Convert large xyz file into grid

Question

Yoni Verhaegen -WE-1718- 2019-10-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/486648-convert-large-xyz-file-into-grid

评论： Sara 2020-12-7

I have a large XYZ file (300276x3, this file includes x and y coordinates (not lat/lon, but polar stereographic) and elevation z) and I'm wondering if it would be possible to convert this into a gridded dataset (n x m matrix). The xyz file can be downloaded from:

https://wetransfer.com/downloads/4ae4ce51072dceef93486314d161509920191021213532/48e4ee68c17269bd6f7a72c1384b3c9a20191021213532/60b04d

and imported in matlab by:

AIS_SEC = importdata('AIS_SEC.xyz');

I tried:

X= XYZ(:,1);
Y= XYZ(:,2);
Z= XYZ(:,3);
xr = sort(unique(X));
yr = sort(unique(Y));
gRho = zeros(length(yr),length(xr));
gRho = griddata(X,Y,Z,xr,yr')
imagesc(gRho)
Requested 300276x300276 (671.8GB) array exceeds maximum array size preference. Creation of arrays
greater than this limit may take a long time and cause MATLAB to become unresponsive. See array size
limit or preference panel for more information.

I tried:

% Get coordinate vectors
x = unique(XYZ(:,1)) ;
y = unique(XYZ(:,2)) ;
% dimensions of the data
nx = length(x) ; 
ny = length(y) ;
% Frame matrix of grid 
D = reshape(XYZ(:,3),[ny,nx]) ;
% flip  matrix to adjust for plot
H = flipud(H) ;
% Transpose the matrix 
H = H' ;  % Check if is required
surf(x,y,H) ;
Error using reshape
To RESHAPE the number of elements must not change.

I can now plot the nx3 file with scatter3 (see image)

scatter3(XYZ(:,1),XYZ(:,2),XYZ(:,3),2,XYZ(:,3)) ;
colorbar

But I'd like to do it with imagesc. Hence, I would like to convert the nx3 file into a nxm matrix (in raster/gridded format) and as en extra I would like it as a geotiff file for use in QGIS.

Thanks!

3 个评论
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Chad Greene 2020-9-26

Have you seen my xyz2grid function? I think it'll do what you want.

Sara 2020-12-7

Hi, where is the function? i did not see it in the MATLAB helo. I also I did net know where I can the download

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Answer 1

Chad Greene 2020-9-26

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/486648-convert-large-xyz-file-into-grid#answer_500704

Try my xyz2grid function. It's fast, easy to use, and one of the examples in that documentation link shows how to grid up an Antarctic dataset just like yours.