Shetland Attack Pony

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Dave H

Guest
biffa said:
cap 'n chris said:
Biffa's link leads to the fabled and dizzying land of Ubergeekdom. I visited it for a while but my eyes glazed over and my brain squealed while becoming gently frazzled.

I'm back in good old Numptyland now. Phew! 

Geeks rule.  Ha ha I squealed his brain.

I designed and built an electronic compass, yaw, roll and pitch sensor head using PICs and similar sensors (and a few more) around 1998/9 which fed into a sophisticated micro that actually crunched the numbers (which I didn't program). The application was for light aircraft and we only had to achieve an accuracy, resolution and repeatability of 1 degree in each axis. Accuracy and resolution were not a problem, but the repeatability over a wide range of conditions was the killer.
I would certainly say stick with measuring one plane of movement (such as the linked device) for an easier life! Having said that we did achieve the spec. with quite a bit to spare, but it really was prohibitively expensive for applications such as surveying (I think that the aircraft kit was being sold for $5000)  :eek:
If I ever had the time  :cautious: I'm sure that I could do something cheaper now, but I would want 0.5 degree specs. and for it to have a distance measuring laser pointer.

Up with the geeks! And yes, I am a rocket scientist (sort of)
 
M

Martin Melzer

Guest
beardedboy said:
Also a problem with these very purdy LED lights that are becoming more popular (Scurion, Stenlight, Nova, etc) is that they all use magnetic switches. With the SAP you can keep the device away from your head and the magnet and therefore keep accurate readings. Last time I talked to Phil he was also talking about the possibility of making the SAP beep when it detected a large change in magnetic field, but this isn't confirmed yet.

Scurion does not use a magnetic switch!
I have developed a compass/clino module myself (see my Auriga project - http://www.melzer.ch/html/aurigaimport.html) and I know how important it is to have no magnetic parts nearby.
For Scurion, we ran a finite element magnetic field simulation and found out, that using currently available magnetic field sensors, it is not possible to use magnets that are weak enough in order not to disturb the compass (I used a limit of 1% field disturbance in 10 cm distance). For that reason, we have the reletively complicated mechanical solution. Few swiss cavers would have bought the lamp if they would know that it ruins their surveying accuracy.

- martin
 

menacer

Active member
Borrowed one the other day for a little Mendip project i'd been promising to do for some time.Also had a disto.
It was a pleasure not to have to contort myself into funny position just to take a reading. Also there was no extra faffing with lighting the instrument just to take a reading.
Another good point, you can train it ahead to the area of the next survey station and see if youve got a good line of sight. (If you can see the red dot, you have)
Best of all, it is possibile to survey solo.
If one of the people surveying, cant fit through the squeeze or get up a climb the other can continue alone....
The downside of that is, Ive got no excuse to not return to all the bits of cave ive travelled alone, and remain unsurveyed....
Back to Draenan for this girlie....phhh

If anyone knows Phil and reads this, can you let him know I cant get the program to run in vista.(even with xp compatibility mode)
 

Chris J

Active member
Surveying Solo... obviously need a disto as no one to hold the tape measure - but a good advantage to this.
 

Cave_Troll

Active member
As long as you have a good base line, you can conduct a survey using just mag and dec, working in triangles, and then work out the distances using 3d trig.
 

Bob Smith

Member
Cave_Troll said:
As long as you have a good base line, you can conduct a survey using just mag and dec, working in triangles, and then work out the distances using 3d trig.

In theory that's great, but that's not really practical in most UK caves is it, fine if you are working with a sub minute instrument, with a stable setup, long survey legs etc, but it relies on intervisibilty of survey stations and it's an awful lot of hard work even for an experienced surveyor. A disto would be just fine and @ around ?125 a pop not too far out of reach either.
 

Rob

Well-known member
Chris J said:
Surveying Solo... obviously need a disto as no one to hold the tape measure...

Earlier this week i prooved this wrong. With a nicley sized rock to weigh down the end of the tape and a bit of thought about station possitioning it is possible.

