Talk:Theodolite

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Ah! Somebody else writing about theodolites :-)

Too bad the article is so limited. Right angle, or bent path, theodolites were used extensively in meteorological observations of winds aloft. The PIBAL (pilot balloon) was tracked with a theodolite and winds were calculated by measuring azimuth and elevation of the balloon at fixed, usually one minute, intervals and by knowing the ascent rate of the balloon (balloons were filled to a precise amount of lift). Although not used to any great extent today, balloon soundings are still taken to a limited extent.

JET

please,show the setting up of the theodolite

Gyro-Theodolite

I have just created this article as a request on WP:AFC. Please have a look at it and see if it warrants an article on its own or if it would better be merged into here. Also if you know anything about it, feel free to expand it.and to see the moon.

I have just expanded the gyrotheodolite section and removed the misleading paragraph. Maybe it needs a new page --King of Tea Tree (talk) 11:03, 24 January 2008 (UTC)

How can this be?

Here's the thing: the page says a theodolite combines a telescope with measuring technology, and was invented in 1571. I thought the telescope made its appearance in 1608! I know Digges is said to have constructed a telescope, but that was a reflector; can't be what we're talking about here...so what's the solution to this discrepency?

Perhaps it is incorrect to imply that the telescope is a necessary component. The instrument could perform all of the same functions (albeit, with lower precision) if it were equipt with a non-telescopic aiming sight. I would be interested in seeing the Digges model.

219.78.135.245 09:07, 5 July 2007 (UTC)

A theodolite is a precision instrument used for measuring angles in horizontal and vertical planes. While theodolites are commonly associated with surveying and construction, they can also find applications in manufacturing processes. Here are a few ways theodolites can be used in manufacturing:

Alignment and Positioning: Theodolites can be used to align and position large machinery or equipment accurately. For example, in manufacturing plants where precision is crucial, such as automotive or aerospace industries, theodolites can help align components during assembly or ensure accurate placement of molds and tooling.

Quality Control and Inspection: Theodolites can be used for quality control purposes, verifying the dimensional accuracy of manufactured parts. By measuring angles and distances, theodolites can help assess the alignment, straightness, and flatness of surfaces, ensuring they meet the required specifications. This is particularly useful in industries where precision and tight tolerances are critical, such as the production of turbine blades or optical components.

Geometric Measurements: Theodolites can assist in measuring various geometric parameters, such as angles, distances, heights, and elevations. These measurements can be useful for verifying the geometry of components, ensuring they conform to design specifications. Theodolites can be employed to measure the angles and alignments of features on manufactured parts, checking for deviations or verifying proper assembly.

Calibration: Theodolites themselves need to be calibrated periodically to ensure their accuracy. In manufacturing settings, theodolites may be used as part of the calibration process for other equipment or instruments. For example, in coordinate measuring machines (CMMs) used for precise dimensional measurement, theodolites can be employed to verify and calibrate their performance.

Overall, theodolites offer a means to measure angles and distances with high accuracy, making them valuable tools in manufacturing processes that require precision, alignment, and quality control. Their versatility and ability to provide precise measurements make them suitable for various applications, aiding in efficient and reliable manufacturing operations Jual Theodolite Digital.

Confused history.

The history section states that the theodolite derives from the plane table alidade. Since the plane table dates to the 17th century and Digges described the theodolite in 1571, there's an obvious discrepancy. The theodolite derives from prior instruments such as the geometric square and various graduated circles and semi-circles.

BTW - Leonard wrote the book, his son Thomas published it posthumously. The full title is A geometric practice named Pantometria.

Digges was preceded by Gregorius Reisch who described such an instrument in Margarita Philosophica, Strasburg, 1512.

