Ultra-cool Dwarfs from Large Area Surveys
  We selected brown dwarf candidates from the seventh Data Release of the Sloan
Digital Sky Survey (SDSS DR7) with new photometric selectioncriteria based on a
parameteriaztion of well-known L and T dwarfs. Then we confirmed their status
with SDSS spectra. The candidates without SDSS spectra are cross matched in the
Two Micron All Sky Survey (2MASS) and the Fourth Data Release of the UKIRT
Infrared Deep Sky Survey (UKIDSS DR4). With the help of colors based on SDSS,
2MASS and UKIDSS, we are able to estimate spectral types of our candidates. We
obtain reliable proper motions using positional and epoch information
downloaded direct from the survey databases.
