Large ongoing projects, such as the Sloan Digital Sky Survey (SDSS) [123][22][83], aim at creating a comprehensive digital map of the northern sky. The project SDSS will result in a complex archive of about 20 terabytes containing exquisitely calibrated digital images of the accessible half of the northern sky, in 5 wavelength bands, from the ultraviolet to the infrared. A processing pipeline will identify and derive parameters (fluxes, sizes, colors) of over 100 million objects, classify them by type (star, galaxy, quasar) and obtain high resolution spectral information for the brightest one million galaxies and 100,000 quasars in the survey area. All this information will be placed into the archive for subsequent access and analysis.
The huge amount of information involved
makes storage and access a formidable computational challenge.
The data is organized as points in .
Typically the dimension
is fairly low,
e.g.,
: right ascension, declination, five colors, redshift.