For uvdata sets obtained from different correlator configurations, the header frequency structure in the Miriad data could differ in the interested data files. Users might calibrate the individual data sets first. Then, using linetype in Miriad, users may redo the grid of the spectral visibility data along the frequency axis by selecting velocity linetype in uvaver. Once, the uvsets have the identical frequency structure, Miriad task invert can synthesize an imaging line cube from multiple uvdata sets. Here is an exmaple of the usage:
uvaver vis=n7538.h30a_1 line=velocity,320,-220,1 out=n7538.h30a_1.vel uvaver vis=n7538.h30a_2 line=velocity,320,-220,1 out=n7538.h30a_2.vel uvaver vis=n7538.h30a_3 line=velocity,320,-220,1 out=n7538.h30a_3.vel
Here n7538.h30a_1, n7538.h30a_2, n7538.h30a_3 are the calibrated single source files but the frequency structure differs from each other. The linetype: line=velocity,320,-220,1 selects the velocity domain for redoing the frequency grid, i.e. output channel number = 320, beginning channel in velocity=-220 km/s and channel width = 1 km/s. The output uv datasets n7538.h30a_1.vel, n7538.h30a_2.vel and n7538.h30a_3.vel are re-constructed to the same frequency structure and invert can make an image line cube synthesized from the three uvdata sets:
invert vis=n7538.h30a_1.vel,n7538.h30a_2.vel,n7538.h30a_2.vel \
map=n7538.h30a.map beam=n7538.h30a.beam \
imsize=256,256 cell=0.2 sup=0 \
line=channel,36,100,5
The linetype: line=channel,36,100,5 set in invert
is to produce
36 line image panels starting from the 100th channel with a line width
averaged down to 5 km/s.