observational benchmark of galaxy properties at redshift z > 1. The survey is using near-infrared FOURSTAR instrument on the Magellan Telescopes, surveying in all three HST legacy fields: COSMOS, CDFS, and UDS. Because of the demands on observing time required to obtain spectroscopic redshifts (i.e., redshifts determined directly from spectral features measured at high precision), a common alternative is to use photometric redshifts based on model fits to the brightnesses and colors of objects. Such "photo-z's" can be used in large surveys to estimate the spatial distribution of galaxies and quasars, provided the galaxy types and colors are well understood in a particular redshift range. At present, the errors on photometric redshift measurements are significantly higher than those of spectroscopic redshifts, but future surveys (for example, the LSST) aim to significantly refine the technique. See also Baryon acoustic oscillations Intensity mapping Large-scale structure of the cosmos Redshift-space distortions References External links Probes of Large Scale Structure List of galaxy redshift surveys Physical cosmology Observational astronomy Large-scale structure of the cosmos