. Report of the Boundary commission upon the survey and re-marking of the boundary between the United States and Mexico west of the Rio Grande, 1891-1896 ... Ariz do d : : :::::::;::::::;:: 103. 40 103. 34 1-1722 ^ * The engineer in charge of the St. Louis survey states that there was a higher degree of accuracy noticedin the stadia work of the engineer who determined the wire interval; also, that a uniform difference in theaccuracy of work done by the several observers was shown by the computation of the coordiuatesof stadiastations,thus indicating a different personal equation for each
. Report of the Boundary commission upon the survey and re-marking of the boundary between the United States and Mexico west of the Rio Grande, 1891-1896 ... Ariz do d : : :::::::;::::::;:: 103. 40 103. 34 1-1722 ^ * The engineer in charge of the St. Louis survey states that there was a higher degree of accuracy noticedin the stadia work of the engineer who determined the wire interval; also, that a uniform difference in theaccuracy of work done by the several observers was shown by the computation of the coordiuatesof stadiastations,thus indicating a different personal equation for each observer. It should be noted that only the experiencedobserver can be said to have a personal equation, and this personal eciuation would be more and more constant andimportant with increasiuy experience. t In computing the average or working interval on this survey double weight was given to the observer whoused the transit. Doubling the number of observers doubled the time necessary for the determination without anycompeusatory gain in accuracy. For this reason a single observer is preferable. S. Doc. 257 19 234 UNITED STATES AND MEXICAN Ill tbis case, as in tlie oue givenabove, tbe ditterence between the ob-served intervals is seen to have a constantsign, name]}, each of Mr. values areless than the writers, though the difler- AilririilVss ence is small, being 1 in 1,722. rpjjg ]nf^i^ ijut |jy jiQ means the least, potent cause of systematic error in the sta-dia measurement of the Mexican bound-ary line remains to be discussed; but firsta few words of explanation. If, in determining the stadia interval,the transit bo centered a distance f+cback of the zero of the base line (see ), the angle formed by the upper andlower line of sight, constituting the stadiareading, will have its apex directly abovethe zero of the base line. Xow, if it werenot for the influence of differential refrac-tion, the intercept on the stadia rod heldat any i)Oint on the
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