Willy Eckerslyke
6 years ago
Hello all, have any of you had any success using a cheap digital altimeter underground?
I'm not after great accuracy, just an comparison between floor levels across a relatively short distance. I.e. take a reading at floor level, clamber over a fall, round the corner and get an idea of the height difference.
It could be done in steps with a spirit level and tape measure but if there was a £20 device that gave adequate results in a single go, it would make life easier.
Accuracy of a foot or two over a height difference of 20-30 would be sufficient.
"The true crimefighter always carries everything he needs in his utility belt, Robin"
RJV
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6 years ago
My bike Garmin has one but I'd never treat it as more than a guide - even on a short ride there can be significant differences with people using similar devices. There's often a lag too.
Morlock
6 years ago
If the altimeter is a GPS unit virtually useless with an accuracy of 10-20 meters. That assumes you can get a GPS signal underground. Barometric unit would be fairly accurate though.
AndyJ23Uk
6 years ago
i has attempted this using a garmin GPS that has an independant barometer chip and results are " mixed " mostly - a lot of faff [ calibration of local pressure > actual altitude ] .

the use you want " ie what is the vertical separation between 2 points " is easiest and most accurate - at least over a short timespan

i suppose a dediated stand alone instrument would be easier in many regards

where i can get line of sight between 2 points - i prefer to use a DISTO - it calculates basic trig functions with one button press
Willy Eckerslyke
6 years ago
Thanks, yes I should have mentioned that I wasn't thinking of a GPS one. I hadn't realised that some Garmins have a barometric altimeter built in. We have an Etrex 30 so I'll try experimenting with it. That might well be all we need for this, which would be good news.

All we're actually trying to work out, is whether a dig is feasible. I.e. is the passage we're trying to find just a metre below the spoil or buried 3-4m down with no chance of ever being reached?

I do like the idea of getting a Disto and learning how to survey properly but that's a bit more than I want to commit to at the moment.

Thanks. :flowers:
"The true crimefighter always carries everything he needs in his utility belt, Robin"
RJV
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6 years ago
Could the fall affect the air pressure and skew the readings?
Willy Eckerslyke
6 years ago
"RJV" wrote:

Could the fall affect the air pressure and skew the readings?


We've just been chatting about that. There was no discernible air flow through the fairly small opening between the two areas so perhaps not. But it's all magic to me - I'm still struggling to get my head around the fact that it could work at all!
"The true crimefighter always carries everything he needs in his utility belt, Robin"
Pete Monkhouse
6 years ago
How about a bit of (say) 10mm bore flexible pipe, water filled, pressure gauge at each end? Take one end to the far side of the blockage and read both gauges? Assuming the pipe is full all the way through you can calculate the head of water at each end....
ttxela
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6 years ago
"Willy Eckerslyke" wrote:


It could be done in steps with a spirit level and tape measure but if there was a £20 device that gave adequate results in a single go, it would make life easier.



One of those fancy modern levels with a laser projecting a point on the wall might enable you to use this method with less steps?
Willy Eckerslyke
6 years ago
"Pete Monkhouse" wrote:

How about a bit of (say) 10mm bore flexible pipe, water filled, pressure gauge at each end? Take one end to the far side of the blockage and read both gauges? Assuming the pipe is full all the way through you can calculate the head of water at each end....


Sounds a great idea Pete, thanks. A little cumbersome perhaps for this particular site though as it involves quite a long crawl through extreme flakiness to get there.
"The true crimefighter always carries everything he needs in his utility belt, Robin"
Willy Eckerslyke
6 years ago
"ttxela" wrote:

One of those fancy modern levels with a laser projecting a point on the wall might enable you to use this method with less steps?


Yes, that may well be the best solution - and would be nicely portable, thanks Alex.
"The true crimefighter always carries everything he needs in his utility belt, Robin"
sinker
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6 years ago
"Willy Eckerslyke" wrote:

"ttxela" wrote:

One of those fancy modern levels with a laser projecting a point on the wall might enable you to use this method with less steps?


Yes, that may well be the best solution - and would be nicely portable, thanks Alex.



I have such a device. I'll bring it next time we go down there....not sure I'm all that happy about venturing into the place where I assume you're going to use it though :lol: :surrender:
Yma O Hyd....
TwllMawr
6 years ago
One of these?... a manometer. Lowest range is -1 to 3bar , accuracy 0.2% FS. So for the 4 bar range- 8mb? What's that in barometric height?

