SDSS objects that match to USNO-B objects have their match parameters stored here.

deltareal4arcsecPOS_ANG_DIST_GENERALPosition difference between catalog and photo object (r' band)
matchint4 CODE_MISC1: successful match to catalog within 1.0 arcsec
propermotionreal40.01 arcsec/yPOS_PMProper motion of object
anglereal4degPOS_PM_PADirection of proper motion (+N through E)
bluereal4magPHOT_MAG_BBlue magnitude of matching USNO object
redreal4magPHOT_MAG_RRed magnitude of matching USNO object
objIDbigint8 ID_MAINunique id, points to photoObj