Notas sobre nivelamentos barométricos


  • Allyrio Hugueney de Mattos Diretor da Divisão de Cartografia do C.N.G.


Cartografia, Altimetria


Under the title Notes on barometric levelling the author discusses a previous paper in which barometers, aneroids and altimeters were analysed, he arrives to the conclusion that all of these instruments are used only in measuring atmospheric pressure and that the so called barometric levelling is used in order to derminate altitudes with the aid of usual formulas which, based on theoretical principles, establish a relation between altitude and barometric pressure. The author demonstrates, then, that the instruments denominated altimeters, either of English or American production, present scales based on atmospheric conditions which are obviously completely different from the ones prevailing in tropical climates, chiefly in what concerns to humidity. The author concludes by recomending the use of barometric rather than altimetric scales and stating, furthermore, that the use of the first method should be accompanied by measurings of the temperature as well as of the humidity. The author examines the various processes used, presents tables containing pertaining data and a graphic for current use and finally states that with the precautions mentioned it is possible to obtain altitudes with errors not greater than one meter.