Re: [Therion] Detecting errors
An error of 3 degrees in clino does indicate a device out of calibration. I would expect it to be within 0.5 degrees for a well calibrated device, and would not tolerate more than 1 degree. In my experience poor calibration is usually down to either just inaccurate calibration shots, or local magnetic anomalies: take off watch, step counter, metal belt buckle, jewellery, glasses, helmet, lights, steel toe caps, etc!! Sent from my iPhone > On 5 Sep 2019, at 12:10, Max D wrote: > > So I know that if the display is to the right the Disto tends to reassure an > Azimuth 2 degrees to high and if the display is to the left. > And when the display is to the left it tends to give an Azimuth 1 degree to > low. > > But perhaps I just should try to do more and better calibrations instead of > fixing stuff afterwards. ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Re: [Therion] Detecting errors
You could also indicate the misalignment with instrument correction commands, but i dont know the exact command at the moment. I think that would not with different orientations of the same device... > Am 05.09.2019 um 13:10 schrieb Max D : > > > >> On 5. Sep 2019, at 08:28, Olly Betts wrote: >> >>> On Fri, Aug 16, 2019 at 05:11:22AM +0200, MD wrote: >>> We also then to measure the same small loop at the beginning of each trip: >>> A-B in four device orientations >>> B-A in four device orientations >>> A-C in four device orientations >>> C-A in four device orientations >>> C-B once >>> >>> So I could calculate an SD based on that. >> >> You probably don't want to work out a set of SDs per-trip - > > Currently we set the SD per calibration - which works out to about every > second trip. We Take the "Error stddev" from Topodroid Calibration Results - > e.g.0.1058 in the attached Screenshot. > > Thinking of it, this might be the wrong approach because it only considers > the instrument. > >> *sd tape 0.002 metres ; 2 millimetres >> *sd compass clino 0.5 degrees >> *sd position 0.05 metres ; 5 centimetres > > Interesting. I will read up on the difference between tape and position > >>> For sone Devices errors seem to be bound very much to orientation. In >>> the data saved by TopoDroid you can see the device orientation and so >>> we could set a sd based on the direction in which the shot was taken. >>> I have nit investigated this further so far. Also because we have this >>> data only for about 20% of the cave. >> >> This is already taken into account - you tell Survex the SD for the >> "tape" (read laser range-finder), "compass" and "clino" (read magnetic >> field measuring devices) and position (how close to the station you >> actually measure from) and it uses the direction of the leg to produce >> a 3D set of expected errors, which are then summed along each traverse. > > But I would need a extra set SD data per device orientation. > So I know that if the display is to the right the Disto tends to reassure an > Azimuth 2 degrees to high and if the display is to the left. > And when the display is to the left it tends to give an Azimuth 1 degree to > low. > > But perhaps I just should try to do more and better calibrations instead of > fixing stuff afterwards. > > >>> TopoDroid also is able to flag an “magnetic anomaly” - i’m not totally >>> sure how but this als could be used in setting a per shot SD. i have >>> not looked much into this. >> >> I think you want to treat that as an in-cave indication that you should >> check for sources of magnetic interference and redo affected readings. > > Good Advice! > > Thanks! > > --max > > > ___ > Therion mailing list > Therion@speleo.sk > https://mailman.speleo.sk/listinfo/therion ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Re: [Therion] Detecting errors
> On 5. Sep 2019, at 08:28, Olly Betts wrote: > >> On Fri, Aug 16, 2019 at 05:11:22AM +0200, MD wrote: >> We also then to measure the same small loop at the beginning of each trip: >> A-B in four device orientations >> B-A in four device orientations >> A-C in four device orientations >> C-A in four device orientations >> C-B once >> >> So I could calculate an SD based on that. > > You probably don't want to work out a set of SDs per-trip - Currently we set the SD per calibration - which works out to about every second trip. We Take the "Error stddev" from Topodroid Calibration Results - e.g.0.1058 in the attached Screenshot. Thinking of it, this might be the wrong approach because it only considers the instrument. > *sd tape 0.002 metres ; 2 millimetres > *sd compass clino 0.5 degrees > *sd position 0.05 metres ; 5 centimetres Interesting. I will read up on the difference between tape and position >> For sone Devices errors seem to be bound very much to orientation. In >> the data saved by TopoDroid you can see the device orientation and so >> we could set a sd based on the direction in which the shot was taken. >> I have nit investigated this further so far. Also because we have this >> data only for about 20% of the cave. > > This is already taken into account - you tell Survex the SD for the > "tape" (read laser range-finder), "compass" and "clino" (read magnetic > field measuring devices) and position (how close to the station you > actually measure from) and it uses the direction of the leg to produce > a 3D set of expected errors, which are then summed along each traverse. But I would need a extra set SD data per device orientation. So I know that if the display is to the right the Disto tends to reassure an Azimuth 2 degrees to high and if the display is to the left. And when the display is to the left it tends to give an Azimuth 1 degree to low. But perhaps I just should try to do more and better calibrations instead of fixing stuff afterwards. >> TopoDroid also is able to flag an “magnetic anomaly” - i’m not totally >> sure how but this als could be used in setting a per shot SD. i have >> not looked much into this. > > I think you want to treat that as an in-cave indication that you should > check for sources of magnetic interference and redo affected readings. Good Advice! Thanks! --max ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
