Third Generation Disto-X Progress

Techniques, equipment and issues. Also visit the NSS Survey & Cartography Section.

Moderator: Moderators

Re: Third Generation Disto-X Progress

Postby Extremeophile » Feb 18, 2014 10:36 am

LWB wrote:Is your delta of 0.28 typical of what you got during calibration?

Actually, that's the best calibration I've had. The first was 0.55, the worst has been 0.65 (done in-cave), and the current is 0.46. However, even with the delta=0.65 we were generally getting FS/BS azimuth agreement to within 1 degree. The clino agreement is always within ~0.1 degrees regardless of the delta.

I've mostly been calibrating in an open area (greenbelt) that's a couple minutes walk from my front door. There are houses nearby, but I think it's clear enough to not have interference. I tried in my back yard, but there are buried cables or something that seem to be a problem, even for a Suunto. I've calibrated a few times in a cave, but haven't seen much difference from calibrating in the greenbelt.

The instructions suggest letting the reading stabilize before collecting a calibration point, but the LCD only displays CAL and the data point, so it's hard to know when it's stable. I do run through the measurements pretty quickly. I'm careful with the first 16 readings, but not so much with the remaining readings, and I don't aim at a target for readings 17-56. I've thought about deliberately going slower with those secondary readings to see if it influences the delta value.
User avatar
Extremeophile
NSS Hall Of Fame Poster
 
Posts: 761
Joined: Dec 7, 2009 7:37 pm
Location: Littleton, CO
Name: Derek Bristol
NSS #: 34941
Primary Grotto Affiliation: Colorado Grotto
  

Re: Third Generation Disto-X Progress

Postby LWB » Feb 18, 2014 1:18 pm

I've learned to slow down on taking calibration shots. I try to let the laser be on the calibration target for 3 seconds before pushing the button. With the first generation there was a slight delay or sometimes a couple second delay before it beeped and the laser went out. The X2 seems to respond instantly, which was a bit disconcerting. I tried holding the button down, but it the response is still very fast.

The weird thing was that in both cases the deltas on the first 16 measurements (the level stations) were significantly higher than the subsequent ones. Did you see that also?

If you export the calibration file to a text file it will give you the calibration matrix. I'm curious as to what values you are seeing there.

My in cave test course as well as the compass test course I do 3 readings in each orientation. The readings in a given orientation were very repeatable. More variation between orientations (1.0 degree on FS, 0.6 on backsight).
LWB
Prolific Poster
 
Posts: 117
Joined: Oct 29, 2007 7:36 pm
  

Re: Third Generation Disto-X Progress

Postby Martin Sluka » Feb 18, 2014 2:17 pm

LWB wrote:I've learned to slow down on taking calibration shots. I try to let the laser be on the calibration target for 3 seconds before pushing the button. With the first generation there was a slight delay or sometimes a couple second delay before it beeped and the laser went out. The X2 seems to respond instantly, which was a bit disconcerting. I tried holding the button down, but it the response is still very fast.

Please, try to use timer button. :doh:
User avatar
Martin Sluka
NSS Hall Of Fame Poster
 
Posts: 380
Joined: Mar 17, 2006 11:28 am
Location: Prague, Czech Republic
Name: Martin Sluka
NSS #: 29010
  

Re: Third Generation Disto-X Progress

Postby Extremeophile » Feb 18, 2014 3:25 pm

Martin Sluka wrote:Please, try to use timer button. :doh:

My experience is the same as Lynn's, i.e. during calibration the measurement is taken immediately upon pressing the button, unlike standard measurements where there is a slight delay. Not sure if the timer function works in calibration mode, but I'll give it a try.

For azimuth repeatability I get roughly the following variation:
Measurements in the same direction in the same instrument orientation - 0.1 degrees
Measurements in the same direction with various instrument orientations - 0.1-0.3 degrees
Measurements in opposite directions (FS/BS) with the same instrument orientation - 0.1-0.2 degrees
Measurements in opposite directions with various instrument orientations (worst case) - 0.3-0.5 degrees

Inclinations are generally repeatable to within 0.1 degrees regardless of direction or instrument orientation.
I haven't noticed much difference in the repeatability regardless of the delta values I've been getting during calibration.
These values are taken on a test course. The variation observed during actual surveys are a bit greater, but then there is a long list of small special cause sources of error.

