So Mark, can you update previous X2 conversions? We use a Brunton/Suunto compass course at Fort Stanton which has a center point with 6 radial points ~ 50 feet away. We have extra sockets near one of the radial points just 4 feet away for the +\- 45 degree inclination shots. We use the 50 foot points for the Az compass shots, and multiple calibrations can be done at the same time, usually at dusk.
At home, I reduced this to three posts 15-20 apart, and two more 4 feet away. See attached sketch. - Pete
FSCSP Disto Cal Course.pdf
Description: Adobe PDF document
On Jul 23, 2019, at 2:30 PM, mmin...@caver.net wrote: On most expeditions I've been on, Distos are calibrated, or at least checked, on site. At Carlsbad Caverns a couple of years ago, we calibrated the Distos _in_ the cave at the beginning of survey. We got great backsight agreement and awesome closures. One very large loop closed with under a foot of error. We've had similar closure success in Warm River Cave, where we closed a 2300-foot loop with 0.1% error. Of course if the data are good, large loops should close better than small ones because minor random errors will tend to cancel out. Not so for systematic errors like from miscalibrated instruments. The current DistoX2 firmware has a feature that compares the last three shots and if they agree to within 2 degrees (or whatever), the instrument beeps and displays three dots. That way you know whether your shots are good without having to look back and compare manually. If you rotate the unit between shots it uses different sensors, and is good for catching calibration errors. Of course taking actual backsights is still advisable because that's the only way to detect possible magnetic anomalies. In actual practice we find that if treated well, the DistoX2 generally stays within calibration over long periods of time and from one place to another, within reason. Mark Minton On 2019-07-23 14:07, Pete Lindsley wrote: > DIsto X2s are great in a cave when they are calibrated. I have > modified 6 units so far with 2 more on the bench. One of those I > suspect has a bad daughterboard. I found out the other Disto had an > issue before I took it apart. It helps to calibrate the units before > going into a cave. At Stanton we have found bad calibrations both > during a survey or afterwards. Ditto for Bruntons & Suuntos. So you > need to be able to calibrate the DIsto X2 in the cave, which means you > need to carry in your Android phone or tablet. (The Brunton is more > rugged than those smart devices, and may be a worthy backup unit.) > All of the Suuntos I have bought have only lasted for 3-4 years before > you have to replace the clouded up “smart part”, at just slightly > less cost than a brand new Suunto. The Suuntos can also have compass & > inclination errors (like Disto & Bruntons) but few people bother to > check calibration. At least the Suuntos are waterproof. Suuntos & > Bruntons work well in the daylight, not so much the Distos. > For the Disto units where the laser does not align with the sides of > the unit, you certainly need to carefully run a calibration that > rotates the unit on all 4 sides. Some of the calibration videos out > there don’t do that. > I started off with a used tripod-mounted quadrant Brunton using the > Shadow Method. We ran the closure data in Carlsbad against Tom > Rohr’s theodolite and precision level survey using the > Hardy-Corcoran Fortran program on an IBM 360. Overkill for your > smaller caves, but we made pretty good FS/BS measurements out to ~ 100 > feet. Over the last 15+ years the Fort Stanton Snowy River surveys > have used all of these devices and our sketching techniques have > improved 200%, partially because it is so easy to use the Disto to > accurately shoot in the key sketched items. The Suuntos apparently > introduced blunders, and perhaps lazy FS/BS techniques, because some > of those older surveys appear to show that water runs uphill. > Our new trick is an Arduino controlled data logging barometer that we > hope will help sort out these past elevation errors. I am hoping we > can kill off some of our 20 foot elevation closure errors from old > Suunto surveys with the baro units quickly checking the route. When > your 12 mile long stream passage has an average inclination of ~0.2 > degrees, careful backsights become very important. It might even help > to mount your Disto-X2 on a tripod and take instrument height / light > height data like we were doing 50 years ago with the lowly Brunton. > Hand-held 200 foot Disto shots usually have quite a bit of > “wiggle” if you are trying for 0.5 degree precision. > - Pete _______________________________________________ Texascavers mailing list | http://texascavers.com Texascavers@texascavers.com | Archives: http://www.mail-archive.com/texascavers@texascavers.com/ http://lists.texascavers.com/listinfo/texascavers
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