-------- Original Message --------
Subject:        Re: average world wide elevation
Date:   Mon, 25 Aug 2008 14:02:49 GMT
From:   [log in to unmask] <[log in to unmask]>
To:     [log in to unmask]



Oops....I looked at this:

More information on each of these sources is provided in section 6.1
(Data Sources).  The cells with value 0 (ocean) in the source map can
be used as an ocean mask (the ocean cells match exactly all the cells
masked as "no data" in the DEM with a value of -9999).  Likewise, the cells with values 1-8 together constitute a global land mask.  Every cell in the DEM with an elevation has a corresponding cell in the source map with a value in the range 1-8.

So it looks like water has already been masked out.

You'd still want to project the tiles to equal area though.  However the task is now considerably easier.  However a pixel at the top of a 50 degree by 50 degree tile is not the same area as a pixel at the bottom of a 50 degree by 50 degree tile.  You would also need the amount of land within each tile to get a proper average (that could be gotten with an overlay on any digital world map).

Joe McCollum
Information Technology Specialist
Forest Inventory and Analysis
Knoxville TN  37919



-- Maps-L Moderator <[log in to unmask]> wrote:
------- Original Message --------
Subject:        Re: average world wide elevation
Date:   Sun, 24 Aug 2008 07:49:33 -0700
From:   Matt Fox <[log in to unmask]>
To:     [log in to unmask]
References:     <[log in to unmask]>



There is a chart near the top of this page that lists the mean elevation
for 27 sections of the earth.  Shouldn't be hard to figure out an
average/mean from there.

http://www.npagroup.com/catalogue/shop/gtopo30/gtopo30_readme.htm

Matt


On Fri, Aug 22, 2008 at 11:02 AM, Maps-L Moderator <[log in to unmask]
<mailto:[log in to unmask]>> wrote:

    -------- Original Message --------
    Subject:        average world wide elevation
    Date:   Fri, 22 Aug 2008 13:55:46 -0400
    From:   Lisa Sweeney <[log in to unmask] <mailto:[log in to unmask]>>
    To:     [log in to unmask] <mailto:[log in to unmask]>



    Someone was asking for the average elevation above MSL (mean sea level)
    of land worldwide.
    If any of you know the answer or have a favorite source for this type of
    questions please share.

    thanks
    lisa

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