Posts made by bjornkn

@roger said:

Slightly related to this topic (barely). I was using "Google" search to locate a store with a cheap angle finder.

I suppose this implies that the iOS theodolite app didn't work very well then?

@Roger I never said that it couldn't be calculated if you know/measure one angle, the one between the lower and upper measurement.
It is when you don't have any known angle (including the 90 deg vertical wall) the problem arises, because when we don't have a vertical wall (and no angle) we can't know the height because the more the wall slants the lower it will actually be, and still have the same distance - and the smaller the angle gets.

@gaieus said:

Yeah, that's how a Greek (forget which one) measured the height of the pyramids som 2-2.5 millennia ago. And the pyramids do not have vertical walls either - the point is to take the measurement when the sun is low enough for the pyramid to cast shadow (it will be the point which casts the longest shadow anyway)

@unknownuser said:

I don't quite get how he did that using TIGs "similar triangles" method? TIG uses a vertical corner and 2 similar right-angled triangles, where h/H is proportional to d/D. With a pyramid he would have to know/measure the distance to the center of it, no?

@bjornkn said:

I was just curious if the Bosch lasers come with a level built-in, as I might be interested in buying one.

Mine does not. It's a PLR 30 (rather simple one) and it only measures to some 30 metres altogether.

OK. Strange that its specs doesn't mention that shortest/longest feature, while other Bosch lasers in the DLE series does mention it. I have borrowed a cheap "laser" too, but it apparently is only using the laser for pointing, and ultrasonic sound for measuring distance up to 12m

@tig said:

Alternatively by some decent surveying equipment

Good advice
Or, for more fun, speed and lower cost buy a decent plugin/app like PhotoScan
Although I'm a big PhotoScan fan I can see that a laser distance meter can be a very useful accessory too.
Those "laser glasses", is it just a pair of sunglasses with red glass, or does it have to be specifically made for "laser viewing"?

@tig said:

Also don't forget the 'Similar Triangle' method to get the height of something too tall to measure directly - this uses 'bright-sunlight' because it has to have a shadow - no gadgets required!

Nice, but it does require a vertical wall and a flat ground, which we rarely have here in Norway
Like this photo of our local fortress shows..
No flat ground, no vertical walls, and no right angles anywhere at all actually.

@roger said:

You did not fully understand the point of Gaieus' diagram and comments. As you sweep the meter up and down the distance reading will change. It starts out long reaches its shortest point and then gets long again. The angle where the distance is shortest is a perpendicular to the wall. When the distance is the shortest, you have a 90 degree angle between the wall and the laser line.

Yes, I understood that. Nice feature I was just curious if the Bosch lasers come with a level built-in, as I might be interested in buying one. Could be useful for measuring/calculating a longer reference, for use with tgi3D, than what is easily measured with a 5m tape measure. The longer the reference, the better the precision.
My Android phone has a built-in level (but the back side is slightly curved...) and I know that some laser devices are self-levelling, thus I wouldn't be surprised if the Bosch had a level too. And the iPhone probably have an app too?

Re. angles and measuring distances:
My question was how to calculate a height if the walls are not exactly vertical, based on only distance measurements from one position.
Gaieus' method will work for vertical walls, and the method with pointing upwards should work too, if there is something there to stop the beam, like a roof, or maybe a board laid on top of a fortress wall etc?
Like TIG explained you need the length of the 2 sides + the angle between them to calculate the third side. As long as the triangle does not have a 90 degree angle (like with a non-vertical wall) you cannot use only distances, but need one angle as well.

@Gaieus:
What is the model number of your Bosch?

IMO there's a big difference between a commissioned project (which should be charged per estimated hour) and a "free" image. And also if they want to license it for a single project, or to buy the copyright.
And there's also a difference between an image used for a commercial project like a brochure, and one used in a book, magazine etc.
I've never charged anything for books, magazines etc, except for one 3D/trueSpace image I made 15 years ago which apparently is still floating around on the net (just found it on Flickr! http://www.flickr.com/photos/49503103054@N01/3607124/in/photostream/ )
It was very small and old, so I charged around US$100 for it for use in a year book/report about a year ago.
If it was for an ad or something more commercial I'd probably have charged more.
For a larger/newer image I'd probably charge around $300-500? (and keep the copyright of course)

Is there a built-in level in the Bosch laser then?

@tig said:

While we are on 'formulas'...

