The three methods outlined above all cross-equalized the two surveys well. However, they all worked by effectively low-pass filtering the monitor survey to the bandwidth of the baseline survey. This is a safe strategy as there is no danger from noise blowing-up. An interesting question is whether it is possible to use the information contained in the high frequency survey to boost the bandwidth of the lower frequency survey. This is similar to deconvolution, and is very dangerous because there is always the danger of amplifying noise.