Their used for measuring low pressure sealed vessels during live process commissioning. Very sensitive, as I had to reference zero the thing as the weather drifted. They're used as fixed instruments so I've no experience of what happens if jostled along a dig between measurements. I may be able to borrow one.

www.keller-druck.com/home_e/paprod_e/leo2_e.asp

Pete Monkhouse
6 years ago
1 mbar is about 8 metres of height.
TwllMawr
6 years ago
"Pete Monkhouse" wrote:

1 mbar is about 8 metres of height.



Thanks.

Could be the error for those is 0.1% FS. Nevertheless that's still 32Metres... worst case of course across its range.
TwllMawr
6 years ago
"sinker" wrote:

"Willy Eckerslyke" wrote:

"ttxela" wrote:

One of those fancy modern levels with a laser projecting a point on the wall might enable you to use this method with less steps?


Yes, that may well be the best solution - and would be nicely portable, thanks Alex.



I have such a device. I'll bring it next time we go down there....not sure I'm all that happy about venturing into the place where I assume you're going to use it though :lol: :surrender:



If its the type I'm thinking of, then I wouldn't like to be you explaining where it got trashed:lol:
sinker
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6 years ago
"TwllMawr" wrote:

"sinker" wrote:

"Willy Eckerslyke" wrote:

"ttxela" wrote:

One of those fancy modern levels with a laser projecting a point on the wall might enable you to use this method with less steps?


Yes, that may well be the best solution - and would be nicely portable, thanks Alex.



I have such a device. I'll bring it next time we go down there....not sure I'm all that happy about venturing into the place where I assume you're going to use it though :lol: :surrender:



If its the type I'm thinking of, then I wouldn't like to be you explaining where it got trashed :lol:



No panic, I'll bring this one:
https://shop.bosch-professional.com/gb/en/product/line-laser-gll-3-50--34157--0601063800 

NOT this one:
https://leica-geosystems.com/en-gb/products/total-stations/robotic-total-stations/leica-viva-ts16 

:lol:
Yma O Hyd....
ttxela
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6 years ago
"sinker" wrote:

"TwllMawr" wrote:

"sinker" wrote:

"Willy Eckerslyke" wrote:

"ttxela" wrote:

One of those fancy modern levels with a laser projecting a point on the wall might enable you to use this method with less steps?


Yes, that may well be the best solution - and would be nicely portable, thanks Alex.



I have such a device. I'll bring it next time we go down there....not sure I'm all that happy about venturing into the place where I assume you're going to use it though :lol: :surrender:



If its the type I'm thinking of, then I wouldn't like to be you explaining where it got trashed :lol:



No panic, I'll bring this one:
https://shop.bosch-professional.com/gb/en/product/line-laser-gll-3-50--34157--0601063800 

NOT this one:
https://leica-geosystems.com/en-gb/products/total-stations/robotic-total-stations/leica-viva-ts16 

:lol:



I was thinking more of this sort of thing:

https://www.clasohlson.com/uk/Bosch-PLL1P-Laser-Spirit-Level/40-8663?gclid=EAIaIQobChMIn7K885jp4gIVl_hkCh0yDQjHEAQYASABEgI25vD_BwE 

:lol:
Willy Eckerslyke
6 years ago
:thumbsup:
"The true crimefighter always carries everything he needs in his utility belt, Robin"
sinker
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6 years ago
"ttxela" wrote:

"sinker" wrote:

"TwllMawr" wrote:

"sinker" wrote:

"Willy Eckerslyke" wrote:

"ttxela" wrote:

One of those fancy modern levels with a laser projecting a point on the wall might enable you to use this method with less steps?


Yes, that may well be the best solution - and would be nicely portable, thanks Alex.



I have such a device. I'll bring it next time we go down there....not sure I'm all that happy about venturing into the place where I assume you're going to use it though :lol: :surrender:



If its the type I'm thinking of, then I wouldn't like to be you explaining where it got trashed :lol:



No panic, I'll bring this one:
https://shop.bosch-professional.com/gb/en/product/line-laser-gll-3-50--34157--0601063800 

NOT this one:
https://leica-geosystems.com/en-gb/products/total-stations/robotic-total-stations/leica-viva-ts16 

:lol:



I was thinking more of this sort of thing:

https://www.clasohlson.com/uk/Bosch-PLL1P-Laser-Spirit-Level/40-8663?gclid=EAIaIQobChMIn7K885jp4gIVl_hkCh0yDQjHEAQYASABEgI25vD_BwE 

:lol:



Works just as well :thumbup:
I'm assuming we don't require 0,3mm accuracy?? ;)
Yma O Hyd....
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