Carlos Ibáñez e Ibáñez de Ibero

International scientific collaboration in geodesy and calls for an international standard unit of length

← Previous revision Revision as of 08:14, 2 May 2026 Line 64: Line 64: President of the Permanent Commission of the European Arc Measurement from 1874 to 1886, Ibáñez became the first president of the [[International Association of Geodesy|International Geodetic Association]] (1887–1891) after the death of [[Johann Jacob Baeyer]].<ref name=":6" /><ref name=":14" /> Under Ibáñez's presidency, the International Geodetic Association acquired a global dimension with the accession of the United States, Mexico, Chile, [[Argentina]] and Japan.<ref name=":20" /><ref>{{Cite journal|last=Torge|first=W.|date=April 1, 2005|title=The International Association of Geodesy 1862 to 1922: from a regional project to an international organization|journal=Journal of Geodesy|volume=78|issue=9|pages=558–568|doi=10.1007/s00190-004-0423-0|bibcode=2005JGeod..78..558T|s2cid=120943411|issn=1432-1394}}</ref><ref name=":6" /> President of the Permanent Commission of the European Arc Measurement from 1874 to 1886, Ibáñez became the first president of the [[International Association of Geodesy|International Geodetic Association]] (1887–1891) after the death of [[Johann Jacob Baeyer]].<ref name=":6" /><ref name=":14" /> Under Ibáñez's presidency, the International Geodetic Association acquired a global dimension with the accession of the United States, Mexico, Chile, [[Argentina]] and Japan.<ref name=":20" /><ref>{{Cite journal|last=Torge|first=W.|date=April 1, 2005|title=The International Association of Geodesy 1862 to 1922: from a regional project to an international organization|journal=Journal of Geodesy|volume=78|issue=9|pages=558–568|doi=10.1007/s00190-004-0423-0|bibcode=2005JGeod..78..558T|s2cid=120943411|issn=1432-1394}}</ref><ref name=":6" />

The progresses of [[metrology]] combined with those of [[gravimetry]] through improvement of [[Kater's pendulum]] led to a new era of [[geodesy]]. If precision metrology had needed the help of geodesy, it could not continue to prosper without the help of metrology. It was then necessary to define a single unit to express all the measurements of terrestrial arcs, and all determinations of the [[gravitational acceleration]] by the means of pendulum. Metrology had to create a common unit, adopted and respected by all civilized nations. Moreover, at that time, statisticians knew that scientific observations are marred by two distinct types of errors, [[Observational error|constant errors]] on the one hand, and [[Randomness|fortuitous]] errors, on the other hand. The effects of random errors can be mitigated by the [[least squares]] method. Constant or systematic errors on the contrary must be carefully avoided, because they arise from one or more causes which constantly act in the same way, and have the effect of always altering the result of the experiment in the same direction. They therefore deprive of any value the observations that they impinge. It was thus crucial to compare at controlled temperatures with great precision and to the same unit all the standards for measuring geodesic bases, and all the pendulum rods. Only when this series of metrological comparisons would be finished with a probable error of a thousandth of a millimetre would geodesy be able to link the works of the different nations with one another, and then proclaim the result of the measurement of the Globe.<ref name=":15">{{Cite book|last=Ibáñez e Ibáñez de Ibero|first=Carlos|url=http://www.rac.es/ficheros/Discursos/DR_20080825_173.pdf|title=Discursos leidos ante la Real Academia de Ciencias Exactas Fisicas y Naturales en la recepcion pública de Don Joaquin Barraquer y Rovira|publisher=Imprenta de la Viuda e Hijo de D.E. Aguado|year=1881|location=Madrid|pages=70, 78}}</ref><ref name=":24">{{Cite book|last=Ritter|first=Élie|url=https://play.google.com/books/reader?id=IVEDAAAAQAAJ&hl=fr&pg=GBS.PA7|title=Manuel théorique et pratique de l'application de la méthode des moindres carrés: au calcul des observations|date=1858|publisher=Mallet-Bachelier|pages=7–8|language=fr}}</ref> In 1901, [[Friedrich Robert Helmert]] found, mainly by [[gravimetry]], parameters of the ellipsoid remarkably close to reality. Although marked by the concern to correct [[vertical deflection]]s, taking into account the contributions of gravimetry, research between 1910 and 1950 remained practically limited to large continental triangulations. The most significant work would be that by [[John Fillmore Hayford]], which relied mainly on the North American national network. His ellipsoid was adopted in 1924 by the [[International Union of Geodesy and Geophysics]].