UNITED STATES DEPARTMENT OF THE INTERIOR Harold L. Ickes, Secretary GEOLOGICAL SURVEY W. C. Mendenhall, Director Bulletin 882 SPIRIT LEVELING IN MASSACHUSETTS 1922-35 J. G. STAACK Chief Topographic Engineer UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1937 For sale by the Superintendent of Documents, Washington, D. C. ------ Price 15 cents CONTENTS Introduction. _ _--__--_-_____..___________. History and cooperation________________ 1 Classification of leveling_________________ 2 Adjustments. _ ___________________________ 3 Benchmarks. _ ___________________________ 3 Preservation and restoration of benchmarks. 4 Datum__ -____-__--__-___-__-________. 5 Index map____________________________ 5 Personnel and equipment________________ 7 Third-order leveling._________________________ 9 Index_____________________________________ 153 ILLUSTRATIONS Page PLATE 1. Geological Survey benchmarks._____^..__.________________ 1 FIGURE 1. Index map of Massachusetts_______'_____________________ 6 2. Diagram of the Falmouth, Northampton, Plymouth, and Springfield quadrangles showing the smaller quadrangles into which they have been subdivided_________________ U. S. GEOLOGICAL SURVEY BULLETIN 882 PLATE 1 /y - -x<1 \ - <\<<::^ AN ^OM -^- * bEA rr, O 'O . C ^K '- ^LLA^ vx\^ ifiiMf. ^J, fi GEOLOGICAL SURVEY BENCHMARKS. A, Tablet used in cooperating States. The State name is inserted at G. B and D, Copper temporary benchmark, consisting of a nail and washer. A, C, and E, Tablets for stone or concrete structures. SPIRIT LEVELING IN MASSACHUSETTS, 1922-35 J. G. STAACK, Chief Topographic Engineer INTRODUCTION History and cooperation. Massachusetts had been entirely mapped by the United States Geological Survey in cooperation with the Commonwealth before 1896, the year in which the Geological Survey was first authorized to establish benchmarks. The cooperative topo­ graphic survey of the State was completed in 1887, but there is no record that any leveling was done as an aid to the mapping resulting from this survey. The recorded cooperative leveling in the State did not begin until 1922, and the present bulletin is the first to be published by the United States Geological Survey embodying the results of its leveling in Massachusetts. The contours shown on the quadrangle maps made before 1896 were of necessity based only upon the meager leveling control then available, supplemented by vertical angles. The earliest leveling before 1893 was done by State or municipal agencies and was purely local in scope. It was based upon various tidal datum planes for areas adjoining the coast and upon assumed datum planes for inland areas. In 1893, however, the State Topographic Commission undertook the task of providing reference heights for use both in reducing the main points of triangulation to a common geodetic surface and in the future revision of maps. For this purpose the commission engaged the services of C. H. Van Orden, of the United States Coast and Geodetic Survey, to extend a line of spirit leveling of high precision, based upon mean sea-level datum, along the Boston & Albany Railroad from Boston to Albany, there to connect with the precise leveling previously done by the Coast and Geodetic Survey along the Hudson River. This line was run by the double simultaneous method, using a Buff & Berger (cradle) precise level and one-piece rods treated with paraffin. The Van Orden line was apparently the first leveling of its character and scope attempted in Massachusetts by either a State or a Federal bureau. The results of this leveling were published in an appendix to the State Topographic Commission's report for 1893.1 ' See Commonwealth of Massachusetts, Report of the commissioners on the topographical survey for the year 1893, Boston, 1894. 1 2 SPIRIT LEVELING IN MASSACHUSETTS, 1922-35 In 1922, in cooperation with the War Department, the United States Geological Survey remapped the area within and adjacent to Camp Devens, near Ayer. Elevations to control the contouring of this area were determined by extending loops of third-order leveling (see p. 3), starting from previously established marks at Nashua, N. H., and including short local circuits in the Camp Devens area. Standard benchmarks were established along these lines of leveling, complying with the modern practice of third-order leveling. These local circuits have since been tied in by a line of levels run by the Commonwealth,' and the results adjusted accordingly. The United States Coast and Geodetic Survey began its first-order leveling in Massachusetts in 1923, when it extended a line northward across the State along the Connecticut River, another from Westerly, R. L, to Boston, and a third from Boston to Portland, Maine. In 1933 it reran the line from Springfield to Albany, N. Y., which formed part of the line originally run by the State Topographic Commission of 1893. The first-order level net thus established was further augmented by several hundred miles of first- and second-order leveling executed by engineers of the Massachusetts