If you know two sides of any triangle and the angle between them then you can find the length of the other side opposite that angle using the Cosine Rule

Exactly!
But you need to know one angle (which may be 90 degrees) and 2 sides to calculate the length of the third, right?
With only 2 sides and no angle you can't know the length of the third side?
But if the wall is vertical (90 degrees) you can calculate without using sin/cos, but just the a^2+b^2=c^2?

@roger said:

Bjorn, any triangle can be divided into two right triangles, each of which can be solved by pythagoras or sohcahtoa.

Yes, as long as you know some angles?
Or if you measure from 2 positions?

@Roger :
Afaik sin/cos/tan only works on right-angled triangles, and so do the Pythagoras rule a^2+b^2=c^2 - or here : a=sqr(c^2-b^2)
That's why I was so interested in the formulas in Gaieus' books. Too bad they are in the attic

BTW, did you get that iPhone theodolite to work with any precision?

@gaieus said:

That's true however the majority of buildings are (fortunately) rectangular/vertical (more or less). If not, we get out our secondary school geometry books again and do some calculations.
Wonder how those formulas look?

So what if the walls are not perfectly straight?
Lots of buildings have tapering walls, like Inca buildings, fortresses etc, and many have walls skewed by time/age and bad foundations, like the tower in Pisa etc.
Pythagoras won't help much then, will it?
I'm sure the Leica Disto D8 is a very useful tool, that can also do some angle measurements afaik, but will it be enough power/precision for such situations?
And with a price tag a lot higher (at least in this country ~US$1400) than the tgi3D/PhotoScan I know what I would have chosen But a cheap Bosch laser would probably be quite useful for measuring a reference distance. So far I have gotten enough precision with a 5m tape measure.

A bit OT:
A little while ago I saw a TV program from a volcanic rift (?) in Ethopia(?) where the team wanted to make a 3D scan of the extremely hot rift which puffed out toxic gases all the time. They rigged the laser scanner on a steel cable crossing the rift, and lowered it down to make the scan. They had to give up after a while, but they did get some parts of it 3D scanned. I can't help but smiling a little at their efforts, when they could have used the KISS principle and easily/safely gotten good results using PhotoScan (or similar software like PhotoModeler)

I second TIGs suggestion.
If there are anything that should be shortcutted in SU it is exactly those two commands (as well as show/hide hidden and X-ray).
I use H and Shift+H for those (and Shift+X and X for those others), and use them all the time.
You can also be inside a tool, like Move, and show/hide without having to leave the tool.
Very useful
And quite hidden if you rather want to avoid using shortcuts, as they're hidden inside the ModelInfo panel.

Very nice work
I'm not bothered by the flag, even though it is quite big.

But I am more bothered by the water in that night shot.
It looks like it is a reflecting a daytime cloudy sky instead of the actual scene?

Assigning a shortcut to "Make unique" would take you 10 secs, and 0.1sec every time you use it after a Move/copy.

When you import any DWG/DXF file into SU you need to tell SU which unit is being used in the file.
You don't have to do any conversion yourself, as SU will do it all for you.
It is no problem to import a file using inches into a model that uses cm (or whatever you're using), You just go into the Options and select Inches.
If you don't know the units used you could either try different units until you hit the right one, or just use the Tape Measure to scale it correctly. If in doubt I load the file into a DWG/DXF viewer first to look at some dimensions texts (which will not be imported into SU) etc.

I always thought (and have been told) that DWG does not store the unit type in the file.
None of the DWG/DXF viewers/converters I've been using have been able to read the units from the files. It is just numbers.

That a change of units in the dwg exporters results in a correct import into SU only shows that you happened to have your import units set to the same type as it was exported as.

All DWG files I've got from architects here in Norway use either mm (single buildings, plans etc) or m (site plans, terrains etc), which makes it quite easy to import correctly in the first place, once you know what the file contains. I usually prefer to use cm, which causes no problems at all in SU.

@TIG: Yes, the stave churches are great ! I had the pleasure of modeling one of them, including animated construction process, almost 10 years ago - for online art history education at the University of Bergen Pre-SU, but nice job..
And yes, Fred is indeed common on tombstones, or 'Hvil i fred' (Rest in peace), but we do have some Freds here too, as well as Fredrik and Freddy

I don't quite get this..
If the verticals are not parallel, which they obviously are not on the compared 2-point/zero tilt image , the camera does not have 0 tilt. ?
BTW, I typically use the 'position camera' to get 0 tilt, and then Walk to move back/forward and up down.
Works great too.

Thanks for the tip
Any idea what's the difference between the plain and Ti versions?
AFAIK the K in 2600K means that it is easy to overclock?

BTW, I get a 404 on that link..