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.

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

I paid £5 in MAKRO for one that looks identical to this from Screwfix

http://www.screwfix.com/app/sfd/cat/...74711&ts=16744

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

In message om,
" writes
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?

Cheap chinese ****e. 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

The message
from Steven Briggs contains these
words:

Cheap chinese ****e. 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.

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.

--
Skipweasel
Pay no attention to that man behind the curtain.

"Guy King" wrote in message
...
The message
from Steven Briggs contains these
words:

Cheap chinese ****e. 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.

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.

--

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

Guy King wrote:
The message
from Steven Briggs contains these
words:


Cheap chinese ****e. 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.


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 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 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.

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

The message
from Dave contains these words:

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 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.

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.

--
Skipweasel
Pay no attention to that man behind the curtain.

The message
from Dave contains these words:

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.

I think that this depends very heavily on the mechanical stability of
the laser mechanism.

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.

--
Skipweasel
Pay no attention to that man behind the curtain.

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 - 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

On 19 Aug 2006 15:34:14 -0700, "jim" wrote:

|
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.
--
Dave Fawthrop dave hyphenologist co uk Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
newsreader, say Agent, and a newsserver, say news.individual.net. These
will allow them: to see only *new* posts, a killfile, and other goodies.

Dave Fawthrop wrote:
On 19 Aug 2006 15:34:14 -0700, "jim" wrote:

//snip//

|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.

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.

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.

The message . com
from " contains these words:

There seems to be no cheap and cheerful self-levelling rotary lasers yet.

I've got one - but it's only self-levelling, not self-rotating. Aldi or
Lidl, one of the two.

--
Skipweasel
Pay no attention to that man behind the curtain.

wrote:
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.

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

It happens that jim formulated :
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.

With all due respect Jim, what friction, drag and surface tension are
we talking about that would need such a wide diameter pipe?

I have used a home made water level of 5mm internal diameter over
distances in excess of 50m, without even the advantage of the larger
diameter pipe at the ends. The only problems I found were due to
trapped bubbles in the pipe. Rigid 40mm pipe would be equally likely to
suffer trapped air and even more difficult to get out if the horizontal
is not level.

My water level produced reference marks were cross checked against the
best professional surveying equipement, by professional surveyors and
found to be spot on. It is just a matter of ensuring there are no
bubbles trapped and waiting a few seconds for the level to properly
settle. The only source of error is then the user being aware of the
surface tension producing a choice of two levels.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk