Accuracy of Results

CHAPTER VI.

Quantities of Materials.

I. Volumes from Cross Sections.

3. Volumes of Continuous Prismoids.

a. Volumes from Plotted Sections.

Accuracy of Results.

As to the degree of accuracy in results of measurements made in the manner just described, it is evident that the nearer together the cross-sections are taken and the nearer will the prismoids conform to the actual condition of the surface of the ground, but in every case the accuracy of the measurement with the Planimeter is far within the accuracy of the cross-sections and of the field work and with accurate data and accurate plotting the volume of excavation found by this method will be well within the degree of accuracy obtainable by any other known means.

As to the saving in time and labor, it is too evident to need any discussion and a statement of the results of comparative tests of this with other methods would seem like exaggeration until the reader had tested the matter for himself.

Mr. Herschell in the article already referred to says as the results of comparative tests made by himself that the “saving of time derived from the use of the Planimeter over that required by calculating from tables or from formulas, was as 1/2 to 4/5”, and that the degree of accuracy practically attained “surpasses what in any ordinary work has hitherto been considered practically attainable.” He also estimates the probable error as not greater than two yards in one thousand. It will take but little experience with this form of calculation to prove all of these estimates both as to saving of time and accuracy to be well upon the conservative side.

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