CODEWITHSUNDEEP
matlabgridinterpolationrastergeometry-surface
MBL
MBL

Reputation: 1227

MATLAB XYZ to Grid

I have a tab separated XYZ file which contains 3 columns, e.g.

   586231.8       2525785.4           15.11
   586215.1       2525785.8            14.6
   586164.7         2525941           14.58
   586199.4       2525857.8           15.22
   586219.8         2525731            14.6
   586242.2       2525829.2           14.41

Columns 1 and 2 are the X and Y coordinates (in UTM meters) and column 3 is the associated Z value at the point X,Y; e.g. the elevation (z) at a point is given as z(x,y)

I can read in this file using dlmread() to get 3 variables in the workspace, e.g. X = 41322x1 double, but I would like to create a surface of size (m x n) using these variables. How would I go about this?

Following from the comments below, I tried using TriScatteredInterp (see commands below). I keep getting the result shown below (it appears to be getting some of my surface though): enter image description here

Any ideas what is going on to cause this result? I think the problem lies with themeshgrid command, though I'm not sure where (or why). I am currently putting in the following set of commands to calculate the above figure (my X and Y columns are in meters, and I know my grid size is 8m, hence ti/tj going up in 8s):

F = TriScatteredInterp(x,y,z,'nearest');
ti = ((min(x)):8:(max(x)));
tj = ((min(y)):8:(max(y)));
[qx,qy] = meshgrid(ti,tj);
qz = F(qx,qy);
imagesc(qz) %produces the above figure^

Upvotes: 2

Views: 10500

Answers (3)

alex
alex

Reputation: 11

Griddata and tirscattteredinterp are extremely slow. Use the utm2deg function on the file exchange and from there a combination of both vec2mtx to make a regular grid and then imbedm to fit the data to the grid. I.E.

for i = 1:length(X)
[Lat,Lon ] = utm2deg(Easting ,Northing ,Zone);
end 

[Grid, R] = vec2mtx(Lat, Lon, gridsize);
Grid= imbedm(Lat, Lon,z, Grid, R);

Upvotes: 1

Oli
Oli

Reputation: 16035

Maybe you are looking for the function "ndgrid(x,y)" or "meshgrid(x,y)"

Upvotes: 0

Nzbuu
Nzbuu

Reputation: 5251

I think you want the griddata function. See Interpolating Scattered Data in MATLAB help.

Upvotes: 3

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