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: Longitude shift on NOAA charts vs. Google Earth
    From: Lu Abel
    Date: 2012 Aug 14, 11:32 -0700
    With respect, Gary, I don't think the NAD27 to WGS84 shift can explain the 1/4 nm (1500 ft) shift George reports.  It's on the order of a few hundred feet in most places in the continental US. 

    I just double-checked -- the chart for Narragansett Bay in Rhode Island says that the NAD-24 to WGS-84 shift is 0.3 SECONDS in latitude, 1.8 SECONDS in longitude.   The San Francisco Bay chart lists 0.3" for latitude, 3.9" in longitude.   Even using the SF Bay value, that's 1/15 of a nautical mile (or about 400 ft), not the 1/4 mile George is seeing.

    George, where location does your chart cover?

    From: Gary LaPook <garylapook@pacbell.net>
    To: NavList@fer3.com
    Sent: Tuesday, August 14, 2012 10:33 AM
    Subject: [NavList] Re: Longitude shift on NOAA charts vs. Google Earth

    The datum of your chart is most likely NAD 27 (North American Datum of 1927) and Google Earth uses a different datum, WGS 84.


    --- On Tue, 8/14/12, G Becker <george@gwbeckerpls.com> wrote:

    From: G Becker <george@gwbeckerpls.com>
    Subject: [NavList] Longitude shift on NOAA charts vs. Google Earth
    To: NavList@fer3.com
    Date: Tuesday, August 14, 2012, 8:37 AM

    Sorry if this has been covered before.. On my office wall I have an older NOAA chart (1979). I mark the Lat/Long of various sites on the chart using data from Google Earth. The marks are made in alignment with the NOAA chart scales found around the border. Comparing the two versions of Lat/Long, Google's data is always shifted approximately 1/4 Nautical mile toward Greenwich. Latitude is always accurate. If my data is not incorrect, what would be the difference in the two Lat/Long systems?
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com

    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