-------- 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 -- ********************************* Head, GIS Services, MIT Libraries http://libraries.mit.edu/gis/ 617-258-5598