Auto levelling laser levels

[akis]

Auto levelling laser level - can the horizontal line be pointed upwards or downwards?

I think the levelling mechanism is a float of some kind, if you tap it you can see the line wobbling until it settles.

But when you try to point it up or down it completely messes up and does not keep verticals or horizontals, it actually draws slanted lines.

I think this may be an intrinsic limitation of its auto-levelling mechanism, or maybe there are better models that can do it? Does anyone know?

PS: I take it back, not a float but a mechanical weight and a hall effect switch maybe?

[Gyro]

It's just a pendulum. Bearings at the top let it hang vertically - side to side and front to back.  Some of the better ones have magnetic eddy current damping to speed up settling and a contact that cuts off the laser when it's tilted out of its free swinging range.

You're never going to be able to make the horizontal line higher or lower than the level itself... The beam is horizontal. 

[eKretz]

No you can't point the level up or down. It is designed to be used nearly level. With some levels there is some slight amount of tolerance designed into the swing mechanism but if you point the level up it will just end up causing excess friction on the swing mechanism and hurt accuracy. If you need the laser line higher, raise the level - this is why they're often used on tripods. The other thing you can do is simply create your own line by measuring from the laser line and making marks on the surface then drawing a line between or setting up a string.

[tautech]

Many have an auto shutdown or beep if run not nearly level.

Get a vertical one or better still one of the tiny 3 axis ones. Some are tiny little cubes and you can place them most anywhere on a nearly level surface for a vertical line and 2 horizontals, 90^o to each other.

[akis]

I just looked at it closely, it seems there is a monolithic block incorporating all three lasers and mirrors. The whole block seems to be hanging from the top, with all the lasers below. Just like a pendulum that swings to all directions.

The horizontal and vertical beams are fixed to be perfectly horizontal and vertical, but easily the horizontal beam could have a vertical offset, so even though the pendulum is perfectly level the beam is directed upwards say by 45 degrees. And you could even have a step adjuster for the vertical offset. I presume this is achievable even if not commercially available?

[tautech]

Sounds like you're looking for a line laser not a laser level.
Construction laser levels are quite accurate over some distance while line lasers are intended for use within a room.

Some explanation of just what you're trying to do will help with recommendations......even a good plumb bob can save the day. 

[akis]

Some explanation of just what you're trying to do will help with recommendations......even a good plumb bob can save the day. 

"Have an instrument that I can point to anything around me and it will draw a horizontal line exactly at the height that I want, without having to change the instrument's height."

[Gyro]

That means that you would have to take it apart and adjust the laser optics on the pendulum (without disturbing its horizontal accuracy) every time you want a line at a different height. Doesn't sound very practical.

Also... and probably rather more problematic - if you didn't have the laser level at exactly 90 degrees to the wall, you'd get a slanting line. 

EDIT: In fact, even at 90' and assuming you'd adjusted it upwards you'd get a nice smily face line. 

[Zenith]

"Have an instrument that I can point to anything around me and it will draw a horizontal line exactly at the height that I want, without having to change the instrument's height."

From my limited experience with these things, they have a pendulum, (so no messing with spirit levels) you set them on a surface , close to level and at the right height, which you contrive somehow, and you have a level line around the room, which could be a very large room. I'm sure the one I used only did a horizontal line. Very useful for DIY, even advanced DIY, but probably not good enough for site surveyors. Now I believe you can pay a lot for laser levels.

Water levels were the old school way of doing things, low tech, awkward to use, but accurate, unless you are worried about the curvature of the earth.

Frankly, what you describe sounds like magic to me.

[tautech]

Some explanation of just what you're trying to do will help with recommendations......even a good plumb bob can save the day. 

"Have an instrument that I can point to anything around me and it will draw a horizontal line exactly at the height that I want, without having to change the instrument's height."

Then any laser level can do that BUT only at the height you set it up at.