This section needs a serious re-write. I'll be back! :-) Michael Daly 22:13, 5 October 2007 (UTC)

Accuracy

The article says theodolites could meassure "angular scales accurately to within a second of arc" since several centuries ago. I doubt this is true but I'm not sure, some modern theodolites aren't that accurate.--200.125.48.41 14:54, 17 October 2007 (UTC)

That is a comment on Jesse Ramsden's dividing engine, not theodolites in general. When manufacturing the graduated limb, the errors in the markings are less than a second of arc. Michael Daly 16:27, 17 October 2007 (UTC)

Sextant vs Theodolite

Apologies in advance. What is the difference between a "Theodolite" and a sextant? "Theo" itself seems a little pretentious, being God and such, at least in it's "Theo's" incarnation. Isn't it actually Mr. Everest's own named "Sextant" that helped the fine fellow measure the Great Mount? —Preceding unsigned comment added by 76.171.75.225 (talk) 06:25, 22 April 2008 (UTC)

A sextant measures angles on one sixth of a circle. For simple sextants, such as astronomical sextants, that means the angle measured is up to 60°. For double-reflecting sextants such as navigator's sextants, the angle measured is up to 120°. The orientation of the sextant can be varied in many cases from horizontal to vertical. In general, a simple navigator's sextant can measure with limited accuracy of about one-fifth of a degree.

A theodolite is a more sophisticated instrument that will simultaneously measure both a horizontal and a vertical angle through a full 360°. The two degrees of rotational freedom of the instrument are fixed at right angles and so arbitrarily oriented angles cannot easily be measured directly. The accuracy can be greater than a sextant of comparable size. However, the theodolite must be carefully levelled on a tripod or other mount and is not hand-held. One thing that a theodolite can do is be positioned over a specific point on land with considerable accuracy.

Sextants and theodolites can be used interchangeably, but the ease of use for a specific purpose will differ. A tripod-mounted theodolite on the deck of a ship will make for a poor navigation instrument and a sextant in many geodetic or construction tasks will be tricky to use. --Michael Daly (talk) 21:44, 24 April 2008 (UTC)

Tachometer or Tacheometer

A tachometer measures speed of rotation, a tacheometer measures quickly. I have changed the spelling in article. King of Tea Tree (talk) 23:24, 28 July 2008 (UTC)

Concept of Operation doesn't explain operation!

This article does a poor job of explaining how a theodolite is actually operated. For example, in the introduction, the text states "when the telescope is pointed at a desired object, the angle of each of these axes [horizontal and vertical] can be measured with great precision, typically on the scale of arcseconds." Apart from the inaccuracy in the description (the angles measured are the angle between the object's line of sight and two perpendicular planes -- presumably the horizontal plane and a vertical plane through a meridian), how is the horizontal plane established? Is there a spirit level built into every theodolite? Later, the article mentions plumb bobs and levels but doesn't clearly establish how they are used. Similarly, is the angle in the horizontal pane determined by a compass that determines magnetic north? i.e., is there a compass built into every theodolite? The "concept of operations" doesn't say. Ross Fraser (talk) 22:52, 17 May 2009 (UTC)

While the article isn't the model of clarity, I'll just point out that all theodolites have a spirit level to establish a horizontal reference. The legs of the theodolite are adjustable (the legs in the base of the theodolite where it sits on the top of the tripod) and thumbwheels are used to adjust their lengths to bring the base into level.

Plumb bobs and optical plummets are used to establish a vertical line through the centre of the theodolite that is over a point on the ground. This establishes the position on a horizontal plane (e.g. the Earth's surface, say, in a field) about which the theodolite rotates. Once level, vertical angles are measured relative to the horizontal.

Horizontal angles are relative. One has to establish a baseline reference and then measure the angle relative to that. Some older theodolites have compasses in them. However, there are usually other points of reference that are used. Geodetic reference points (aka triangulation points) are established throughout most jurisdictions; they can be used to provide references to known locations. For example, in the city where I currently reside, there are small circular brass markers embedded in sidewalks at various locations. On the brass marker, a large triangle denotes its use as a horizontal triangulation point (as opposed to a vertical elevation reference point). The exact reference point is an indented mark, a couple of millimeters in diameter at most, that is placed on the marker by a geodetic surveyor. Connecting two such points, usually no more than a couple of blocks apart, establishes a well-defined baseline. --Michael Daly (talk) 03:56, 18 May 2009 (UTC)

Wrong? Caption in Concept of Operation might be off

The Caption in Diagram of an Optical Theodolite says that the vertical angle is 94deg, 12min, 44sec.

