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derekbristol wrote:I don't think there's anything fundamentally wrong with the equipment. I've been told it's the same mag and accel sensors as the DistoX. Most people seem to agree that it's capable of giving both good azimuth and inclination readings, but there seems to be a bug in the latest firmware (which isn't all that late). Lynn Brucker did a lot of work with the DUSI and posted the results here:
http://www.forums.caves.org/viewtopic.p ... hilit=dusi
Lynn believes the older firmware worked pretty well and then an update (I think in May '09) screwed things up. If you search the forum archives for "DUSI" you'll get some more background, but not a lot of answers to help solve your current predicament.
Again, my unit is version 2, but from the main menu I select "6", which is calibration. In the next menu I select 2, 3 and 4, which are accelerometer, magnetometer and LASER alignment respectively. I then just follow the instructions to calibrate each. I believe version 1 menus are different so this may not help.
I've sent you a CD with all the files I have on the DUSI as well as some articles Lynn wrote on calibration of digital survey instruments. There's also a presentation given at the 2008 convention on digital survey. All good reading.
derekbristol wrote:Once I have the 18 or so stillpoints I just press "1" to calibrate. It calculates some constants (in units of %). That's where my understanding ends. I assume it uses these constants to convert whatever voltage or current reading it gets from the accelerometer or magnetometer into a corrected inclination angle or azimuth respectively. I'm not sure if it's important to do the calibration in a specific order or not. I've generally done accelerometer followed by magnetometer and lastly LASER alignment.
I've suspected that some of the problem with the magnetometer calibration has to do with sensitivity. The readings change very quickly and there appears to be a lot of noise. If your hand shakes a little as you're getting the measurement then maybe there's a significant amount of noise captured in the reading. When Lynn did her work she used a non-magnetic tripod and clamp to hold the instruments. This might improve the repeatability of the measurement.
I'm not much of an electronics or software guy, so I'm not going to be much help solving these issues. I'm pretty good with statistics and characterizing measurement systems, so I know how to handle the data.
Good luck and let the forum know if you develop a solution. There are a number of frustrated DUSI owners out there.
derekbristol wrote:Sounds like turning the autocal off might be a good idea. I don't think mine has that function.
I believe Lynn Brucker has recommended running calibrations on digital survey instruments about every 30 days. In another thread someone with a DistoX was doing it before every survey. Based on Lynn's suggestion I would expect the calibration and therefore readings to be reasonably stable for up to 30 days. If you are getting very different results from day to day then there's probably something else going on.
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