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: Three GPS data comparison: All different. Huh?
    From: David Pike
    Date: 2021 May 25, 08:59 -0700

    I wish I’d read Frank’s explanation before pondering my own, which effectively comes to the same conclusion.  It’s probably the ‘firmware’.  GNSS receivers find their position by calculating the intersection of range spheres emanating from the satellites.  The don’t use elevation and azimuth.  These are ‘back-calculated, if you like, from the receiver’s position and the satellite’s ephemeris primarily for the benefit of researchers seeking explanation of anomalies in the quality of satellite ranges.  E.g., the satellite might be low on the horizon, or temporarily be hidden behind a building.  The receiver might be in the ideal position to temporarily receive signals bounced off a building in addition to the direct signals.  For most of us, such additional information is more for entertainment than strictly necessary.   Even researchers probably don’t need super accuracy in azimuth and elevation.  If they do, they’ll be using specialist analysis tools from the likes of Spirent.  This being so, calculating such additional information gets no more priority within the ‘firmware', than it deserves.  I've seen similar things while calculating the size of the Earth with school kids.  Distance gone on a handheld GNSS receiver odometer rarely exactly matches the accompanying trundle wheel value.  So, was it the sweet little thing reading the handset upside down or the cute kid determined to beat the world trundle wheel racing record. DaveP

    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