How to filter out the elevation higher than 0

Hello all,

I wrote my code to get the elevation of the Cape Fear Area to make a mesh grid.

I wanted to know if there is a way to filter out any elvation higher than 0.

filename = 'crm_vol2.nc';
meta = ncinfo(filename);
disp('Variable List');
names = {meta.Variables.Name}'; 

% there are 3 variables inside the netCDF file: x, y, z
x = ncread(filename, 'x');
y = ncread(filename, 'y');
z = ncread(filename, 'z');
z = z';
min_x = min(x);
max_x = max(x);
min_y = min(y);
max_y = max(y);
dxy = 8.3333e-04;
[xv, yv] = meshgrid(min_x:dxy:max_x,min_y:dxy:max_y);

dx = dxy;
dy = dxy;
x_low = -78.22; % longitude low
x_up = -77.30;  % longitude up 
y_low =  33.82; % latitude low 
y_up =  34.33;  % latitude up
[xp, yp] = meshgrid(x_low:dx:x_up, y_low:dy:y_up);

zp = interp2(xv, yv, z, xp, yp); % makes the zp array for depth 

% export xp, yp, and zp into text file to be imported into MIKE mesh generator!

% for loop to get needed data for xp, yp, and zp 


[m,n] = size(xp);  
xyz = zeros (m*n,3) ;
count = 0;

for i = 1:m 
   
    for j = 1:n 
       count = count+1;
       
        xyz (count, 1 ) = xp (i,j);
        xyz (count, 2 ) = yp (i,j);
        xyz (count, 3 ) = zp (i,j);
        
    end
end


xyz = xyz(1:count,:);
save mesgrid.xyz xyz -ascii

This code just takes all the data and put them in coloums and able to save it as an .xyz file.

[Image Analyst]

Make it easy for us to help you. Please attach 'crm_vol2.nc'.

[Nicholas Deosaran]

I would love to attached the 'crm_vol2.nc' file but it is to big to attached even when its zipped and compressed.

https://www.ncei.noaa.gov/metadata/geoportal/rest/metadata/item/gov.noaa.ngdc.mgg.dem:305/html

is the link i got the infomration from and "download NetCDF File"

Answer 1

[Jan]

I do not see, where your filter out elevations greator 0.

It is faster to call interp2 with vectors as coordinates. So avoid calling meshgrid but provide the vectors directly.

Replace:

[m,n] = size(xp);  
xyz = zeros (m*n,3) ;
count = 0;
for i = 1:m
    for j = 1:n 
       count = count+1;
        xyz (count, 1 ) = xp (i,j);
        xyz (count, 2 ) = yp (i,j);
        xyz (count, 3 ) = zp (i,j);     
    end
end

by

xyz = [xp(:), yp(:), zp(:)];

[Nicholas Deosaran]

The question I have is how do I filter out anything over and elveation of 0 in the zp variabile.

like I want to get all the information in the x y and z. But only the infometion where zp is below 0

[Walter Roberson]

xyz = [xp(:), yp(:), zp(:)];
xyz(xyz(:,3) > 0, :) = [];

[Nicholas Deosaran]

Thank you!