Here's a way to do it in aips++:
> Hi Tim > > There must be some way to do this in aips++, but I haven't spotted it ... > > I can see how to read in an image from a FITS file and FFT the image > to the UV domain. > > I then want to degrid the image from the FFT grid on to the UV tracks > defined in an MS. I haven't been able to spot an appropriate > method in the imager or image tools to do this.
imager.ft or newsimulator.predict will do this. The degridded visibilities will be put in the MODEL_DATA column.
Cheers,
Tim
Here's a way to do it in MeqTrees:
In MeqTrees we read in the image via a FITSImage node. We then FFT it with a FFTBrick node. Finally we interpolate to visibilities with a UVInterpolWave or UVInterpol node. NOTE: MeqTrees is very finickly about what constitutes a valid FITS file - we need the four axes defined with (usually) CTYPE4 == FREQ, CTYPE3 Stokes or Time, CTYPE2 L, or Dec, and CTYPE1 RA or M, where for example we might have:
AXIS = 4 / number of array dimensions NAXIS1 = 101 NAXIS2 = 101 NAXIS3 = 1 NAXIS4 = 4
Here we have four frequency images, each of size 101 x 101.