The report below describes the method used in comparing the two measurements, and this work should be considered from two view points: the accuracy with which measurements can be made with the taut wire apparatus in shoal water and uniform sea bottom, and the coordination of observations as practiced in hydrographic work. It is also something of a criterion of the accuracy with which two observers can determine the position of a moving vessel by observations on shore objects from the ship.) (Editor) Instructions Under date of May 1, 1934, instructions for the calibration of the taut wire apparatus installed on board the Ship OCEANOGRAPHER were issued as follows: "As soon as practicable you will please test the previous calibration of your taut wire apparatus by a measurement of the distance between two points, the positions of which are determined by sextant observations on triangulation signals, using a third angle for checking purposes, and com- puting the distances between positions. The calibration run should not be less than three miles in length. It should be made over uniform bottom and far enough off shore to permit using the same fix at each end of the line. A third position should be determined about midway along the line as a check. Temperatures of both the air and the bottom, should be taken near the ends of the line, at the time of the calibration.

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