Here are some examples of using
stilts tmatch2 in1=obs_v.xml in2=obs_i.xml out=obs_iv.xml \ matcher=sky values1="ra dec" values2="ra dec" params="2"
stilts tmatch2 survey.fits ifmt2=csv mycat.csv \ icmd1='addskycoords fk4 fk5 RA1950 DEC1950 RA2000 DEC2000' \ matcher=skyerr \ params=10 values1="RA2000 DEC2000 POS_ERR" values2="RA DEC 0" \ join=2not1 omode=count
skyerrmatcher is used, which takes account of this; the third entry in the
values1parameter is the POS_ERR column (in arcsec). Since the second input table has no positional uncertainty information, 0 is used as the third entry in
paramsgives a rough idea of the scale of the object separations, but its value does not affect the result. The join type is
2not1, which means the output table will only contain those entries which are in the second input table but not in the first one. The output table is not stored, but the number of rows it contains (the number of objects represented in the CSV file but not the survey) is written to the screen.
stilts tmatch2 ifmt1=ascii ifmt2=ascii in1=cat-a.txt in2=cat-b.txt \ matcher=2d values1='X Y' values2='X Y' params=5 join=1and2 \ suffix1=_a suffix2=_b \ ocmd='addcol XDIFF X_a-X_b; addcol YDIFF Y_a-Y_b' \ ocmd'keepcols "XDIFF YDIFF"' omode=stats
suffix*parameters describe how the input X and Y columns are to be renamed to avoid duplicate column names in the output table. To this result are added two new columns, representing the X and Y positional difference between the rows from one input table and those from the other. The
keepcolsfilter then throws all the other columns away, retaining only these difference columns. The final two-column table is not stored anywhere, but (
omode=stats) statistics including mean and standard deviation are calculated on its columns and displayed to the screen. Having done all this, you can examine the average X and Y differences between the two input tables for matched rows, and if they differ significantly from zero, you can conclude that there is a systematic error between the positions in the two input files.
stilts tmatch2 in1=mgc.fits in2=6dfgs.xml join=1and2 find=all \ matcher=sky+1d params='3 0.5' \ values1='ra dec bmag' values2='RA2000 DEC2000 B_MAG" \ out=pairs.fits
1dmatch criteria. This means that the only rows which match are those which are both within 3 arcsec of each other on the sky and and within 0.5 blue magnitudes. Note that for both the
values2parameters, the items for the
skymatcher (RA and DEC) are listed first, followed by those for the
1dmatcher (in this case, blue magnitude).