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In the same paper Bianchi et al. (2011, MNRAS, 411, 2770) matched their catalogs of unique UV sources to the seventh SDSS data release (DR7)
The matched sources have up to 7 magnitudes: GALEX FUV and NUV, and SDSS u g r i z . The area coverage of the overlap between the two surveys is shown in the Figure below. Table 1 of Bianchi et al. (2011) provides the area coverage for the matched source catalog, total and divided by latitude.

Overlap between GALEX DR5 and SDSS DR7 (AIS: yellow, MIS: green), in galactic coordinates.

GALEX-MIS - SDSS Matched Catalogs (6 million sources)
These 3 tarfiles contain 23 files, each covering a 5 degree band of Galactic latitude.

MIS GALEX magnitudes (0.4G) (GR5xDR7_*_*_gmags.mis.dat)
MIS SDSS magnitudes (0.3G) (GR5xDR7_*_*_smags.mis.dat)
MIS SDSS flags (0.2G) (GR5xDR7_*_*_sflags.mis.dat)

GALEX-AIS - SDSS Matched Catalogs (14.5 million sources)
These 3 tarfiles contain 180 files, each covering a 1 degree band of Galactic latitude.

AIS GALEX magnitudes (0.8G) (GR5xDR7_*_*_gmags.ais.dat)
AIS SDSS magnitudes (0.7G) (GR5xDR7_*_*_smags.ais.dat)
AIS SDSS flags (0.5G) (GR5xDR7_*_*_sflags.ais.dat)

These files contain the matched GALEX-SDSS objects resulting from searching the GALEX coordinates of objects in the "GALEX unique sources catalogs" described above against the SDSS PhotoPrimary table. They correpond to columns 6 and 7 of Table 2 in Bianchi et al. (2011, MNRAS, 411, 2770). A match radius of 3 arcsec was used in constructing final matched catalogs (see paper for details).

For each survey (MIS, AIS) the data are split among three files:
GR5xDR7_*_*_gmags.[m/a]is.dat, GR5xDR7_*_*_smags.[m/a]is.dat, and GR5xDR7_*_*_sflags.[m/a]is.dat.

There is a one-to-one correspondence between each line of all three files. For example, the 5th line of the "smags" and "sflags" files contain information on the SDSS object that matches the GALEX object listed in the 5th line of the "gmags" file.

A GALEX source may have multiple SDSS matches, due to the higher SDSS spatial resolution. Sources with multiple matches are not useful for color analyses (the GALEX magnitudes may be a composite of nearby sources), therefore we introduced a flag whereby sources with multiple optical matches can be identified.
SDSS sources are assigned a "rank" with the following meaning:

rank = 0: One (and only one) SDSS source matched the GALEX source
rank = 1: Multiple SDSS sources matched to GALEX source, with this being the closest

Space-separated columns contained in the files are listed below. Detailed descriptions for the GALEX field descriptions are given at the MAST GALEX site, and for the SDSS fields at the CAS SDSS site, under Tables, PhotoObjAll.

-- GR5xDR7_*_*_gmags.[m/a]is.dat --

Contains information on GALEX sources, plus the matched SDSS objid (listed below as "sdssid") as well as the "rank" flag. Included fields are:


-- GR5xDR7_*_*_smags.[m/a]is.dat --

Contains mainly magnitude information on SDSS sources. Included fields are:

#objid,ra,dec,dist,type, petromag_u,petromagerr_u,petromag_g,petromagerr_g,petromag_r,petromagerr_r, petromag_i,petromagerr_i,petromag_z,petromagerr_z,specobjid, propermotion,usno_blue,usno_red,rank

NOTE: "objid" here is the SDSS objid, and "ra" and "dec" are the SDSS photometric coordinates; "dist" is the distance from the corresponding GALEX source coordinates in arcmin; "rank" is described above. USNO magnitudes are from the USNO database, described at the CAS SDSS site, under Tables, USNO.

-- GR5xDR7_*_*_sflags.[m/a]is.dat --

Contains mainly photometry-flag information on SDSS sources. The individual flags (e.g, "_sat" for saturation or "_cr" for cosmic ray) for the different magnitudes (u,g,r,i,z) were extracted from SDSS "flags" field. Included fields are:

#objid,edge,u_sat,u_cr,g_sat,g_cr,r_sat,r_cr,i_sat,i_cr,z_sat,z_cr, flags,flags_u,flags_g,flags_r,flags_i,flags_z,ra,dec