Method for generating and optimizing a spectral database that can be used in a process for characterizing a target product by topological spectral analysis from a limited number of available standards, method consisting of a first step performing the same spectral analysis on said standards, and to constitute from the spectra obtained a spectral database A at several wavelengths and/or ranges of wavelengths, characterized in a second step in which the "polluting" wavelengths and/or ranges of wavelengths from said spectral database A are eliminated from the spectral database A, second step consisting of 1. to repeat at least twice, preferably at least three times, more preferably at least five times the same spectral analysis as that carried out during the first step, and this on at least one of the available standards, preferably on at least two or even all of said available standards; 2. to build a spectral database B from the measurements made in point 1 above; 3. to calculate for each standard selected in point 1 above and for each wavelength and/or range of wavelengths of the spectral database A the standard deviations σ of the measurements recorded in the database B; 4. to identify in the database B the wavelengths and/or range of wavelengths for which the standard deviation is greater than a predetermined value; and 5. to delete from the spectral database A the measurements corresponding to the wavelengths identified in point 4 above and thus obtain an improved spectral database A', and also characterized by a third consecutive step which consists of expanding the improved spectral database A', step consisting of carrying out combinations of several standards of the first step and populating the improved spectral database A' with of said combinations called synthetic standards or "IG" intergerms and thus obtain an expanded spectral database E. method consisting of a first step performing the same spectral analysis on said standards, and to constitute from the spectra obtained a spectral database A at several wavelengths and/or ranges of wavelengths, characterized in a second step in which the "polluting" wavelengths and/or ranges of wavelengths from said spectral database A are eliminated from the spectral database A, second step consisting of 1. to repeat at least twice, preferably at least three times, more preferably at least five times the same spectral analysis as that carried out during the first step, and this on at least one of the available standards, preferably on at least two or even all of said available standards; 2. to build a spectral database B from the measurements made in point 1 above; 3. to calculate for each standard selected in point 1 above and for each wavelength and/or range of wavelengths of the spectral database A the standard deviations σ of the measurements recorded in the database B; 4. to identify in the database B the wavelengths and/or range of wavelengths for which the standard deviation is greater than a predetermined value; and 5. to delete from the spectral database A the measurements corresponding to the wavelengths identified in point 4 above and thus obtain an improved spectral database A', and also characterized by a third consecutive step which consists of expanding the improved spectral database A', step consisting of carrying out combinations of several standards of the first step and populating the improved spectral database A' with of said combinations called synthetic standards or "IG" intergerms and thus obtain an expanded spectral database E. 1. to repeat at least twice, preferably at least three times, more preferably at least five times the same spectral analysis as that carried out during the first step, and this on at least one of the available standards, preferably on at least two or even all of said available standards; 2. to build a spectral database B from the measurements made in point 1 above; 3. to calculate for each standard selected in point 1 above and for each wavelength and/or range of wavelengths of the spectral database A the standard deviations σ of the measurements recorded in the database B; 4. to identify in the database B the wavelengths and/or range of wavelengths for which the standard deviation is greater than a predetermined value; and 5. to delete from the spectral database A the measurements corresponding to the wavelengths identified in point 4 above and thus obtain an improved spectral database A',