Publisher's Synopsis
Excerpt from Geodesy Primary Triangulation on the One Hundred and Fourth in and on the Thirty-Ninth Parallel in Colorado, Utah, and Nevada by William Bowie
The length of the base as measured with rods is 11 meters. The reduction to sea level is meters; therefore the length of the base reduced to sea level is 11 1 meters. Since the length, as brought through the triangulation from the Provo base to the El Paso base, differed from the above value by one part in 13 500, it was decided to remeasure the El Paso base, and, if necessary, to insert an additional base in the one hundred and fourth meridian triangulation.
The length of the El Paso base reduced to sea level, as measured in 1913 with three invar tapes, is 11 2889852 meters. (see p.22.) There appeared to be no uncertainty whatever in the recovery of the ends of the base, nor was there any uncertainty in the recovery of the marks of the triangulation stations Pikes Peak, Divide, and Bison, the stations in or near the El Paso base net, from which the one hundred and fourth meridian triangulation started. Con sequently, the difference between the new and old measures of the El Paso base must be due to systematic or constant errors in one or both measures.
A careful study of the results of various standardizations of the same set of invar tapes (see table on p. 25) makes it seem reasonably certain that there is no constant error in the mean length of any group of three tapes as great as one part in 500 000. The iced bar is used at the Bureau of Standards in determining the length of the 50-meter comparator, and from time to time the iced bar has been compared directly with the prototype meter held at that bureau.
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