For each measurement , we can estimate a minimum image size by finding the equivalent Gaussian that achieves the same quotient on the corresponding baselines . This criterion is motivated by the property that long baselines will tend to measure more flux density than extrapolated by the equivalent Gaussian on short baselines , reflecting small - scale power from image substructure . This criterion also makes the simplifying assumption that the source has isotropic size ; this assumption is both supported by our data ( see Section 3.2 ) and is not especially problematic because the ALMA - LMT and SMT - LMT baselines sample similar orientation angles ( see Figure 1 ) .