Rotary laser levels

The problem: Inside a building 9m by 12m, I need to mark horizontal lines around the walls at heights of 3.2m, 3.8m and 4.4m above floor level (assume the existing ground floor is none too level, so I will pick a datum point).
I'm assuming a rotary level is the best tool for the job. I was taught (donkeys years ago) to use a theodolite and surveyors level - so I'm assuming using the modern kit is the same big boys geometry?
Looking in screwfix, there's the cheapy stuff (I'd buy one) or there's the professional stuff (I'd probably hire it).
Is the difference one of durability? Usability? Acuuracy? Are the cheapies in fact near-useless crap for any serious task?
Is the best solution to mark a level baseline on the wall near ground level and then measure up from there at points all around the walls? Or would I be better trying to set the instrument up on a high masonry ledge ? (there's one at slightly more than 3.2m from the ground). That involves more faffing to set it up, but less error over vertical distances (and less object in the laser path to work around) - is it likely to make a scrap of difference anyway?
I'm going to be basing alotof work around this bit of marking out - so I'm willing to go to some trouble to get the most accurate results I can get.
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I have not used a rotary laser but have had good success with the old tried and tested method using ....
http://tinyurl.com/gtylg
I can't imagine the cheapo laser levels are much use - perhaps others have had some success? I saw one recently with an accuracy of 1mm per Meter. Hmm... that's a centimeter out in 10M - I'm sure the Water Level is better than that...
Roy
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I paid 5 in MAKRO for one that looks identical to this from Screwfix
http://www.screwfix.com/app/sfd/cat/pro.jsp?idt711&ts 744
It's good (for a fiver!) but the divergence of the line (or lack of) is not great and the accuracy is probably what you'd expect for 50.
However, as an alternative to using a water level for transferring points from one end of a room to another it's fine.
I suspect that someone will tell us that for a fiver I got what I paid for, which is true but if you'd paid 50 you might be a bit dissapointed.
Richard
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Cheap chinese shite. Self leveling is a must, I bought the basic S/F rotary level. Near impossible to get level, at the height you want. Then if you even breath in the same room, it'll move.
--
steve

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I bought a cheap Chinese self levelling turnable laser. It's magic. Unscrew the transit bolt underneath and plonk it down. Where it falls down is the brightness of the laser - it's got a prism to split it into a line and it's really not bright enough for outdoor use except on very dull days. I kept having to wait till dusk to use it.
I checked it by marking each end of the line then working it all the way round and then using a water level on the marks and it was spot on.
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Skipweasel
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contains these

I got the Aldi 20 self-levelling chinese laser a few months ago, was a huge help with a tiling job and useful when figuring out where the lumps and bumps in a floor were. I can imagine it will often be a help in future jobs. The first one I got was faulty though.
Before I got a Lidl laser level, not self-levelling, it was useful but the amount of effort getting it set up was well beyond the advantage gained. I expected the self-levelling might turn out to be as disappointing but I have been pleasantly surprised.
H
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Guy King wrote:

I used to use a laser in the aerospace industry to match up the radar, inertial navigation platform, guns and head up display. The target was mat black. I suspect that you would get a better view of the laser spot by using a piece of black card/paper to find the spot. The theory behind this 'should be' no reflective sunlight etc. I have not tried it myself, But I can't see why it should not be visible.

I think that this depends very heavily on the mechanical stability of the laser mechanism. I bought a cheap, tripod mounted one many years ago. It took me several days to achieve repeatability with it. The mechanical back-lash was enormous when I first got it home.
The bubble level was out to where the laser pointed. To check, lay the level on a long, stable, flat surface and use thin tape, masking tape will suffice, until you get the bubble to read the same result after turning it 180 degrees.
(Self levelling lasers can be checked the same way, by setting it up and then marking the wall at various points and then turning the laser 180 degrees (including it's mounting) and check again. Any inaccuracy will show up right away.)
Back to level/laser pointers...
Note, make sure that only one end, not the same end. e.g. make the left hand end of the level, as viewed, is positioned on the same edge of the tape at all times when rotating it.
If you can't achieve this calibration, the bubble has not been set to the frame of the level. The solution is to find a small block of wood, that is just wide enough to tap down the bubble's end, to achieve bubble to level accuracy. When you get the level to read the same both ways, then...
Try switching on the laser the right way up, mark a target at least 12 foot away and turn the level upside down and repeat the above (without removing/adjusting the tape and placing the level in exactly the same place.) Note. You will have to calculate the difference of height of the laser, to correct the laser spot from right way up, to up-side down. This should be with the laser docs you got with it.
This will prove the laser to level accuracy.
I hope that all this makes perfect sense, but I have just recently (ending about 1 1/2 hours ago) spent ten and a bit hours travelling from Preston, Lancs. to Warwick services and back. Normally a 4 to 5 hour trip, to meet up with our daughter, to hand back the g daughters for going home.
HTH
Dave
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Having tried it, shaded white card worked best. What tickles me is the catalogues describe the red glasses supplied with some laser devices to increase the visibility of the beam as "safety glasses". Red laser, glasses that pass red light - hmmm.
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This was just plonked on the workmate in the middle of the room. 'Cos it's self levelling it doesn't really matter provided there's no stiction.
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snipped-for-privacy@gglz.com wrote:

