Author Topic: Surveying equipment  (Read 11596 times)

Offline Ouan

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Re: Surveying equipment
« Reply #50 on: April 01, 2008, 03:04:42 am »
Hi

Had a test drive of a SAP, used with with a Disto, last week in a 325m long cave in Thailand.

Came to the same conclusions as most of the folks above: my geriatric companion had problems holding the SAP and Disto steady enough for readings over 20m (longest leg achieved 26m); sighted onto survey book; for two old, blind buggers with glasses the SAP is better than Suuntos in hot and steamy conditions; SAP gives you get two readings at once and you know where you are pointing it, plus electronic back up of data; SAP and Disto are lighter and more compact that Suuntos and tape.

Our accuracy wasn't brilliant: one 100m loop had a 6% closure error and a 92m loop had a 3% closure error.  According to Walls the errors are mainly in the distances, so next time we'll take the distances twice to make sure the Disto is actually measuring to the target and not bouncing off the wall behind.  However, the survey was good enough for our purposes.

Ouan

Offline Charlie

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Re: Surveying equipment
« Reply #51 on: April 01, 2008, 09:53:59 am »
Have you considered using a "lolly" as in this Avalon item
http://www.scavalon.be/avalonuk/technical/laserclino.htm  ?



It is easier to just stick a reflector to the back of your survey pad...

Charlie
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Offline Charlie

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Re: Surveying equipment
« Reply #52 on: April 01, 2008, 10:04:50 am »
A few years ago I met an action photographer who used one of these devices http://www.electromax.com/fotosnipercamera.html



I means you are seadying the camera against your shoulder and with both hands so you can get a steady shot while balancing on boulders etc when you cant use a tripod.

Could a similar system [folding shoulder stock, pistol grip or similar] be set up to steady your SAP or disto? It seems to offer the stability of a tripod without the faff of setting one up at each survey station.

just a thought...
Charlie
If you gaze long into the abyss then the abyss gazes also into you

Offline potholer

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Re: Surveying equipment
« Reply #53 on: April 01, 2008, 01:06:04 pm »
For limiting shake, would a monopod be good enough?
A cheap walking pole should be pretty durable, and could at least be dismantled to remove mud, etc if used in messier caves.

Offline seddon

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Re: Surveying equipment
« Reply #54 on: April 01, 2008, 01:37:51 pm »
Doesn't look nearly so warry though, Potholer!
Starless River Caving Equipment @ www.starlessriver.com

Offline dl

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Re: Surveying equipment
« Reply #55 on: April 01, 2008, 06:54:17 pm »
A garden cane and a snoopy loop work well to reduce vibration with a disto.  Not as sexy as a rifle grip setup though  :)


truescrumpy

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Re: Surveying equipment
« Reply #56 on: April 01, 2008, 06:59:04 pm »
Having just spent a week surveying with a laser measure for the first time, I can provide some first hand feedback.

Firstly, it is far, far quicker than surveying with a tape. Especially for Left,Right,Up,Down readings and when only 2 people are doing the surveying. Allows the sketcher to keep their hands clean for drawing too.

Secondly, it is difficult to hold the spot steady on long (20m+ legs). But if you choose your target carefully so there is not anything next to it where the distance will be very different (e.g. choose a flat wall or stand in front of it and use your body as a target) then this can be overcome. Double check long readings to be sure. We rarely get legs over 10m anyway in my personal experience.

Thirdly, the laser is a great help in choosing stations, as it instantly indicates which points along the passage are visible from the last station when the user shines it around from the last station.

Finally one drawback we had not anticipated. One of our team was red/green colour blind, and could not actually see the spot of the red laser on mud and rock!

Overall I was completely sold on them. We worked as a pair, me drawing and recording the figures, and my survey partner reading the instruments. I set stations and used my hand as a target, so no problems with reflections off difficult surfaces. Surveying in wet cold conditions was fast and efficient. We could also measure the heights of avens. Got a reading of 35m up one, so reflections off rock are possible over long distances.



Thanks for the update  :thumbsup:

Offline menacer

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Re: Surveying equipment
« Reply #57 on: April 04, 2008, 05:56:16 pm »
Our accuracy wasn't brilliant: one 100m loop had a 6% closure error and a 92m loop had a 3% closure error.

There are a lot of reasons why your error may have been such, but one particular thing to note, when using a disto with a regular compass clino or a pony, is that the battery from the disto will  cause a magnetic shift when placed next to the compass/pony.
Wave a battery over your compass/pony and  coo in awe at the swaying needle/digital reading.... :down:
Its not a major problem , just keep the disto and the compass away from each other when taking the compass reading, about 6 inches was enough (without getting it out and double checking)


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Offline Cap'n Chris

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Re: Surveying equipment
« Reply #58 on: April 04, 2008, 06:13:38 pm »
A few years ago I met an action photographer who used one of these devices http://www.electromax.com/fotosnipercamera.html


Lol!

Someone had one of these, in a bag, a few years back (IIRC) and stopped off for a drink or two in one of the pubs in Cheddar Gorge, of an evening.

Within half an hour the place was surrounded by armed police.

darkplaces

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Re: Surveying equipment
« Reply #59 on: April 04, 2008, 11:10:17 pm »
The police and people are jumpy at anything these days!

Myself and another are using a laser range finder, as used in construction and a compass to survey A <secret> Quarry, results will be copyright free and published in good time. I might even write a book!

Offline Ouan

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Re: Surveying equipment
« Reply #60 on: April 05, 2008, 03:31:51 am »
There are a lot of reasons why your error may have been such, but one particular thing to note, when using a disto with a regular compass clino or a pony, is that the battery from the disto will  cause a magnetic shift when placed next to the compass/pony.
Wave a battery over your compass/pony and  coo in awe at the swaying needle/digital reading.... :down:
Its not a major problem , just keep the disto and the compass away from each other when taking the compass reading, about 6 inches was enough (without getting it out and double checking)

The affect the disto has on a compass had been noted before when we had tried to duct tape a regular compass to the back of it to make a survey unit. The compass stops going round, which is OK for surveying a dead straight mine tunnel, but not too good in a cave.

I'm blaming the closure error on a combination of early onset Parkinson's and DTs.   

Offline footleg

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Re: Surveying equipment
« Reply #61 on: April 05, 2008, 12:11:17 pm »
The police and people are jumpy at anything these days!

I know. A friend of mine was coming up to the Dales for a caving fireworks weekend a few (>10) years back, and had made a 4ft long bright yellow missle style rocket. He got as far as Sheffield on the train when the police approached him on the station platform. Apparently a member of the public had raised a concern. He was allowed to continue his journey provided he left the rocket in their care. I expect they had a good police fireworks night that year!

I do wonder what might have happened these days if a similar incident occurred  :o