<ref name=":33">{{Cite book|title=Géodésie in Encyclopedia Universalis|publisher=Encyclopedia Universalis|year=1996|isbn=978-2-85229-290-1|pages=Vol 10, p. 302|oclc=36747385}}</ref> The progresses of [[metrology]] combined with those of [[gravimetry]] through improvement of [[Kater's pendulum]] led to a new era of [[geodesy]]. If precision metrology had needed the help of geodesy, it could not continue to prosper without the help of metrology. It was then necessary to define a single unit to express all the measurements of terrestrial arcs, and all determinations of the [[gravitational acceleration]] by the means of pendulum. Metrology had to create a common unit, adopted and respected by all civilized nations. Moreover, at that time, statisticians knew that scientific observations are marred by two distinct types of errors, [[Observational error|constant errors]] on the one hand, and [[Randomness|fortuitous]] errors, on the other hand. The effects of random errors can be mitigated by the [[least squares]] method. Constant or systematic errors on the contrary must be carefully avoided, because they arise from one or more causes which constantly act in the same way, and have the effect of always altering the result of the experiment in the same direction. They therefore deprive of any value the observations that they impinge. It was thus crucial to compare at controlled temperatures with great precision and to the same unit all the standards for measuring geodesic bases, and all the pendulum rods. Only when this series of metrological comparisons would be finished with a probable error of a thousandth of a millimetre would geodesy be able to link the works of the different nations with one another, and then proclaim the result of the measurement of the Globe.<ref name=":15">{{Cite book|last=Ibáñez e Ibáñez de Ibero|first=Carlos|url=http://www.rac.es/ficheros/Discursos/DR_20080825_173.pdf|title=Discursos leidos ante la Real Academia de Ciencias Exactas Fisicas y Naturales en la recepcion pública de Don Joaquin Barraquer y Rovira|publisher=Imprenta de la Viuda e Hijo de D.E. Aguado|year=1881|location=Madrid|pages=70, 78}}</ref><ref name=":24" /> In 1901, [[Friedrich Robert Helmert]] found, mainly by [[gravimetry]], parameters of the ellipsoid remarkably close to reality. Although marked by the concern to correct [[vertical deflection]]s, taking into account the contributions of gravimetry, research between 1910 and 1950 remained practically limited to large continental triangulations. The most significant work would be that by [[John Fillmore Hayford]], which relied mainly on the North American national network. His ellipsoid was adopted in 1924 by the [[International Union of Geodesy and Geophysics]].<ref name=":33">{{Cite book|title=Géodésie in Encyclopedia Universalis|publisher=Encyclopedia Universalis|year=1996|isbn=978-2-85229-290-1|pages=Vol 10, p. 302|oclc=36747385}}</ref>

In 1889 the [[General Conference on Weights and Measures]] met at [[Sèvres]], the seat of the International Bureau. It performed the first great deed dictated by the motto inscribed in the pediment of the splendid edifice that is the metric system: "''A tous les temps, à tous les peuples''" (For all times, to all peoples); and this deed consisted in the approval and distribution, among the governments of the states supporting the Metre Convention, of prototype standards of hitherto unknown precision intended to propagate the metric unit throughout the whole world. These prototypes were made of a platinum-iridium alloy which combined all the qualities of hardness, permanence, and resistance to chemical agents which rendered it suitable for making into standards required to last for centuries. Yet their high price excluded them from the ordinary field of science.<ref name=":18">{{Cite web|last=Guillaume|first=Charles-Édouard|year=1920|title=The Nobel Prize in Physics 1920|url=https://www.nobelprize.org/prizes/physics/1920/guillaume/lecture/|access-date=September 19, 2020|publisher=Nobel Foundation|pages=1, 2}}</ref> For metrology the matter of expansibility was fundamental; as a matter of fact the temperature measuring error related to the length measurement in proportion to the expansibility of the standard and the constantly renewed efforts of metrologists to protect their measuring instruments against the interfering influence of temperature revealed clearly the importance they attached to the expansion-induced errors. It was common knowledge, for instance, that effective measurements were possible only inside a building, the rooms of which were well protected against the changes in outside temperature, and the very presence of the observer created an interference against which it was often necessary to take strict precautions. Thus, the Contracting States also received a collection of thermometers which accuracy made it possible to ensure that of length measurements.<ref name=":18" /><ref name=":17" /> In 1889 the [[General Conference on Weights and Measures]] met at [[Sèvres]], the seat of the International Bureau. It performed the first great deed dictated by the motto inscribed in the pediment of the splendid edifice that is the metric system: "''A tous les temps, à tous les peuples''" (For all times, to all peoples); and this deed consisted in the approval and distribution, among the governments of the states supporting the Metre Convention, of prototype standards of hitherto unknown precision intended to propagate the metric unit throughout the whole world. These prototypes were made of a platinum-iridium alloy which combined all the qualities of hardness, permanence, and resistance to chemical agents which rendered it suitable for making into standards required to last for centuries. Yet their high price excluded them from the ordinary field of science.