To get level lines at different heights you have but 2 options:
Offset a line from the laser line. Mark the line ends and flick a chalk line between them.
Use a camera tripod with a rack and pinion vertical adjustment to get the laser line to the height you want

[Gyro]

... or get someone to hold it at the right height against an adjacent vertical surface.

[akis]

Then any laser level can do that BUT only at the height you set it up at.

Then I think I had a great business idea. Set your laser level on a tripod / surface / rock, point it to the right direction, adjust horizontal beam up-down until at the precise height you need.

[tautech]

Then any laser level can do that BUT only at the height you set it up at.

Then I think I had a great business idea. Set your laser level on a tripod / surface / rock, point it to the right direction, adjust horizontal beam up-down until at the precise height you need.

You need to play with levels some more. 

Any surface that is NOT perfectly parallel to the level will show a sloping laser line.
Gyro points this out.

There's squillions of different laser levels already available, have a look on Aliexpress using a few different search keywords.

[Zenith]

Then I think I had a great business idea. Set your laser level on a tripod / surface / rock, point it to the right direction, adjust horizontal beam up-down until at the precise height you need.

You've got something there. You could even as a phase 2 development, have a laser pointing upwards into a rotating prism and so get a 360 degree line, which I'm sure hasn't been done before.

Let us know when the company you found is about to go public. I think we deserve to be let in early on the act, and given time to liquidate other investments in readiness

[eKretz]

No, this isn't an idea that will work well... One word reason for that - parallax error. When the laser is set level to put the line out, it's as dead level as it can get. So any surface not inline with the initial surface the beam is hitting also has a line that is inline with that initial one. If you start deflecting the beam that won't be the case anymore and would take away a lot of the functionality and usefulness of the laser level. I like them just the way they are.

[Gyro]

You've got something there. You could even as a phase 2 development, have a laser pointing upwards into a rotating prism and so get a 360 degree line, which I'm sure hasn't been done before.

Rotary laser levels are very common, they're used by builders, suspended ceiling fitters etc. You're 20 years or more too late. Try Screwfix.

Not cheap though, and of course they need to be perfectly leveled. [Edit: Actually they're mostly self-leveling these days].

[Zenith]

You've got something there. You could even as a phase 2 development, have a laser pointing upwards into a rotating prism and so get a 360 degree line, which I'm sure hasn't been done before.

Rotary laser levels are very common, they're used by builders, suspended ceiling fitters etc. You're 20 years or more too late. Try Screwfix.

Not cheap though, and of course they need to be perfectly leveled.

What? Are you telling me the one I found thrown away 16 years ago and took to bits didn't come out of an alien spacecraft like I was told?

I simply don't believe it - to quote Victor Meldrew.

[Gyro]

Sorry, I missed the subtle humor    I don't believe it!

[Zenith]

Sorry, I missed the subtle humor    I don't believe it!

TBH my way of looking at things is way too dry and it's got me into trouble before now. Peace.

[Brumby]

Some explanation of just what you're trying to do will help with recommendations......even a good plumb bob can save the day. 

"Have an instrument that I can point to anything around me and it will draw a horizontal line exactly at the height that I want, without having to change the instrument's height."

As mentioned above, simple geometry will prevent this from being possible using a simple laser beam in all but one very specific case.

If we are able to ignore the curvature of the Earth, then the beam from an ordinary laser level will point to every location that is the same height.  Distance from the laser level will be irrelevant.

However, once you incline the beam, then the height indicated will be proportional to the distance from the beam source according to the angle between the beam and horizontal.  In the case of the laser producing a planar trace, this angle will change according to the inclination of this plane, but also the instantaneous direction of the beam as it sweeps around.

If we do this and face the high point of the beam, then directly to our left and right, there will be one point on each side that is exactly level with the laser level and directly behind us will be a point that is as much below level as points in front are above - for the same distance from the laser.  Also note that these changes in angle are continuous (and smooth) as the laser beam traces out the plane.  In short, you will NEVER be able to get a level line with an inclined beam...

except...