I think it should be 94deg, 02min, 44sec. —Preceding unsigned comment added by 199.46.200.232 (talk) 16:51, 10 May 2010 (UTC)

You're correct, it would appear. However, that text is in the image and can't be changed without modifying the image. This typo, according to the image's accompanying documentation, appears to be in the US Army manual. --Michael Daly (talk) 21:52, 13 May 2010 (UTC)

Some of these definitions incorrect?

In particular, the sentence:

In the middle of the 20th century, "transit" came to refer to a simple form of theodolite with less precision, lacking features such as scale magnification and micrometers.

The instrument known as the engineer's transit was the same from maybe the 19th century until electronics took over. It was as described in the above sentence. A theodolite was always the high-precision version of a transit, which sometimes was unable to "transit" the telescope. There were further breakdowns of these general terms. Tfr000 (talk) 22:23, 30 May 2012 (UTC)

See, for instance,

http://books.google.com/books?id=HelMAAAAYAAJ&pg=PA264&source=gbs_selected_pages&cad=3#v=onepage&q&f=false

http://books.google.com/books?id=qJgIAAAAIAAJ&pg=PA105&source=gbs_selected_pages&cad=3#v=onepage&q&f=false

Tfr000 (talk) 12:50, 31 May 2012 (UTC)

I suspect that the quoted sentence came about because the middle of the 20th century is when high-quality, high-precision optical theodolites of European manufacture (brand name Wild) started to be widely used in America, rather than the other way around. Tfr000 (talk) 13:23, 31 May 2012 (UTC)

See:

http://books.google.com/books?id=PeADAAAAMBAJ&pg=PA138&dq=wild+theodolite&hl=en&sa=X&ei=_XDHT8KIH8fl0QHMrqDHDw&ved=0CEoQ6AEwAA#v=onepage&q=wild%20theodolite&f=false

Tfr000 (talk) 13:29, 31 May 2012 (UTC)

Apparently, in Europe, the term is theodolite for all of these instruments. The distinction between transit and theodolite seems to have been an American thing. Tfr000 (talk) 15:30, 31 May 2012 (UTC)

Looking back through the edit history here, it seems the article used to be more clear on these points:

The transit refers to specialized type of theodolite that was developed in the early 19th century. It featured a telescope that could "flop over" ("transit the scope") to allow easy back-sighting and doubling of angles for error reduction. Some transit instruments were capable of reading angles directly to thirty arc-seconds. The role of transits diminished in the late 20th century with the advent of compact, accurate electronic theodolites.

Probably we should restore this to make it more understandable. As is, it reads like the term "transit" for a lower-precision theodolite came around mid-20th-century, when in fact that's what it stood for all along. Tfr000 (talk) 18:26, 31 May 2012 (UTC)

Interesting (new) source

Insley, J.; (2008) The Tale of the Great Theodolites. Londen: Science Museum. Sander1453 (talk) 08:26, 6 October 2013 (UTC)

Not quite correct.

In the description, it says, "The builder's level is sometimes mistaken for a transit theodolite, but it measures neither horizontal nor vertical angles". However, most all levels, both Dumpy and automatic will measure a horizontal angle, (some pretty precise), just not a vertical. They are single axis, but will measure angles about that horizontal axis.--Craxd (talk) 02:01, 15 May 2014 (UTC)

This sorted Dougsim (talk) 11:17, 10 August 2018 (UTC)

Metrology?

The lead states that theodolites are used in metrology, but this is not mentioned in the body of the article. I have a little knowledge of the subject matter, and I think this might mean meteorology, where, for example, theodolites are used in tracking weather balloons. Either way, if it's mentioned in the lead, it should do so only to highlight its mention in the body of the article. Lou Sander (talk) 22:52, 24 May 2014 (UTC)

They're used in metrology too. It's not common, as it falls somewhere between dedicated instruments in jigs and modern coordinate measuring machines. However theodolites are cheap (compared to custom optics) and capable. An interesting example from the 1920s was the GWR locomotive works at Swindon, which invested in a Zeiss custom system for aligning locomotive frames. This gave significantly better performance (and in turn, reliability) for GWR locomotives. In comparison the LNER had perennial problems with the Gresley conjugated valve gear where less-good alignment led to imbalance between cylinders and overloading of the middle cylinder. Theodolites were used for the erection and fitting of large machinery installations around this period, notably in shipbuilding for engine installation and the alignment of turbine generator sets in the first steam turbine power stations. Andy Dingley (talk) 10:54, 25 May 2014 (UTC)

