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

Contents

[edit] 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)

[edit] 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)

[edit] Setting Circle(s)?

A question for the experts in this field. I have been editing the page Setting circles and have come across this reference:

....Answers.com the "McGraw-Hill Dictionary of Scientific and Technical Terms":
setting circle (′sed·iŋ ′sər·kəl)
(engineering) A coordinate scale on an optical pointing instrument, such as a telescope or surveyor's transit.

Is the graduated scale on a Theodolite ever call a "Setting circle"? If so it looks like the Theodolites should be mentioned in that article and "Setting circle" should be mentioned in the Theodolite article. Halfblue 00:03, 22 January 2007 (UTC)

[edit] Theodolite in manufacturing

Can anyone describe a manner in which theodolites are used in precision manufacturing? I just heard that it used in conjunction with tooling balls for precision measurements.

I appreciate any comments. --Dchem 16:05, 1 June 2007 (UTC)

While I've seen them on shop floors (aircraft manufacturing) I can't give details on their use specifically. They have also been used in assembly of launch vehicles by NASA in the '60s - the alignment of various Titan and Saturn rockets used them; I saw this recently in a documentary on the Apollo program. These days they'd be able to use laser-based systems instead, I suppose.
One of the more interesting uses I've seen was in a chemistry lab at a university (research, not manufacturing). A transit (older, early 20th c) theodolite was set up on one side of the lab. A chemical process that gave off a gas was being investigated. The gas was vented through a long, vertical, glass pipe. Inside the pipe, a fine, glass coil spring was hung with a small glass plate on the lower end. Since the (initially very clean) glass would absorb the gas on its surface, the weight of the gas would cause the spring to lengthen. The theodolite was used to measure the displacement of the glass plate and that deflection was, in turn, used to determine the amount of gas absorbed on the glass spring + plate. Michael Daly 17:14, 6 October 2007 (UTC)

[edit] 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)

[edit] 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)


[edit] 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)