James, I was poking fun at you. I think you meant your error was less than 1%, not your accuracy. :-)
Mark On Thu, Feb 10, 2022 at 6:20 PM Reddell, James R < jreddell.ca...@austin.utexas.edu> wrote: > I may be in error, and they may have been better than that. > That was a very long time ago. > > James > ------------------------------ > *From:* Texascavers <texascavers-boun...@texascavers.com> on behalf of > Mark Minton <mamintonca...@gmail.com> > *Sent:* Thursday, February 10, 2022 5:17 PM > *To:* texascavers@texascavers.com <texascavers@texascavers.com> > *Subject:* Re: [Texascavers] Brunton Revisited > > If your accuracy was less than 1%, I think you had a problem! ;-) > > Brunton accuracy was pretty good, but you can't beat properly calibrated > Disto-X2s with front and backsights. I've done several surveys with less > than 0.5% loop-closure error, and a couple of large loops (over 2000 feet) > had 0.1% error! > > Mark Minton > > On Thu, Feb 10, 2022 at 5:58 PM Reddell, James R < > jreddell.ca...@austin.utexas.edu> wrote: > > I mapped all of Caverns of Sonora up to the pit with a > Brunton on a tripod and we consistently got less than 1% > accuracy in short and long loops. I also got very good accuracy > in some long surveys in Yucatan caves. > > James > > ------------------------------ > *From:* Texascavers <texascavers-boun...@texascavers.com> on behalf of > speodes...@gmail.com <speodes...@gmail.com> > *Sent:* Thursday, February 10, 2022 4:40 PM > *To:* texascavers@texascavers.com <texascavers@texascavers.com> > *Subject:* Re: [Texascavers] Brunton Revisited > > Thanks for leveling with us, Dwight. > > Doing the inclinations was hard going handheld. All I ever owned were two > Army Bruntons. Suuntos were a big change! > > And thanks to Carl for his good article. > > William R. (Bill) Elliott > Sent from my iPhone > > On Feb 10, 2022, at 4:34 PM, Dwight Deal <dirt...@comcast.net> wrote: > > Carl Kunath wrote an excellent historical article on the use of the old > Brunton compass in cave surveying. Unfortunately, the major source of > error was not clearly noted. > > That error is not having the Brunton as near perfectly level as possible > when you make the sighting. A tripod helps if you pay attention, but it is > possible to make accurate sights hand-held as well. > > I taught Herb Conn how to survey with a Brunton in 1959, and in many miles > of hand-held Jewel Cave survey loops our error was consistently on the > order of ½ of 1%. Keeping it level was the key. Considerable contortions > were sometimes required of the surveyor, however. > > DirtDoc > >
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