Great stuff, but it's not in the body of the article. That's my point. (Also that maybe meteorology isn't mentioned.) Lou Sander (talk) 16:53, 25 July 2014 (UTC)

Since posting the above, I added a referenced section on weather balloons, and took the liberty of changing "metrology" to "meteorology" in the lead. I would welcome the addition of a metrology section to the article, and the re-addition of the lead's reference to metrology. I'm also going to remove the "more references" tag on the article, since there are plenty of them now. Lou Sander (talk) 17:52, 25 July 2014 (UTC)

Zenith angles

The article describes angles between the zenith and the target as vertical angles. This is wrong. These are zenith angles. A vertical angle is an angle between the horizon and an object. A vertical angle can be positive of negative. Theodolites measure these and forward and reverse. For example a target at the same altitude as the instrument would be measured as 90 and 270 degree (both positive) zenith angles. This should be corrected in the article. Senor Cuete (talk) 20:29, 8 December 2016 (UTC)

Some definitions from the glossary of the Astronomical Almanac Online:

zenith distance: angular distance on the celestial sphere measured along the great circle from the zenith to the celestial object. Zenith distance is 90° minus altitude.

altitude: the angular distance of a celestial body above or below the horizon, measured along the great circle passing through the body and the zenith. Altitude is 90° minus the zenith distance.

"Vertical angle" would seem to be an umbrella term that could cover either measurement. Jc3s5h (talk) 20:52, 8 December 2016 (UTC)

That's correct as per Glossary of the Mapping Sciences: "angle, vertical - An angle in a vertical plane. Also called a gradient (Brit.). In surveying, one of the sides of a vertical angle is usually either (a) a horizontal line in the vertical plane or (b) a vertical line in that plane. In caso (a), the angle is then called, also, the angular elevation or angular depression or altitude. In case (b), it is also called the zenith angle." [1] fgnievinski (talk) 01:30, 7 January 2017 (UTC)

Do you have a source supporting your definition? Do you have a source stating that all, or nearly all, theodolites operate as you describe? Jc3s5h (talk) 20:52, 8 December 2016 (UTC)

OR: I've never seen one during my career as a surveyor that didn't use zenith angles. I couldn't have passed the surveyor exam without knowing this and the illustration shows this. Back at you: can you show me a theodolite that measures them any other way?Senor Cuete (talk) 21:51, 10 December 2016 (UTC)

I've only handled a few theodolites, and as best I can recall, they used zenith angles. But I hesitate to extrapolate from US experience to the world-wide situation. Jc3s5h (talk) 22:31, 10 December 2016 (UTC)

If the scale reads near 90 degrees at the horizon it is marked in zenith angles. Theodolites generally measure zenith angles, but I don't know that to be an absolute rule. Transits generally measured angles from the horizon, and were called vertical angles but I think either falls under the general term of measuring with the vertical motion.

Please undo the recent edit. First of all, that detail doesn't belong at that point in the article.

Secondly, you are confusing the what the terms describe. The diagram is correct. The terms describe the axes, which are the opposites of what is being measured by motion on them. The motion that allows you to move the telescope up and down is about an axis that is horizontal, the trunnion axis. The motion that lets you measure angles right and left is about an axis that is vertical, as labeled in the diagram. BillHart93 (talk) 06:01, 6 January 2017 (UTC)

So what I wrote here and in the article is correct but you want to move it? Theodolites do measure zenith angles but it's possible that somewhere there's an instrument that measures vertical angles but no one has ever seen one? When one turns up the article could say this. Senor Cuete (talk) 16:49, 6 January 2017 (UTC)

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Child articles re-merged and deleted?

Should Temporary adjustments of theodolites and Permanent adjustments of theodolites be deleted and appropriate content merged back into this article? These two pages seem like how-to articles; I can't find any other articles in WP about how to make adjustments to a piece of equipment. Wanted to ask other editors for their thoughts as a first step. Thanks. Levivich (talk) 22:47, 15 January 2019 (UTC)