survey accuracy

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survey accuracy

Postby bobby49 » Oct 5, 2018 6:06 pm

When surveying a cave, we try to get the best accuracy that is easily obtainable. But, what is obtainable, and at what cost of time or money? How good can you get?

It has been stated that for azimuths, front sight - back sights should agree to 2 degrees or better. I don't know the standard for tilt or slope distance. Of the three dimensions (distance, tilt, azimuth) which one has the most need for accuracy? I would think that distance is, at least in a horizontal cave. It seems as though the vertical caves that I've been in aren't vertical enough. I would think that tilt angle needs the least accuracy. I mean, if a passageway tilts by 20 degrees and then changes to 35 degrees, that means something. But if a passageway tilts by 20 degrees and then changes by 2%, that means almost nothing. I'm just thinking ahead toward loop closure.
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Re: survey accuracy

Postby GroundquestMSA » Oct 6, 2018 7:53 pm

Cave maps do not need to be super accurate. They are a rough and sometimes artistic representation/interpretation and fulfill almost all of their practical uses even when significantly inaccurate. Loop closure is usually unimportant.

It is pretty easy to be accurate though. Last week we did a 2-man blitz survey of over 500' of virgin cave. No backsights. Our loop was only 400 feet long but took 27 shots. We were dead on in elevation and 1.5' from perfect closure. Avoiding the major blunders and having a good sketcher equals a fast, cheap, and simple survey that will be accurate enough for all but very specialized and rare applications.
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