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I still teach sun shots to our geomatics engineering students.
-- Richard Langley

Quoting G Becker :

> Geoffrey:
>
> I have only the vaguest knowledge of land surveying techniques, but
> I am forced to ask two questions:
>
> 1.  Do land surveyors do astronomical observations to establish
> position any more?   Every surveying crew I observe these days seems
> to have one of these high-precision GPS devices.   In fact, did they
> ever do it except, for example, to establish the position of some
> island in the Pacific?    Every illustration of surveying techniques
> I've seen seem to be based on distances and angles from known
> starting points (called, I believe, traverses).  The Great Survey of
> India, a 60-year effort to map the boundaries of the subcontinent,
> was strictly trignometric; if celestial observations were part of
> the surveyor's repitorie, would they not have been used here?
>
> 2.  If land surveyors were to attempt to do high-precision location
> via celestial sights, would they use the NA for celestial data or a
> publication giving celestial data to even higher precision?
>
> We're talking about the Nautical Almanac, which is intended for
> celestial navigation of ships.  I suspect an almanac with data that,
> with perfect observations, gives location to within 0.1 nautical
> mile is quite sufficient for the task.
>
>
>
>
>
>
> Lu,
>
> I just deleted a long diatribe on the state of Land Surveying
> today... instead, I'll attempt to answer to your two questions. By
> the way, I'm a licensed land surveyor.
>
> 1a. No. when they seldom did, this was the reference ephemeris (
> http://www.rollanet.org/~eksi/Handbook.htm )2008 was the last year
> published.
>
> 1b. Yes. Usually via a sun shot. The software in my data collector
> has a sun shot option built in. The problem with modern total
> stations is they suggest you not point it toward the sun due to the
> delicate optical electronics. (go figure, maybe a sales ploy)
>
> 1c. I'm not familiar with the India Survey.
>
> 2a. See 1a.
>
>
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| Richard B. Langley                            E-mail: lang@unb.ca         |
| Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/ |
| Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142   |
| University of New Brunswick                   Fax:      +1 506 453-4943   |
| Fredericton, N.B., Canada  E3B 5A3                                        |
|        Fredericton?  Where's that?  See: http://www.fredericton.ca/       |
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