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: Uk data
    From: Frank Reed
    Date: 2021 Jun 30, 10:03 -0700

    "easting and then northing"

    There is a logic to this choice, and it can be summarized with one, very familar shorthand: (x,y).

    Standard, traditional cartesian coordinates which we all learn in school are x,y coordinates, and in the usual, nearly universal display of those coordinates "on a page" x is horizontal, increasing to the right on the page, and y is vertical increasing up the page. Given this traditional and almost ubiquitous orientation of coordinates, when carried to geographic coordinates, differences in longitude become x values, differences in latitude become y values, and positive x is to the right, positive y is up. Thus (x,y) becomes (easting,northing) and east and north are positive directions. 

    Note that these choices of ordering and positive directions are not "laws" of mathematics. They are conventions. But they're extremely common conventions, and that's why it makes sense to apply them in geography. And it's not just antiquated systems like grid coordinates. You'll find the same ordering, for examplle, in the Google Earth standard data format known as KML.

    I'm attaching a KML of a circle of position for a Sun local noon sight taken from the vicinity of Mystic Seaport Museum on the summer solstice. You can download this file, and then if you launch it ("double click it"), it will open in your KML viewer which should be Google Earth unless you have not installed Google Earth (and if not, why not?!). You can also open this file in a common text editor. If you open "options" on the downloaded KML file ("right click it"), then you can open it in a text editor, and you will see that it is quite simple inside. There are about 25 header lines, which you can ignore, followed by a long list of lon,lat pairs. If you scroll down far enough, you will find the pair -71.9800,41.3610. That's a longitude of 71.98°W and a latitude of 41.361°N ...lon comes first, W is negative, N is positive, following traditional (x,y) coordinate convention.

    Frank Reed

    File:


       
    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