The best analogy I can give is when I'm offshore fishing, a matter of less than a mile can be the difference between a 500+ lb tuna trip and 0 lb tuna trip.
That's why we use ocean temp, weed line formation, current flow, contour lines (depth), TD loran points, VHF, GPS and an ongoing record (Bible sort to speak) of prior trips.
IMO, in a similar approach Hemi is utilizing the same logic and approach to the Silvey Hemi-1 relative to information, data and records available in this given area.