Algorithms related to the observations of natural phenomenons. Most algorithms in this package are derived from empirical measurements; their results are approximative. Algorithms include:

- Sea water properties (density, sound velocity, fusion temperature, etc.) computed from salinity, temperature and pression using algorithms published by UNESCO.
- Values relative to earth calendar, like tropical year length.
- etc.

References
Alain Poisson, M.H. Gashoumi and Selim Morcos. Salinity and density of seawater: table for high salinities (42 to 50). Unesco technical papers in marine science #62 (1991). Unesco International oceanographic tables, volume 4. Unesco technical papers in marine science #40 (1987). Franck J. Millero. Solubility of oxygen in sea water in Progress on oceanographic tables and standards 1983-1986. Unesco technical papers in marine science #50 (1986) pp.13-14. Unesco The international system of units (SI) in oceanography. Unesco technical papers in marine science #45 (1985). N.P. Fofonoff and R.C. Millard Jr. Algorithms for computation of fundamental properties of seawater. Unesco technical papers in marine science #44 (1983). Tropical year length is computed using formula by Laskar (1986). Synodic month length is computed using formula by Chapront-Touze and Chapront (1988). Those formulas was taken from the following adress: http://webexhibits.org/calendars/year-astronomy.html http://www.treasure-troves.com/astro/TropicalYear.html