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
    or...
       
    Reply
    Re: As we debate GPS reliability
    From: Frank Reed
    Date: 2009 Nov 13, 21:38 -0800

    Lu, you wrote:
    "Although it's not exactly clear what the fourth dimension is (Jeppsen says 
    it's time, but then doesn't give an example of exactly how time figures in)"
    
    4D navigation is all the rage in air navigation today. For air traffic, it 
    makes a lot of sense since it's about saving fuel. A traditional flight from 
    one city involves a climb at some fixed rate to cruising altitude, a cruise 
    at that altitude, and then a descent to the destination airport. Supposedly, 
    this 4D type of navigation creates continuous contours in space and time 
    taking advantage of winds and the exact behavior of the aircraft's engines 
    and aerodynamics that can significantly increase fuel efficiency. Heck, 
    you'll arrive at the gate with just one drop of fuel left in the tanks (!!). 
    Marine navigation can be highly optimized to take advantage of currents and 
    avoid bad weather in order to reduce transit time as well as fuel 
    consumption. Some of this is simple, and there's already a lot of software to 
    do this. It's not so different from a road mapping program that finds the 
    quickest path to your destination by putting you on the highway just to get 
    across town even though your "instincts" might prefer a straighter path. 
    
    I do await the day when a dozen boats all running the same software converge 
    on the same offshore point simultaneously. I realize that software designers 
    think of these things and write code with such issues in mind, but then there 
    are those inevitable things called "bugs". I'm also waiting for a boat to 
    turn up in Portland, Oregon instead of Portland, Maine.
    
    -FER
    
    
    
    
    --~--~---------~--~----~------------~-------~--~----~
    NavList message boards: www.fer3.com/arc
    Or post by email to: NavList@fer3.com
    To unsubscribe, email NavList+unsubscribe@fer3.com
    -~----------~----~----~----~------~----~------~--~---
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    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:

    Email Settings

    Posting 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