However I was in a stupidly tight bit of passage though so would have been much nicer with a disto / friend.  :cautious:
 

graham

New member
Bob Smith said:
Cave_Troll said:
As long as you have a good base line, you can conduct a survey using just mag and dec, working in triangles, and then work out the distances using 3d trig.

In theory that's great, but that's not really practical in most UK caves is it, fine if you are working with a sub minute instrument, with a stable setup, long survey legs etc, but it relies on intervisibilty of survey stations and it's an awful lot of hard work even for an experienced surveyor. A disto would be just fine and @ around ?125 a pop not too far out of reach either.

For the truly obscure, I believe that Alfie Collins did the 1950s survey of Redcliffe caves using a plane table. I've used that method to draw surface features but can think of very few UK caves where it might be feasible.
 

menacer

Active member
Wow thanks for all that info guys...
So all I really needed was a slide rule, a protractor and a stick with a plumb line, a 6 inch ruler and a compass made out of  a bowl of water, a piece of cork, any magnet, and a needle.
Can anyone suggest a suitable parchment and quill for drawing it all up. :LOL:
Oh and dont forget the large rock...
 

CaversLass

New member
I was at a lecture recently where Trevor Faulkner recounted his one man method for surveying caves in Norway. Apparently he finds it is necessary when on expedition to Norway as he is normally on his own (obviously a billy no mates).  ;)

He was getting fairly good results though using a tape and a rock, also using a magnetic compass and clino.
 

ian mckenzie

New member
An article in The Canadian Caver #67 on Isla Madre de Dios mentions "the marriage betwen Auriga, a cave survey freeware for PDAs running under Palm OS, and Easytopo, an all-in-one topobox... Easytopo generates a laser ray to point towards the next survey station.  Then, pressing the one-touch button, length, azimuth and slope are sent automatically to Auriga, where you can see your actual progression in plan or elevation view."

CaversLass said:
He was getting fairly good results though using a tape and a rock,
I've recorded data on rocks before, having forgotten to bring a notebook.  Makes for a heavy tackle-bag by the end of the survey...
 

menacer

Active member
Phil gave me a handy tip for checking if your pony has been happily groomed fed and watered.
Find yourself a fixed to and from point, no where near any metal work and remove any wrist watches.

Take the same reading with pony faced up, 90 degrees left, upside down and 90 degrees right.
The readings should all be the same give or take a 2 degree error margin.
If they are wildly out its unlikely youll close any loops surveying...as discovered recently on a rods/bath survey trip on mendip.
Recalibrating it is relatively straight forward, the instructions are online on the shetlandattackpony.co.uk website.

As there are a few of us in mendip with Ponies im hoping to set up a permanent recallibration station (with 12 fixed stations of known compass clino) thing in the library at the Wessex...just need to ask the wonderful committee for permission ...  :kiss2:
 

graham

New member
Would a pony not be affected in some way by being surrounded by plumbing & electrical gubbins inside Upper Pitts?

And wouldn't the distances be a tad on the short side for good calibration shots?
 

menacer

Active member
graham said:
Would a pony not be affected in some way by being surrounded by plumbing & electrical gubbins inside Upper Pitts?

And wouldn't the distances be a tad on the short side for good calibration shots?
No  :)

http://www.shetlandattackpony.co.uk/downloads/manual2.pdf
read the bit on how to calibrate...as long as there are no electrical wires or pipes running across the middle of say the library it shouldnt be a problem....
 

pete h

New member
menacer said:
graham said:
Would a pony not be affected in some way by being surrounded by plumbing & electrical gubbins inside Upper Pitts?

And wouldn't the distances be a tad on the short side for good calibration shots?
No  :)

http://www.shetlandattackpony.co.uk/downloads/manual2.pdf
read the bit on how to calibrate...as long as there are no electrical wires or pipes running across the middle of say the library it shouldnt be a problem....

central heating pipes maybe above ceiling and most certain to be wires as the light works.  :idea:
 

SamT

Moderator
surely your better off doing it outside somewhere  :coffee:

, prividing your not near any water mains - overhead cables, underground cables etc etc  ::)
 

menacer

Active member
So nobody's actually read the calibration method from the maker of the device then.....guys you only need to read the 1st 4 points and all your questions/thoughts/ponderings will be answered...
 
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