If (and all these are critical):
 1. The laser beam produces a perfect cone^** (rather than a plane)  The angle subtended by this cone will be a major factor in determining the height of the beam when it hits the structure's surface.  The ability to change this angle would aid in setting different heights.
 2. The target structure is perfectly cylindrical.
 3. The laser unit is placed in the exact centre (the cylindrical axis) of the structure.
** It is taken as a given that the axis of rotation of the cone is vertical - just as the axis of the plane of rotation for a normal laser level is vertical.

This highlights a few reasons why the "simple" laser level works...
 1. There are no angles to play around with (they only make things difficult)
 2. The shape of the structure doesn't matter - other than shadows
 3. The location of the level is not critical and it's placement is more a matter of convenience



If you really wanted to do something like this, then there are a couple of ways I could imagine it happening.  The most practical way (I think) would be to measure the time-of-flight of a laser pulse to a given point and to use the angle of inclination/declination to determine the elevation of that target point.  As the laser beam scanned around the structure, it would do so in several passes at slightly differing angles, calculating the height of all points scanned and only "lighting them up" when the calculated elevation matched the target elevation (set by some means).

Sounds like an FPGA project.

[akis]

I do not know why almost all of you, except one, present me with problems rather than with solutions, even if partial. Like, "you can do something similar albeit with a few limitations".

Two points define a line.

If we are facing a properly built wall, drawing two points at dH vertical above the horizontal is easy. You need my laser level which draws two vertical lines and a horizontal line, and my laser distance meter. The hypotenuse of the two triangles is sqrt ( d^ 2+ dH ^ 2 ). dH is constant so I first measure d (horizontal distance to the wall along some vertical) and then I travel upwards along the same vertical until my distance meter reads the required hypotenuse. This could be done automatically of course with the lasers all in the same box and maybe an Arduino to run them.

The limitation is when instead of a perfectly vertical wall we are facing an uneven object, like a leaning wall or a rock face. Because then our horizontal distance is unrelated to the hypotenuse.

However inside a room or outdoors against a vertical wall it would work fantastic, and it does not need to drop off an alien spaceship...

[bugi]

I do not know why almost all of you, except one, present me with problems rather than with solutions, even if partial. Like, "you can do something similar albeit with a few limitations".

Because the path to a solution is difficult (and thus not necessarily known), so trying to be of at least some help, they tell at least which paths will not lead to a solution (i.e. the "problems").

Two points define a line.

If we are facing a properly built wall, drawing two points at dH vertical above the horizontal is easy. You need my laser level which draws two vertical lines and a horizontal line, and my laser distance meter. The hypotenuse of the two triangles is sqrt ( d^ 2+ dH ^ 2 ). dH is constant so I first measure d (horizontal distance to the wall along some vertical) and then I travel upwards along the same vertical until my distance meter reads the required hypotenuse. This could be done automatically of course with the lasers all in the same box and maybe an Arduino to run them.

If I understood correctly what you are trying to explain with that, then the simpler interpretation of measuring the distances only at the end points and then linearly sweep between them will not work correctly. (I based that interpretation from the initial "two points define a line.")  The more expanded interpretation of measuring things everywhere along the span of the line basically ends back with a variation of the previous time-of-flight -style solution. Even for a perfectly flat and vertical target surface.

Note that while two flat planes (wall and a specific type of laser-sweep) intersecting produces a straight line, beam-sweeping a plane from a device is done basically in polar coordinates, needing two varying angles of which the other angle varies non-linearly, instead of just one varying angle and a constant angle; the latter case can only draw cones or the extreme versions of a cone: flat surface at "0 degrees" or single line at "90 degrees". (I think the cone thing was already mentioned before.)



