code: def latLongGridPredicate(field, digits=1):
      
      if any(field):
          return (str([round(dim, digits) for dim in field]),)
      else:
          return ()
docs: Given a lat / long pair, return the grid coordinates at the
      nearest base value.  e.g., (42.3, -5.4) returns a grid at 0.1
      degree resolution of 0.1 degrees of latitude ~ 7km, so this is
      effectively a 14km lat grid.  This is imprecise for longitude,
      since 1 degree of longitude is 0km at the poles, and up to 111km
      at the equator. But it should be reasonably precise given some
      prior logical block (e.g., country).