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<mailto: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<mailto:texascavers-boun...@texascavers.com>> on behalf of speodes...@gmail.com<mailto:speodes...@gmail.com> <speodes...@gmail.com<mailto:speodes...@gmail.com>> Sent: Thursday, February 10, 2022 4:40 PM To: texascavers@texascavers.com<mailto:texascavers@texascavers.com> <texascavers@texascavers.com<mailto: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<mailto: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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