Welcome to the NavList Message Boards.

NavList:

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

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    Name or NavList Code:
    Email:
       
    Reply
    Re: Horizontal Sextant angles plot.
    From: Richard B. Langley
    Date: 2012 Apr 6, 08:47 -0300

    GPS receivers determine their velocity vector from Doppler shift
    measurements not a succession of positions. Quoting from my article
    "The Magnetic Compass and GPS":
    
    "A GPS receiver can provide accurate information about its position
    and velocity, and from the velocity vector it can determine the
    direction in which it is moving - called the course or track. The
    accuracy with which a receiver can compute this direction depends on
    its speed (the velocity magnitude) but is usually better than one
    degree for speeds greater than about 10 kilometers per hour. The
    course is not necessarily the same as the heading or direction in
    which the GPS receiver, or the platform on which it is mounted, is
    pointing. A single-antenna GPS receiver cannot determine heading.
    However, a compass can provide this information and as mentioned
    earlier, some GPS receivers incorporate an electronic compass, usually
    a two-axis sensor. Some receivers have three-axis sensors that give
    relatively accurate bearings even if they are slightly tilted."
    
    The article can be found here:
    
    http://www.gpsworld.com/gps/the-magnetic-compass-and-gps-828
    
    -- Richard Langley
    
    Quoting Alexandre E Eremenko :
    
    >
    > Lu,
    >
    >> The problem with "GPS as compass" is that GPSs can only determine position.
    >> Everything else that a GPS might show (especially direction of
    >> movement) is derived from a succession of positions.
    >
    > This was exactly what I thought when I was shown this "GPS compass".
    > One was supposed to turn the GPS device (like a compass) in certain
    > direction and it told you the asimuth of this direction...
    > with the error of sevral 10's of degrees:-)
    >
    > (I did not even need a compass to see this, an analog watch and the
    > Sun was enough).
    >
    > I imagine some people who believe in technology, carry only GPS
    > with them, and use this info without even looking at the Sun:-)
    >
    > Alex.
    >
    >
    >
    >
    
    
    
    -----------------------------------------------------------------------------
    | 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/       |
    -----------------------------------------------------------------------------
    
    
    
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

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

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

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

    Email Settings

    NavList ID Code:

    Custom Index

    Subject:
    Author:
    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