The repeatability is basically a gauge of precision, but doesn't tell you anything about accuracy. I was asked about how to verify accuracy at Carlsbad Caverns last weekend. We did a few back sights with a Suunto and got readings within 1 degree, but I'm curious how others approach this question. I know Mammoth Cave has a calibration course that deals with this, but I recall reading a paper somewhere that suggested accuracy varied following a sine function, i.e. it was completely accurate at two points of the compass, and had maximum error 90 degrees from this orientation. If this is true then a single aspect calibration course may not be the best check on accuracy.
User avatar
Extremeophile
NSS Hall Of Fame Poster
 
Posts: 761
Joined: Dec 7, 2009 7:37 pm
Location: Littleton, CO
Name: Derek Bristol
NSS #: 34941
Primary Grotto Affiliation: Colorado Grotto
  

Re: Third Generation Disto-X Progress

Postby Extremeophile » Feb 19, 2014 8:33 am

The dot plots below show the front/back sight errors during a recent survey. There are many potential sources of error during an actual survey that will increase the variation observed on a controlled calibration course. The average difference for azimuth readings is 0.6 degrees, and for inclination readings it is 0.4 degrees. The data was collected over 2 days with 2 different instrument people, so it represents a combination of repeatability and reproducibility error and gives you a good idea of the real world results you might expect.

These 2 days of survey included 121 survey shots, but we don't do back sights on terminal shots, so there are FS/BS comparisons for 103 shots. This survey would be considered some of the worst imaginable with traditional Suuntos. We surveyed through tight contorted breakdown and in steep, complex 3D phreatic maze passage. This would have required many repeat measurements if we had used Suuntos, and we wouldn't have been nearly as productive. In some cases stations were set on ceilings or floors where reading Suuntos would have been difficult to impossible. The flexibility in station setting location also reduces the total number of stations that need to be set.

Although the simplicity of pressing a button, and the convenience of wireless transmission and recording of data eliminate a number of types of traditional survey blunders, I still feel it is necessary to collect front and back sights. It is possible that the wrong target may be shot, or it is possible that a headlamp or vertical gear could bias the azimuth reading. There are cases where doing multiple front sights may just repeat the same blunder, so a high quality survey should continue to include back sights.


Image

Image
User avatar
Extremeophile
NSS Hall Of Fame Poster
 
Posts: 761
Joined: Dec 7, 2009 7:37 pm
Location: Littleton, CO
Name: Derek Bristol
NSS #: 34941
Primary Grotto Affiliation: Colorado Grotto
  

Re: Third Generation Disto-X Progress

Postby LWB » Feb 19, 2014 12:04 pm

I agree that it is very important to do backsights with the Disto X (with the same instrument). Including Distance which can be a huge error source. But with the first generation Disto X (A3s) the first sign that the battery was running low was that FS/BS azimuth errors got large. This would happen before the low battery indicator showed anything but a full charge. :sad:

FS/BS errors are the sign that something is wrong with the calibration. Never use a Disto X without doing backsights! :doh:
LWB
Prolific Poster
 
Posts: 117
Joined: Oct 29, 2007 7:36 pm
  

Re: Third Generation Disto-X Progress

Postby Tony C » Mar 19, 2014 8:17 pm

I converted my new E7400 to a DistoX last week. When I first powered it up, I expected the azimuth numbers to act roughly like a compass when I spun the laser around the room, but they did not. Very very, non-linear, it took great efforts to find a zero reading (north) -- and it was not close to north! That seemed odd to me, but it wasn't calibrated yet, so I didn't worry too much.

So I went into the woods and calibrated it, or did my best. After multiple attempts, the best I got it to was 0.58. But at least I could spin around the azimuths read like a compass. I took it to the fieldstation, and had my buddy Zeb from Harrisonburg, a long time DistoX owner, calibrate it. He didn't get it any better. But we tried it mine out in-cave, using it for backsights, and they agreed with Zeb's DistoX foresights within 2 degrees, so I said good enough.

Not completely satisfied, today I read this thread, and took my DistoX apart to measure all the screws so I could buy non-steel replacements.

As I disassembled it, I carefully put all the screws into a little parts holder so I wouldn't lose them. I put it back together, and again the azimuth reading was very non-linear as I spun around the room. And no matter how I tried, I could never get it to read zero (north.) Huh. What changed?

Well, here's a photo of my parts holder.

Image

That is a MAGNETIC parts holder. I had turned all the steel case screws into little magnets! Doh!

I could take one screw out, and a compass needle would follow it all the way around the compass.

I had an old tape head demagnetizer around, so I demagnetized all the screws. After demagnetizing, a screw would only slightly deflect the compass needle, and the needle would not follow the screw all the way around. After demagnetizing all the screws, the azimuths read like a compass. I'll get out this weekend to calibrate it and see how good I can get it.

Tony.
44230
Tony C
Infrequent Poster
 
Posts: 11
Joined: Sep 24, 2011 6:43 pm
NSS #: 44230
Primary Grotto Affiliation: Philly
  

Re: Third Generation Disto-X Progress

Postby LWB » Mar 20, 2014 2:11 pm

When we finally replaced ALL the screws in the A3 Disto Xs with brass or stainless (beware, not all stainless is non-magnetic) we got significantly better results. Unfortunately the E7400 doesn't use the same size screws. Still trying to source some for the E7400.

