Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Leap second today
    From: Geoffrey Kolbe
    Date: 2012 Jul 02, 18:12 +0100

    At 16:42 02/07/2012, you wrote:
    >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?
    I could respond by asking if professional sailors 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?
    Ah yes, but you need to know the azimuth angle of those traverse
    lines. And using a theodolite to do a timed observation of the sun to
    obtain a reference azimuth is a very quick and accurate way of doing
    it - even in these days of highly accurate GPS receivers. The NA is a
    very available and very suitable ephemeris for doing such work.

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site