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Default Reference Instruments - DIY Laser Level.

I contributed the U - Tube to the DIY Laser Level thread as this is the
only rudimentary reference that I can think of for getting something
level.

In the vertical axis we have the "Plumb Line". This is what I call a
reference for getting something to stand or hang vertically.

I have asked other people what they consider is a horizontal refrence
instrument and they all say the "Spirit Level". This I disagree with
as it can be adjusted or altered. This is why I say the "U - Tube is
the reference for horizontals as there is no adjustment, you just wait
for the liquid to settle.

What did the Egyptians, Romans et al use for horizontals. They could
have constructed a form of U-Tube but not a moveable/flexible one.

OK Pundits, what do you rekon?

Chris

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Malcolm Stewart
 
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Default Reference Instruments - DIY Laser Level.

wrote in message
oups.com...
I contributed the U - Tube to the DIY Laser Level thread as this is the
only rudimentary reference that I can think of for getting something
level.

In the vertical axis we have the "Plumb Line". This is what I call a
reference for getting something to stand or hang vertically.

I have asked other people what they consider is a horizontal refrence
instrument and they all say the "Spirit Level". This I disagree with
as it can be adjusted or altered. This is why I say the "U - Tube is
the reference for horizontals as there is no adjustment, you just wait
for the liquid to settle.


Chris


You really should have asked this in a surveying group.
The beauty of a spirit level, at least a decent one as fitted to a
theodolite, is that it's possible to make the base of the theodolite (very
close to true) level by turning it through 180degrees, and taking out about
1/2 the error. Repeat after turning through 180 degrees. Repeat at
90degrees etc. In a way, surveying as practised up to about 15-20 years
ago was all about "managing" the inevitable errors in the instruments as a
result of manufacturing and centring erros. So most readings would be
repeated 180 degrees from the first, and another complete set taken with the
telescope turned over. Careful work reduced erros to around 1" of arc, or
better for map making. Modern instruments use electronics, and some of the
"problems" are hidden.

One of my theodolites, a Wild T2, has simple, but sensitive vials, for all
axes. The other, a Kern DKM2-A, uses reflection from the surface of liquid
for one of its references, so you're effectively back to the plumbline. With
care, both can measure to 1" repeatedly, and placed side by side, agree to a
remarkable degree as to where the horizon is.
(Whilst lurking on the previous thread, I compared my surveyor's level
against my cheap laser level. No contest.)
--
M Stewart
Milton Keynes, UK
http://www.megalith.freeserve.co.uk/oddimage.htm




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Peter Taylor
 
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Default Reference Instruments - DIY Laser Level.


wrote in message
oups.com...
I contributed the U - Tube to the DIY Laser Level thread as this is the
only rudimentary reference that I can think of for getting something
level.

In the vertical axis we have the "Plumb Line". This is what I call a
reference for getting something to stand or hang vertically.

I have asked other people what they consider is a horizontal refrence
instrument and they all say the "Spirit Level". This I disagree with
as it can be adjusted or altered. This is why I say the "U - Tube is
the reference for horizontals as there is no adjustment, you just wait
for the liquid to settle.


Putting on my anorak for a second, given that we live on the surface of a
sphere, there is no definite answer to this. Over 1km distance, the water
level of a lake will have curved 10mm lower than a straight sighting looking
out into space. In a similar way, because a plumb bob always points to the
centre of the earth, two readings any distance apart will not be truly
parallel.

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Andy Dingley
 
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Default Reference Instruments - DIY Laser Level.

On Wed, 11 Jan 2006 00:29:37 -0000, "Peter Taylor"
wrote:

Putting on my anorak for a second, given that we live on the surface of a
sphere, there is no definite answer to this.


Gravitational isopotential surface, as a rough approximation (ignoring
local geological variations).



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Posted to uk.d-i-y
 
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Default Reference Instruments - DIY Laser Level.

What did the Egyptians, Romans et al use for horizontals. They could
have constructed a form of U-Tube but not a moveable/flexible one.