Additionally the pin and the spring in the flip out holder were steel in previous model, and I suspect they are in the E7400 as well. The risk of any steel parts becoming magnetized is more than I want to take.

I did another calibration this month. Still seeing delta's of around 0.45. And the individual deltas are much higher on the first 16 (level) readings. Like Derek, the repeatability in a given orientation is excellent - better than the A3s (if a delta is not at least 0.22 or below, it will not pass the compass test course or be consistent). I took a complete set of theodolite comparison data. Spread is fully + and - one degree. And the sinusoidal swing in the error plots is obvious. If you pick the right angle the error is nearly zero, the wrong angle and it is 2 degrees. It did pass the (single angle) compass test course, but 2 of the 3 A3 Disto Xs I calibrated performed better. Only the A3s went into the cave.

I need to removed the pin and spring and get those screws replaced. I'm hoping that does the trick. Be nice to replace with brass, but I really have no need of that bracket.
LWB
Prolific Poster
 
Posts: 117
Joined: Oct 29, 2007 7:36 pm
  

Re: Third Generation Disto-X Progress

Postby lleblanc » Mar 20, 2014 2:19 pm

LWB wrote:When we finally replaced ALL the screws in the A3 Disto Xs with brass or stainless (beware, not all stainless is non-magnetic) we got significantly better results.


Also be aware that some brass screws are actually brass-plated steel, thus magnetic :(
User avatar
lleblanc
Frequent Poster
 
Posts: 85
Joined: Aug 10, 2007 2:19 pm
Name: Luc Le Blanc
  

Re: Third Generation Disto-X Progress

Postby LWB » Mar 20, 2014 3:54 pm

I noticed on the McMaster-Carr website it indicated that all the stainless steel screws were "magnetic" or "mildly magnetic". I find the hardware store SS is often non-magnetic if it doesn't have threads (e.g. S hooks), but the threaded stuff is all slightly magnetic.

The exact replacement of one kind of screw (for the E7400) only comes in steel and stainless steel. Argh!

McMaster-Carr does have a decent selection of metric brass (in quantities of 50 or 100). Which is not so easily found in the tiny sizes in the USA.
LWB
Prolific Poster
 
Posts: 117
Joined: Oct 29, 2007 7:36 pm
  

Re: Third Generation Disto-X Progress

Postby caver.adam » Mar 21, 2014 8:26 am

Higher quality steel is less/non magnetic. Cheaper steel is always magnetic.
User avatar
caver.adam
NSS Hall Of Fame Poster
 
Posts: 345
Joined: Feb 8, 2012 12:26 pm
Primary Grotto Affiliation: Louisville Grotto
  

Re: Third Generation Disto-X Progress

Postby LWB » Mar 26, 2014 9:47 pm

Finally tackling the removal of as much steel as possible from the E7400X - the pins holding the flip out bracket are not magnetic, so they must be stainless - but they are gone now. The two springs are magnetic and embedded in one of the sides of the black plastic bracket where the pins goes through is a piece of steel (a stop?).

Have brass replacements for all the screws now also. Very interested in seeing if this will improve the delta on the calibration.
LWB
Prolific Poster
 
Posts: 117
Joined: Oct 29, 2007 7:36 pm
  

Re: Third Generation Disto-X Progress

Postby Extremeophile » Mar 27, 2014 9:20 am

LWB wrote:Have brass replacements for all the screws now also.

I assume you're referring to the case screws. Do you have a source? Also, are you removing additional parts inside the case that are not specified in the installation instructions?
User avatar
Extremeophile
NSS Hall Of Fame Poster
 
Posts: 761
Joined: Dec 7, 2009 7:37 pm
Location: Littleton, CO
Name: Derek Bristol
NSS #: 34941
Primary Grotto Affiliation: Colorado Grotto
  

Re: Third Generation Disto-X Progress

Postby Martin Sluka » Mar 27, 2014 10:44 am

Extremeophile wrote:I assume you're referring to the case screws. Do you have a source? Also, are you removing additional parts inside the case that are not specified in the installation instructions?


http://www.japanesescrews.com/contact.html
User avatar
Martin Sluka
NSS Hall Of Fame Poster
 
Posts: 380
Joined: Mar 17, 2006 11:28 am
Location: Prague, Czech Republic
Name: Martin Sluka
NSS #: 29010
  

Re: Third Generation Disto-X Progress

Postby Martin Sluka » Mar 27, 2014 10:50 am

Don't forget, there is a big metalic piece as former contact for batteries. You may replace it in this way:

Image Image Image Image Image
User avatar
Martin Sluka
NSS Hall Of Fame Poster
 
Posts: 380
Joined: Mar 17, 2006 11:28 am
Location: Prague, Czech Republic
Name: Martin Sluka
NSS #: 29010
  

PreviousNext

Return to Survey and Cartography Forum

Who is online

Users browsing this forum: No registered users

cron