Re: [ferret_users] how to plot border between land and sea

[Pooran khedri <pooran.khedri@xxxxxxxxx>]

Thank you so much for your response,

I changed the land values to -1, and run the command, countour/lev=(0) depth

But I couldn't plot the border between sea and lands,

Any suggestions would be appreciated, 

Regards,

Pooran

On Sat, Dec 25, 2021, 3:49 PM Ryo Furue <furue@xxxxxxxxxx> wrote:

Dear Pooran,

I have a bathymetery data which contains positive values for depths and zero for land regions. I need to plot borders between see and lands.

I don't think of a clean way.  One idea is to assign a negative value, say −1 m, to land and plot the contour lines corresponding to depth = 0.  If you do that, the contour lines tend to be significantly different from the real coast lines.  This is because we miss the actual altitude data of the land.

So, a better way may be to plug in real land topography data to the land points of your depth data.

set data ETOPO5

let alt_regridded = rose[gx=depth,gy=depth] ! positive for land

let  dep_ocean_land = if depth ge 0 then (-1)*alt_regridded else depth

contour/lev=(0) dep_ocean_land

If your depth data and the topography data don't match, the above method may result in some noisy coast lines.

Ryo