Quote:
Originally Posted by AstroJunk
I was out with a surveyor one time and for fun we punched a few Alt-Az coordinates of bright stars into his theodolite and he was gobsmacked  |
As a student long ago in my spare time I worked as a chairman for a surveyor, and one day out in the bush we did the same as a means of determining position directly from stars in daylight (I knew the spherical trig maths). We did a whole series of measurements on each of 4 stars and set up our own reference point. From memory we used precision clock timings as stars crossed micrometer lines in the telescope either side of the meridian to determine longitude, and for latitude, used the altitude as they cross the meridian. The USNO almanac provided corrections due to refraction and precession etc.
Theres also the "surveyors formula" to determine long & lat directly from the alt & az of two stars, corrected for refraction & precession and the time difference between the measurements, though not as good as the above method.
Both worked quite well when compared with measurements from distant trig stations, and he was most impressed.
A few years later when Dave Herald was organising Bailey's Beads timing at solar eclipses, if you had good data USNO would subsequently visit the site to do an astrometric survey to determine your position using the same methods.
This was long before the advent of GPS, obviously.
