Tunnel length miscalculation

It was discussed a while back but I think the thread must have been deleted. But think how hard it was to estimate the distance from the fence to the woods then do it underground. They couldn't exactly run a tape measure across the ground after all, nor make it obvious that they were trying to work out the distance. Not easy just to do it by eye, but that was the only way. I would agree with you regarding the roots- if they'd actually come out under the trees the chances are they wouldn't have been able to dig upwards without hitting roots or tree trunks. They cdould have cut their way through to some extent but that would have been near impossible IMO. I personally think they wanted to be near the treeline but not under the trees myself.

"Oh dear. How sad. Never mind!"

The method they most likely used to calculate the distance was triangulation, since it would have been impossible to take a direct measurement of the distance, even if Hilts was outside the wire. It would take too long to explain the technique here, you can look it up if you are interested.

It can be done with a high degree of accuracy using simple tools they could have made themselves. If you do it right, there is no need to directly measure. Ships use it all the time to determine distances from their location.

Cavendish screwed up, or didn't allow for enough of a cushion in the calculations to account for inherent sources of error.

Also, most tree roots tend to spread outward more than downward, so if they were say 10-15 feet down, they'd very likely not see very many roots until they started digging upward. Bear in mind also that the no-man's-land between the fence and the woods may very well have had trees on it that were clear cut back when the camp was built. So they might have been encountering random tree roots as they dug all the way out.

For one thing, they would have encountered roots all along the way if they encountered roots at all. The camp wasn't built in an open spot in the forest, but in the middle of the forest that had been cleared of trees. And yes, they did miscalculate the distance. They had to eyeball the distance and they were off by about six feet over the 330 foot length of the tunnel. The character of Hilts is a fabrication, nobody ever escaped and allowed themselves to be captured.

This will be the high point of my day; it's all downhill from here.

They couldn't have gotten EVERYONE out because not everyone had papers. Many of the prisoners (including Paul Brickhill, the author of the book) never intended to try to get out.

The miscalculation also didn't have that much to do with the way the prisoners were recaptured.

I know this post already has a # of replies and I preface mine with saying I am not a surveyor nor have ever had need to build a tunnel nor escape from an type of prison..but given that almost everybody agrees the miscalculation in length of the tunnel was a big error resulting in the failure of many people getting out and those who did were delayed in doing so..why did the tunnel makers..not check on the exit point the night before the escape?..I realize there may have been some risk..but it seems to me to be minimal..to devise a small observation hole to verify the exit..so, the finalization of plans could occur..i realize at that point how a delay may not have worked with the timeline of documents prepared but there would not have been the surprise and disappointment to deal with the night of the escape..they could have planned on what needed to be done as far as signals..they may have decided on fewer people getting out as it was going to take longer..they could have warned all those in line only to come when signaled so maybe that individual would not have chosen to exit when he did and was discovered..there were a number of things that could have been figured on in last minute prearations had they known beforehand and in addition, they would have loosened the exit area..which I read also contributed to the delay in exiting..Has anybody ever questioned this and what would be the downside besides a small risk of discovery..at least in my opinion, a small risk..

With all the questions here asking "how could they come up short?" the assumption seems to be that the tunnel was constructed perfectly perpendicular to the tree line. A little right-triangle trigonometry shows that a 300' tunnel would be 20' shy of the tree line if the constructors were 21 degrees off in their direction. Not exactly inconceivable. You try going 30 feet underground and then beginning your horizontal dig without making an error like that. I doubt your compass would work very well down there.

One thing to remember is that a tunnel had already been discovered and they were rushing to get the one tunnel dug. I remember reading about an interview were a German guard at Stalag Luft 3 said that they suspected the prisoners were digging a tunnel but didn't exactly know where. I think the the prisoners realized the window of opportunity to escape was closing and they had to make a move.

If you remember what Bartlett said what goal was of the prison escape. It wasn't to get everyone out but to cause such a disturbance that the Germans would have to pull soldiers from the frontlines and to try and recapture them.

Just watched it again, that must be at least 15 times.
I, too, have always been puzzled by the miscalculation of the exit point. The prisoners were air crew, including pilots and navigators, all of who were expected to be good mathematicians and geometry is basic stuff to them. They didn’t need tape measures as they could easily set any measuring scale on the surface that could be transferred underground.
I also think it was unlikely they relied on a single bloke to do the calculations without it being checked and double checked by other able scrutinisers, so laying the blame on one bloke is, I feel, quite unfair.
The sad fact is that we’ll never know the truth of it - but that doesn’t matter. I was certainly one of the best films of all time - in fact it is timeless.