//snip//
how many times do you intend to do this or a similar job?
If once only, you can make up your own water level very easily and cheaply and get very good accuracy.
use 40mm waste pipe - available in 3m & sometimes longer lengths - with pushfit joints & 90 deg bends to make a flat bottomed U tube. The wide diameter is essential to avoid surface tension and water-pipe wall frictional drag. Done this way, you can make & remake the U tube easily to make multiple checks at different positions as often as you wish, though you do need a system for catching water as it drains - like a T with an access (inspection) cover at the foot of the U tube. The whole setup will be quite heavy when full of water so you need an improvised support system (bricks?). When done you can reuse the pipe for normal plumbing.
The distances you are talking about (9m & 12m) are quite large and there has to be considerable doubt that a pivot system for a cheap laser could provide much accuracy.
A quick calculation illustrates your difficulties with a laser: a point 9m distant projected at an accuracy of 0.1deg (quite good for cheap laser device) is accurate to only plus or minus 16mm; at 12m this becomes + or - 21mm. IMHE with care you can do far better than this with a water level, but note a hose pipe is no use as surface tension & friction will be too great. If you can find/fund pipe with a larger dia than 40mm, all the better, though the quantity of water might be hard to handle.
If you could obtain them, it might be possible to construct a diy static referencing system using accurately ground prisms (these are expensive - prices start at 50 each and disappear into the stratosphere), but even then you'd need to obtain a laser accurate to perhaps 0.01 degree to get real accuracy of 1mm or so, plus devise a highly accurate and stable vertical reference system.
Two possibilities for floats - I used table tennis like childens' play-balls which I bought in a toy shop for 50p or so (proper table tennis balls are too large) or you could try fishing floats. It is highly desirable that the vertical parts of the U tube should be a similar as possible.
HTH
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| | snipped-for-privacy@gglz.com wrote: |> The problem: Inside a building 9m by 12m, I need to mark horizontal |> lines around the walls at heights of 3.2m, 3.8m and 4.4m above floor |> level (assume the existing ground floor is none too level, so I will |> pick a datum point). |> |> I'm assuming a rotary level is the best tool for the job. I was taught |> (donkeys years ago) to use a theodolite and surveyors level - so I'm |> assuming using the modern kit is the same big boys geometry? |//snip// | |how many times do you intend to do this or a similar job? | |If once only, you can make up your own water level very easily and |cheaply and get very good accuracy. | |use 40mm waste pipe -
Transparent plastic tube widely available is easier, much the same method.
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Dave Fawthrop <dave hyphenologist co uk> Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
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Dave Fawthrop wrote:

//snip//
How does the cost compare?
You also need large dia tube - I have found anything less than 40mm gives too much friction.
Waste pipe is readily reusable & reconfigurable, thus net cost of clear presumably would be higher ?
Clear tube does have the advantage however of letting you see if there are any air bubbles, which kill the method if they form.
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Realistically, as it's a relatively unobstructed rectangular space, I'm going to use a laser and not a water level.
If I had lot's of corridor turns to negotiate I might give it a try, but I'm really not going to have a 12m water filled tube to ensure my levels are accurate across the building.
Rotary lasers seem to be the way to go, and I'm hearing enough that I'm concerned that cheap rotary levels are not consistent between the levelling mechanism/spirit levels and the projected beam. There seems to be no cheap and cheerful self-levelling rotary lasers yet.
Hire prices on pro instruments (self-levelling 150/week) are sufficiently high to make buying a manually levelling pro instrument to look the most practical prospect (150-300).
How flexible are the beasts for other application? Presumably with rotation off I can use the static beam to align drains - can you shim up one end so they are off-level to set guttering as well? I can see me knocking up a jig to get the most out of it.
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I've got one - but it's only self-levelling, not self-rotating. Aldi or Lidl, one of the two.
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Guy King wrote:

how accurately?
A high quality spirit level at best gives +/- 0.5mm in 1m - which would project +/- 6mm over 12m.
If that degree of inaccuracy satisfies the OP he could consider acquiring a high quality level & clamping a laser pointer on top of it, but somehow I fancy errors in positioning would mount up. OP should check any laser for visibility at 12m before purchase.
OP would be well advised to look for ways of setting out by at least 2 independant to guard against errors.
OP also asked about setting gutter drops etc - best to set levels and measure up or down by ruler.
HTH
IMHO .
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As far as I can tell, very well. I checked it with a water tube along about a 15' run and couldn't spot any deviation at all. Repeatable, too. Moved it several times and it came out the same each time.
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After serious thinking jim wrote :

I have one of the Aldi/Lidl 20 self leveling ones which produces either a vertical line, horizontal line, or both - though manual rotation. I recently used it over 5m and comparing it against a water level found absolutely no discernable error. I might have been lucky with the factory calibration of mine though. The only problem is that it becomes quite a dim line at these distances, so you have do the marking out at dusk if out of doors.
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Regards,
Harry (M1BYT) (L)
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Exactly the same as my experience with the same unit.
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Skipweasel
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snipped-for-privacy@gglz.com wrote:

I bought one of the Lidl/Aldi levels with a laser in it plus tripod some time back thinking it would be useful sometime. It's not self levelling which would have been a bonus but another possible source of error. Anyhow I've been using it for a garage makeover involving a large area of concrete laid in 4 bays, all of which are remarkably level and joining up without any steps or errrors and also in setting up the timberwork and guttering. For 10 this was a bargain in terms of the ease of getting all my levels correct. It took a little time to set up but having tried to use water levels on various occasions .... uhhhh !!! bad memories.
Oh and yes I set it at a very slight angle to set the gutter brackets - a nice little red spot on each one as I moved along the wall.
I really can't see the point in spending some serious money unless it was going to be lost in some major expenditure.
Rob
Rob
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It will be. I'm will go to some lengths and some expense to get this right as as a lot of work depends on it. So have just spent 150 on ebay for DeWalt rotating, manual set up laser. Will give some feedback on how well it shapes up.
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