<ref name=":18">{{Cite web|last=Guillaume|first=Charles-Édouard|year=1920|title=The Nobel Prize in Physics 1920|url=https://www.nobelprize.org/prizes/physics/1920/guillaume/lecture/|access-date=September 19, 2020|publisher=Nobel Foundation|pages=1, 2}}</ref> For metrology the matter of expansibility was fundamental; as a matter of fact the temperature measuring error related to the length measurement in proportion to the expansibility of the standard and the constantly renewed efforts of metrologists to protect their measuring instruments against the interfering influence of temperature revealed clearly the importance they attached to the expansion-induced errors. It was common knowledge, for instance, that effective measurements were possible only inside a building, the rooms of which were well protected against the changes in outside temperature, and the very presence of the observer created an interference against which it was often necessary to take strict precautions. Thus, the Contracting States also received a collection of thermometers which accuracy made it possible to ensure that of length measurements.<ref name=":18" /><ref name=":17" /> Line 80: Line 80: In order to avoid the difficulty in exactly determining the temperature of a bar by the mercury thermometer, [[Friedrich Wilhelm Bessel]], inspired by [[Jean-Charles de Borda]], introduced in 1834 near [[Königsberg]] a compound bar which constituted a metallic thermometer. A [[zinc]] bar was laid on an [[iron]] bar two toises long, both bars being perfectly planed and in free contact, the zinc bar being slightly shorter and the two bars rigidly united at one end. As the temperature varied, the difference of the lengths of the bars, as perceived by the other end, also varied, and afforded a quantitative correction for temperature variations, which was applied to reduce the length to standard temperature. During the measurement of the base line the bars were not allowed to come into contact, the interval being measured by the insertion of glass wedges. The results of the comparisons of four measuring rods with one another and with the standards were elaborately computed by the method of [[Least squares|least-squares]].<ref>{{cite EB1911|wstitle=Geodesy |volume= 11 |last1 = Clarke|first1= Alexander Ross |last2= Helmert|first2= Friedrich Robert |pages= 607–615}}</ref> Indeed, before [[invar]]'s discovery, geodesists tried to assess temperature effect on measuring devices in order to avoid [[Observational error|observational errors]].<ref name="Guillaume 1906 242–263" /> In order to avoid the difficulty in exactly determining the temperature of a bar by the mercury thermometer, [[Friedrich Wilhelm Bessel]], inspired by [[Jean-Charles de Borda]], introduced in 1834 near [[Königsberg]] a compound bar which constituted a metallic thermometer. A [[zinc]] bar was laid on an [[iron]] bar two toises long, both bars being perfectly planed and in free contact, the zinc bar being slightly shorter and the two bars rigidly united at one end. As the temperature varied, the difference of the lengths of the bars, as perceived by the other end, also varied, and afforded a quantitative correction for temperature variations, which was applied to reduce the length to standard temperature. During the measurement of the base line the bars were not allowed to come into contact, the interval being measured by the insertion of glass wedges. The results of the comparisons of four measuring rods with one another and with the standards were elaborately computed by the method of [[Least squares|least-squares]].<ref>{{cite EB1911|wstitle=Geodesy |volume= 11 |last1 = Clarke|first1= Alexander Ross |last2= Helmert|first2= Friedrich Robert |pages= 607–615}}</ref> Indeed, before [[invar]]'s discovery, geodesists tried to assess temperature effect on measuring devices in order to avoid [[Observational error|observational errors]].<ref name="Guillaume 1906 242–263" />

