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    Re: Where am I?
    From: Bruce J. Pennino
    Date: 2013 Sep 29, 23:50 -0400
    
    Hello:
     
    I'll give a brief response now and maybe  more later. My background is a civil engineer that has done a modest amount of construction layout, taught basic surveying for years, and now using a Topcon 2 ST? model to measure dip angles and determine my location. I gave up on trying to use  the sun because I could not easily attach or make a proper filter (no distortion). With reasonable care you can easily use a theodolite to get with 1,500 ft....infact I've gotten to less than 1,000 ft, but maybe lucky.
     
    Use the moon and Venus ; you don't need a horizon. Use standard sight reduction procedures with no dip because I assume your theodolite gives zenith angles. You can easily see Venus in south west at dusk (low angle) and the moon is available for 14 days/30, more or less.  There are several  bright stars that also work. If you find an older surveying book, there are long discussions on various techniques.  Find a Wolf , Elementary Surveying, prior to 1990, maybe 1980 or 1970 is even better.  With a book from the 1930s or 40s, even more detailed procedures. It can be done with a transit by repeating angles etc to increase precision and accuracy.  If you really want to do it in a historical elegant  fashion, Gurley made some incredible  astronomical transits. But these are rare and normally in private collections. I've never seen one except in museums. It helps if you have a 90 degree eyepiece prism (or whatever it is called) so you are not limited to angles of 30-35 degrees Hs (60deg or so zenith).

    Bruce
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
    ----- Original Message -----
    From: rgaarden
    Sent: Sunday, September 29, 2013 6:41 PM
    Subject: [NavList] Where am I?


    Hello,
    I have perused posts located by searching "theodolite" and understand that using a theodolite for astronomical geolocation is in the dust bin. None the less, I am an amateur surveyor who first became somewhat obsessed about finding North within 20". For me, not an easy task. Now I want to know where I am on earth. I would like to use observations of the Sun. I have done this with a sextant and found that working with sights in a tub of water is not for me. My results vary enough that when I have a result within a few nautical mile of my known location, I know it was largely luck. The theodolite is stable and I have come to trust my work with it. Would someone point me to a procedure for using a theodolite to establish longitude and latitude? I am not asking for hand holding but a well documented procedure would be gratefully received.
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