Keyword      Data type       Meaning
ID          LONG           Object ID 
RA          FLOAT          Right ascension in J2000 (degree)
DEC         FLOAT          Declination in J2000 (degree)
sigRA       FLOAT          Error of RA (mas)
sigDEC      FLOAT          Error of DEC (mas)
PMRA        FLOAT          Proper motion in right ascension multiplied by cos($\delta$) (mas/yr) 
PMDEC       FLOAT          Proper motion in declination (mas/yr)
sigPMRA     FLOAT          Error of proper motion in right ascension
sigPMDEC    FLOAT          Error of proper motion in declination
MAG         FLOAT          SCUSS automatic magnitude
TYPE        INTEGER        Star/galaxy classification (0 for star; others for galaxy)
OBSNUM      INTEGER        Number of epoches
MeanEpoch   FLOAT          Mean epoch
MinEpoch    FLOAT          Minimum epoch
MaxEpoch    FLOAT          Maximal epoch

Our proper motion catalog contains about 7.7 million objects. Objects information includes  ID, positions, astrometric parameters,object classifications as well as  information about observation data used in the process of calculation of  proper motions. The equatorial coordinate in J2000 is used to specify the positions of objects. The unit of coordinate is degree. It is noteworthy that the unit of coordinate error is mas. The 'PMRA' column contains the proper motion in right ascension  multiplied by cos delta. The 'PMDEC' column contains the proper motion in declination. The unit of proper motion is mas/yr. We also provide the SCUSS auto magnitude in 'MAG' column. The 'code' column contains the classification of source, the classification from GSC is updated by classification from SDSS, 0 means star, 3 or 4 means galaxy.  The last 4 columns are the information about observation data used in proper motion calculation including the sum of observations, the mean, minimum and maximal epoch of observations used in the calculation.