Re: [ferret_users] Sea area demarcation

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi -
If you want to flag your data according to whether it's over land or 
sea, you can use a topography/bathymetry data set as Ryo suggested, and 
create a land/sea mask. There are a couple of higher-resolution data 
sets I know of which are available via DODS.  For example using the 
ETOPO 5-minute data set, we can make a mask which is 1 where there is 
water, and missing over land.

 set data "http://www.ferret.noaa.gov/cgi-bin/dods/nph-dods/data/etopo5.nc";
 let mask = if rose lt 0 then 1
 shade mask

! To work with this and your data, regrid the mask to the grid of your 
data, and multiply.
! If your data were in a file called my_data.nc, and a variable called var:

 cancel data/all

 set data "http://www.ferret.noaa.gov/cgi-bin/dods/nph-dods/data/etopo5.nc";
 set data my_data.nc

 let mask = if rose[d=1,gxy=my_var[d=2]] lt 0 then 1
 set region/x=80w:55w/y=65n:80N

 shade mask * var

For finer detail, I was going to suggest the Smith-Sandwell data, which 
is available via DODS, but this data set does not go farther north than 
72 degrees.  Does anyone on the list have a suggestion for topography 
data in the far north?

 set data 
"http://ferret.pmel.noaa.gov/cgi-bin/dods/nph-dods/data/PMEL/smith_sandwell_topo.nc";

Ansley

Juanxiong He wrote:

> Dear all,
> I would like to know where I can find the sea area demarcation data, 
> such as the boundary line between Arctic Archipelago and Baffin Bay. 
> It's a terrible thing to using eyes identifying the boundary line poin 
> by point.
>
> Thanks in advance!
>
> Herring