OK Pundits, what do you rekon?

Chris


Those of you with 1km. window sills should watch out!!

Seriously though thanks for the answers. I usually do do that with a
spirit level, turn it through 180 deg and see if the difference is the
same.

The towers of the Forth Road Bridge are different distances apart from
base to tip, can't remember what it is but it can be calculated. Also
driving across the Nullabor plain can be enlightning.

Chris.

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Rob Morley
 
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Default Reference Instruments - DIY Laser Level.

In article .com
wrote:
I contributed the U - Tube to the DIY Laser Level thread as this is the
only rudimentary reference that I can think of for getting something
level.

In the vertical axis we have the "Plumb Line". This is what I call a
reference for getting something to stand or hang vertically.

I have asked other people what they consider is a horizontal refrence
instrument and they all say the "Spirit Level". This I disagree with
as it can be adjusted or altered.


You just turn it the other way and check if it's still level.
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Peter Taylor
 
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Default Reference Instruments - DIY Laser Level.


"Andy Dingley" wrote in message
...
On Wed, 11 Jan 2006 00:29:37 -0000, "Peter Taylor"
wrote:

Putting on my anorak for a second, given that we live on the surface of a
sphere, there is no definite answer to this.


Gravitational isopotential surface, as a rough approximation (ignoring
local geological variations).


Yes, you have a valid point there. But the local geological variations do
play an important part. Don't forget here in GB we're on the other side of
the earth from the bulk of its ferrous mass. Maybe in the middle of the
Gobi desert your point would be more relevant. Not forgetting also that the
isopotentiality is largely cancelled out by the refraction of gravitational
pull caused by the Doppler effect of the Moon in its third phase, I feel
maybe your concern takes on rather insignificant proportions. However, put
up a theory and there'll usually be someone who wants drive a hole through
it, so, as always, I stand to be corrected.

I am now closing this topic and returning to my main occupation of caring
for my antique raingauge collection.

Peter


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Chris Bacon
 
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Default Reference Instruments - DIY Laser Level.

Peter Taylor wrote:
Don't forget here in GB we're on the other
side of the earth from the bulk of its ferrous mass.


What?? The earth is by composition about 1/3 iron. Do
you say that minor (in the great scheme of things)
concentrations of this element in extractable form
have a serious influence on the composition of one
hemisphere? If no, what do you say?


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Dave
 
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Default Reference Instruments - DIY Laser Level.

Peter Taylor wrote:

Not
forgetting also that the isopotentiality is largely cancelled out by the
refraction of gravitational pull caused by the Doppler effect of the
Moon in its third phase


Can you please expand on this doppler effect? I would think that it
occurred on all aspects of gravitational pull, regardless of the moon's
phases.

Dave
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Peter Taylor
 
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Default Reference Instruments - DIY Laser Level.


"Dave" wrote in message
...
Peter Taylor wrote:

Not forgetting also that the isopotentiality is largely cancelled out by
the refraction of gravitational pull caused by the Doppler effect of the
Moon in its third phase


Can you please expand on this doppler effect? I would think that it
occurred on all aspects of gravitational pull, regardless of the moon's
phases.

Dave


Yes by all means. For certain people, and under specific conditions during
the third phase of the moon, the Doppler effect causes them to turn their
backs and wait while someone uses a key to increase the torsion of their
life-force.

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Dave
 
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Default Reference Instruments - DIY Laser Level.

Peter Taylor wrote:

"Dave" wrote in message
...

Peter Taylor wrote:

Not forgetting also that the isopotentiality is largely cancelled out
by the refraction of gravitational pull caused by the Doppler effect
of the Moon in its third phase



Can you please expand on this doppler effect? I would think that it
occurred on all aspects of gravitational pull, regardless of the
moon's phases.

Dave



Yes by all means. For certain people, and under specific conditions
during the third phase of the moon, the Doppler effect causes them to
turn their backs and wait while someone uses a key to increase the
torsion of their life-force.


Very nicly put :-)

Thanks Dave
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