Department of Public Works, most of which was distributed through the eastern part of the State and all connected with the leveling done by the Coast and Geodetic Survey. Since October 1932 the United States Geological Survey has cooperated with the Commonwealth in a detailed remapping program, as a result of which lines of third-order leveling have been extended into quadrangles included in Barnstable, Bristol, Franklin, Hampden, Hampshire, Norfolk, Plymouth, Suffolk, and Worcester Counties. This program is still in progress. Benchmarks of the United States Coast and Geodetic Survey and the Massachusetts Department of Public Works were used as base points for third-order lines. The work was done in accordance with regulations prescribed for third-order leveling by the United States Geological Survey.2 Although, as previously stated, the third-order lines run by the United States Geological Survey in Massachusetts are tied to and based upon the first- and second-order lines run by the United States Coast and Geodetic Survey and the Massachusetts Department of Public Works, this bulletin includes the results of the work done by the Geological Survey only. Classification of leveling. Spirit leveling is classified according to the degree of refinement in the instruments and methods used and according to the closure errors. First-order leveling 3 consists of leveling done with the most improved instruments, all sections being leveled twice, in opposite » See Douglas, E. M., Leveling: U. S. Oeol. Survey Bull. 788; pp. 117-160,1918. See Avers, H. J., Manual of first-order leveling, U. S. Coast and Geodetic Survey Special Pub. 140, 1929. INTEODUCTION 6 directions, under varying conditions. Closures are not allowed to exceed the amount in feet represented by the formula 0.017y length of section in miles. All corrections for rod error, temperature, and unbalanced sights are applied, as well as the orthometric corrections for convergence toward the poles of level surfaces of different elevations. Second-order leveling, according to regulations of the United States Geological Survey, comprises lines leveled twice with reliable instru­ ments, though not necessarily of the most improved type. Closures are not allowed to exceed 0.035V length of section in miles. Third-order leveling is made up of lines that are run, either with first-order equipment or with an engineer's wye level and New York rods, in single-line circuits that are required to close within the limits, in feet, of 0.05 ^ length of circuit in miles. This is equivalent to 0.071 V length of section if the line is leveled twice. Adjustments. The adjustment of a leveling net begins with the first-order lines. Most of these lines in both the United States and Canada have already been combined in a general net, and the ortho- metric differences derived from the observed values by correction for the convergence of level planes toward the north have been adjusted to remove accidental closure errors by the mathematical method known as least squares. The Istfest adjustment of this kind was made in 1929 by the United States Coast and Geodetic Survey and is known as the "1929 general adjustment of first-order leveling." This adjustment included the first-order lines in Massachusetts, and the elevations thus derived are the fundamental references for elevations determined by second- and third-order nets. The third-order leveling of the United States Geological Survey in Massachusetts has been adjusted by determining weighted mean elevations for new junction points and prorating the errors of each link. The weights are taken as the reciprocals of lengths of links. The third-order net has thus been brought into agreement with the best information available for the results of the fundamental first-order leveling. Benchmarks. The standard benchmarks used by the United States Geological Survey in Massachusetts in 1922 are circular tablets 3% inches in diameter, with a thickness tapering from three-eighths of an inch at the center to about a quarter of an inch near the rounded edge. (See pi. 1.) Each tablet has a 3-inch shank attached to its under side at the center, by means of which it is cemented in place. The face of the tablet is cast with the words "U. S. Geological Survey", "In cooperation with the State of", "Elevation above sea feet", and "250 dollars fine for disturbing this mark." A cross inside a triangle at the center indicates the fiducial point for position or elevation. If the tablet is to mark a traverse station, the traverse- man stamps it with his identifying letter or letters, the serial number 4 SPIRIT LEVELING IN MASSACHUSETTS, 1922-35 of the station, and the year, using steel dies. If the tablet is set as a benchmark, the levelman stamps it with his identifying letter or letters, the serial number, and the year. Later, the figures of elevation to the nearest foot as determined by field computation are stamped with steel dies on those tablets that serve as benchmarks, which include many that were set to mark traverse stations.