In the 19th century, statisticians knew that scientific observations were subject to two types of error: constant errors and random errors. The effects of the latter could be corrected using the [[Least squares|least squares method]]. Constant errors, on the other hand, had to be carefully avoided, as they were caused by various factors that consistently altered the results of observations in the same direction. These errors thus tended to render the results they affected worthless. Consider, for example, measuring a straight line to determine its length in metres. If a metal ruler is used for this measurement, and an error is made in determining the temperature at which its length corresponds to that of a metre, all observations will be affected by a consistent error stemming from this error, and no matter how many times the operation is repeated, it will be impossible to obtain an accurate result. If, on the contrary, we know exactly the temperature at which the ruler is equivalent to the metre and if the error affects the actual temperature of the ruler in the different observations, each observation will be affected by a random error, but these errors will occur sometimes in one direction and sometimes in the other, and by repeating the operation a large number of times we can hope to eliminate their effect by compensating for them.<ref>{{Cite book |last=Ritter |first=Elie |url=https://play.google.com/store/books/details?id=FLEWAAAAQAAJ&rdid=book-FLEWAAAAQAAJ&rdot=1 |title=Manuel théorique et pratique de l'application de la méthode des moindres carrés au calcul des observations |date=1858 |publisher=Mallet-Bachelier |pages=7–8 |language=fr}}</ref> In the 19th century, statisticians knew that scientific observations were subject to two types of error: constant errors and random errors. The effects of the latter could be corrected using the [[Least squares|least squares method]]. Constant errors, on the other hand, had to be carefully avoided, as they were caused by various factors that consistently altered the results of observations in the same direction. These errors thus tended to render the results they affected worthless. Consider, for example, measuring a straight line to determine its length in metres. If a metal ruler is used for this measurement, and an error is made in determining the temperature at which its length corresponds to that of a metre, all observations will be affected by a consistent error stemming from this error, and no matter how many times the operation is repeated, it will be impossible to obtain an accurate result. If, on the contrary, we know exactly the temperature at which the ruler is equivalent to the metre and if the error affects the actual temperature of the ruler in the different observations, each observation will be affected by a random error, but these errors will occur sometimes in one direction and sometimes in the other, and by repeating the operation a large number of times we can hope to eliminate their effect by compensating for them.<ref name=":24">{{Cite book |last=Ritter |first=Elie |url=https://play.google.com/store/books/details?id=FLEWAAAAQAAJ&rdid=book-FLEWAAAAQAAJ&rdot=1 |title=Manuel théorique et pratique de l'application de la méthode des moindres carrés au calcul des observations |date=1858 |publisher=Mallet-Bachelier |pages=7–8 |language=fr}}</ref>

In the absence of a standard temperature scale, inconsistencies arose when attempting to link geodetic surveys from different countries to create a European geodetic network. In 1886, [[Adolphe Hirsch|Adolphe Hisch]], secretary of the [[General Conference on Weights and Measures|International Committee for Weights and Measures]] (CIPM) and of the [[International Association of Geodesy|International Geodetic Association]], proposed that all the toises that had served as geodetic standards in Europe during the 19th century be compared at the BIPM with the Toise of Peru and with the new [[History of the metre#International prototype metre|international metre]] so that the measurements made until then could be used to measure the Earth.<ref name=":13">{{Cite journal |last=Seligmann |first=A. E. M. |date=January 1923 |title=La Toise de Belgique |url=https://ui.adsabs.harvard.edu/abs/1923C&T....39...25S/abstract |journal=Ciel et Terre |language=en |volume=39 |pages=25 |bibcode=1923C&T....39...25S |issn=0009-6709}}</ref> The result of these comparisons made it possible to reduce the arcs measured in Germany to the metre. The discordance of {{Sfrac|1|66 000}} which remained between the triangles common to the German and French networks could be reduced to {{Sfrac|1|600 000}} which was at the limit of [[Accuracy and precision|accuracy]] of geodetic surveys at the time.<ref name="Pérard-1957">{{Cite web |last=Pérard |first=Albert |date=1957 |title=Carlos Ibáñez e Ibáñez de Ibero (14 avril 1825 – 29 janvier 1891), par Albert Pérard (inauguration d'un monument élevé à sa mémoire) |url=https://www.academie-sciences.fr/pdf/eloges/ibanez_notice.pdf |website=Institut de France – Académie des sciences |pages=26–28}}</ref> In fact, the length of Bessel's Toise, which according to the then legal ratio between the metre and the Toise of Peru, should be equal to 1.9490348 m, would be found to be 26.2·10⁻⁶ m greater during measurements carried out by [[Justin-Mirande René Benoit|Jean-René Benoît]] at the BIPM.<ref>Charles-Édouard Guillaume, ''La création du Bureau international des poids et mesures et son œuvre'', Paris, Gauthier-Villars, 1927, 321 <abbr>p.</abbr>, <abbr>p.