The Very Large Array (VLA), one of the world's premier astronomical radio observatories, consists 27 radio antennas in a 'Y'-shaped configuration at Socorro, New Mexico, USA. Each antenna is 25 meters in diameter and can be moved along rails to different positions. VLA is an interferometer; this means it operates by multiplying the data from each pair of the telescopes to form the interference patterns. The structure of those interference patterns, and how they change with time as earth rotates, reflect the structure of the radio sources on the sky. Table 3.1 shows the various 'Y' configurations in which VLA can be operates (see section 3.1.1.1).
The VLA telescope is very similar to the GMRT except for the operating frequencies. GMRT also has an approximate 'Y'-shaped configuration spread over 25 km area but each antenna is 45 meters in diameter and has fixed location. The difference between the two arrays is their range of operating frequencies. While VLA primarily caters to above 1400 MHz, GMRT operates below 1430 MHz. They are thus complimentary. So the VLA calibrators can be used for GMRT at 1420 MHz. And those can be used at 610 MHz by a bootstrapping method. (Ref : http://www.vla.nrao.edu/genpub/overview/)
The site co-ordinate of the VLA are:
latitude = 34 deg 04 min 43.497 sec north longitude = 107 deg 37 min 03.819 sec west altitude = 2124 m (6970 ft)