In general, I have toyed some ideas on laser line drawing over the years, too, starting soon after I heard first time about how accurate laser distance measurement can be (interference based back then). My idea has been a "bit" more elaborate idea of automatic 3D measuring of whole structures, then beaming laser figures all over the place as desired, be it horizontal lines, vertical lines, mm scale contours on surfaces (to make that floor _flat_), locations of to-be-built inner walls, drawing measurement values on surfaces, etc...  But hobby level accuracy on the measurements didn't quite reach the goal, at least not back then, but maybe the tech has come into the reach of hobbyist by now.

[akis]

"If I understood correctly what you are trying to explain with that, then the simpler interpretation of measuring the distances only at the end points and then linearly sweep between them will not work correctly. (I based that interpretation from the initial "two points define a line.")"

No I meant precisely two points. I am looking at a wall ahead and want to check if two nails, two windows or two shelves are at the same heights, without climbing up to measure.

You would aim the basic device and would "mark" the first point, say the first nail, and the device would distance measure the hypotenuse (where you are pointing at) and the horizontal distance on the vertical plane, and from that would work out the required height. You would then rotate the device to the left, and you would point it up and down the vertical until it beeped or flashed. It would beep when the new hypotenuse and the new horizontal distance matched the required height.

That would be the most simple device.

A more sophisticated device would scan upwards or downwards by itself. So you your rotate it gently and it would point the laser beam just at the right point.

An even more sophisticated device would even have rotating laser inside so it might even draw the whole line.

I cannot understand why even the basic device would not be an instant commercial success.

Imagine you are tiling your bathroom and need horizontal lines up to the ceiling. There is no tripod tat can reach the ceiling, so this device you'd set the tripod at 1.5m and it would be able to mark heights all the way to the ceiling without you needing to use your tape measure.

[Gyro]

Then any laser level can do that BUT only at the height you set it up at.

Then I think I had a great business idea. Set your laser level on a tripod / surface / rock, point it to the right direction, adjust horizontal beam up-down until at the precise height you need.

If you're actually serious about it it being a great business idea then you need to consider:

- Who would use it? It's difficult to think of applications where simply putting the level at the right height doesn't work.
- What market you're trying to address - homeowner or professional?
- How much cost would the market bear - could you make it for the selling price minus retailer / distributor markup etc.

The homeowner market it well provided for with line levels in the sub £50 range, I bought a very nice one from Lidl (<0.5mm/m) for less than half that with a 3yr warranty. The higher end ones run at about £100 (that's for a Leica) to £500

Professional 360' scanning lasers run at about £600-700). Those are probably always going to have to be horizontal due to the difficulty in distance sensing every point fast enough to accurately tilt a prism fast enough for the resulting scan line to look continuous (rather than a spinning dot). That sounds more like military technology and cost.

This brings us back to the simple line market then, do you think, with the addition of laser rangefinding, together with the ever-present need for self leveling (so that your horizontal distance measurement truly is horizontal). You also need some means of locking the pivot point in space so that the resulting points actually come out at the same height. You also need to be able to vertically steer the laser (continuously if producing a line) to a high degree of precision (needing angular feedback to produce the point / line).

If you feel that you can do that within the current market price range then you should certainly design your prototype and start touting it round the manufacturer / retail chain.

Gut feel says that you will miss the homeowner price range by a large margin, they will simply put their line laser at the required height. You need to come up with a convincing 'must have' argument for the professional end of the market. I really hope that you get lucky with that.

I hope you take this as positive input.

[Brumby]

At first, you specified that the device was to produce a line - then you continue with "Two points define a line".  That is actually a change in the specifications you gave for the original problem.  In this, you have given yourself a freedom in working the problem that you denied others.

But, moving right along....

I cannot understand why even the basic device would not be an instant commercial success.

Answer this question: What is your market?

Imagine you are tiling your bathroom and need horizontal lines up to the ceiling. There is no tripod tat can reach the ceiling, so this device you'd set the tripod at 1.5m and it would be able to mark heights all the way to the ceiling without you needing to use your tape measure.

You've never paid attention to a tiler at work, have you?