</abbr> 130</ref><ref name="Hirsch-1892" /> It was the consideration of the divergences between the different toises used by geodesists that led the [[International Association of Geodesy|European Arc Measurement]] ({{langx|de|Europäische Gradmessung|links=no}} ) to consider, at the meeting of its Permanent Commission in [[Neuchâtel]] in 1866, the founding of a World Institute for the Comparison of Geodetic Standards, the first step towards the creation of the BIPM.<ref name="Guillaume-1916" /> Careful comparisons with several standard toises showed that the international metre calibrated on the ''[[History of the metre#Mètre des Archives|Mètre des Archives]]'' was not exactly equal to the legal metre or 443.296 lines of the toise, but, in round numbers, {{Sfrac|1|75 000}} of the length smaller,<ref name=":2" /> or approximately 0.013 millimetres. By contrast, in 2007, a comparison of the American Committee meter and its Swiss counterpart was carried out at [[National Institute of Standards and Technology|NIST]] and [[Federal Institute of Metrology|METAS]]. The two metre standards can be considered perfectly equivalent, with a difference of only (0.96 ±3.0) [[Micrometre|micrometers]]. The poor quality of the measuring surfaces explained the significant uncertainty in the measurements compared to today's standards.<ref>{{Cite web |date=2007 |title=Key comparison of the Committee Meter |url=https://www.f-r-hassler.ch/downloads/mass_gewicht/Beil-03-1.pdf |website=e-expo: Ferdinand Rudolf Hassler}}</ref> In the absence of a standard temperature scale, inconsistencies arose when attempting to link geodetic surveys from different countries to create a European geodetic network. In 1886, [[Adolphe Hirsch|Adolphe Hisch]], secretary of the [[General Conference on Weights and Measures|International Committee for Weights and Measures]] (CIPM) and of the [[International Association of Geodesy|International Geodetic Association]], proposed that all the toises that had served as geodetic standards in Europe during the 19th century be compared at the BIPM with the Toise of Peru and with the new [[History of the metre#International prototype metre|international metre]] so that the measurements made until then could be used to measure the Earth.<ref name=":13">{{Cite journal |last=Seligmann |first=A. E. M. |date=January 1923 |title=La Toise de Belgique |url=https://ui.adsabs.harvard.edu/abs/1923C&T....39...25S/abstract |journal=Ciel et Terre |language=en |volume=39 |pages=25 |bibcode=1923C&T....39...25S |issn=0009-6709}}</ref> The result of these comparisons made it possible to reduce the arcs measured in Germany to the metre. The discordance of {{Sfrac|1|66 000}} which remained between the triangles common to the German and French networks could be reduced to {{Sfrac|1|600 000}} which was at the limit of [[Accuracy and precision|accuracy]] of geodetic surveys at the time.<ref name="Pérard-1957">{{Cite web |last=Pérard |first=Albert |date=1957 |title=Carlos Ibáñez e Ibáñez de Ibero (14 avril 1825 – 29 janvier 1891), par Albert Pérard (inauguration d'un monument élevé à sa mémoire) |url=https://www.academie-sciences.fr/pdf/eloges/ibanez_notice.pdf |website=Institut de France – Académie des sciences |pages=26–28}}</ref> In fact, the length of Bessel's Toise, which according to the then legal ratio between the metre and the Toise of Peru, should be equal to 1.9490348 m, would be found to be 26.2·10⁻⁶ m greater during measurements carried out by [[Justin-Mirande René Benoit|Jean-René Benoît]] at the BIPM.<ref>Charles-Édouard Guillaume, ''La création du Bureau international des poids et mesures et son œuvre'', Paris, Gauthier-Villars, 1927, 321 <abbr>p.</abbr>, <abbr>p.</abbr> 130</ref><ref name="Hirsch-1892" /> It was the consideration of the divergences between the different toises used by geodesists that led the [[International Association of Geodesy|European Arc Measurement]] ({{langx|de|Europäische Gradmessung|links=no}} ) to consider, at the meeting of its Permanent Commission in [[Neuchâtel]] in 1866, the founding of a World Institute for the Comparison of Geodetic Standards, the first step towards the creation of the BIPM.<ref name="Guillaume-1916" /> Careful comparisons with several standard toises showed that the international metre calibrated on the ''[[History of the metre#Mètre des Archives|Mètre des Archives]]'' was not exactly equal to the legal metre or 443.296 lines of the toise, but, in round numbers, {{Sfrac|1|75 000}} of the length smaller,<ref name=":2" /> or approximately 0.013 millimetres. By contrast, in 2007, a comparison of the American Committee meter and its Swiss counterpart was carried out at [[National Institute of Standards and Technology|NIST]] and [[Federal Institute of Metrology|METAS]]. The two metre standards can be considered perfectly equivalent, with a difference of only (0.96 ±3.0) [[Micrometre|micrometers]]. The poor quality of the measuring surfaces explained the significant uncertainty in the measurements compared to today's standards.<ref>{{Cite web |date=2007 |title=Key comparison of the Committee Meter |url=https://www.f-r-hassler.ch/downloads/mass_gewicht/Beil-03-1.pdf |website=e-expo: Ferdinand Rudolf Hassler}}</ref>