That makes it sound as if Eddie could be 100 metres from the deposition site and still alert. It seems to depend on where he picks up the scent in the air not the location of the deposit.
Very much a blunt instrument as opposed to a precision tool then which is fine if there is actually something there to be found as the source and the location will be immediately obvious.
In a more esoteric situation when there is nothing there to be found and where there may never have been anything there to be found ... the importance of the exact point of reference is critical in my opinion.
When there is an indication but there nothing visible to prompt that indication ... Martin Grime is on record on numerous occasions including his report on Jersey, as stating that dog indications must be backed up by forensics.
Misty has noted that even in the close confines of the sofa and around it there is absolutely no way of knowing exactly why Eddie was barking.
I don't think second guessing a dog is a great idea ... particularly if it results in flawed conclusions which are specifically contrary to the professional advice given by the dog's handler.