ascii2xyz

convert ARC ASCII text file to xyz

Description

ASCII2XYZ reads in a raster text file in ARC ASCII format and converts values to a m x 3 matrix of x, y, a z values.

This code is mostly vectorized and performs well with reasonably large files (see example below).

%read in a 25 MB file
a=dir('foo.txt')

a =

       name: 'foo.txt'
       date: '17-Oct-2008 08:53:34'
      bytes: 25437683
      isdir: 0
    datenum: 7.3370e+005

tic
xyz=ascii2xyz('foo.txt');
toc
Elapsed time is 8.110956 seconds.

Acknowledgements

The author wishes to acknowledge the following in the creation of this submission:
Raster to XYZ

• MATLAB release: MATLAB 7.6 (R2008a)
• Other requirements: Will likely only run on Matlab Version 7.1 (R14SP3) or later

[Joaquim Luis]

What if the ARC file uses xllcenter/yllcenter instead of xllcorner/yllcorner?

[Andrew Stevens]

Joaquim, Thanks for the comments. This file assumes that the coordinates are relative to the pixel center. I had no idea that "xllcorner" actually referred to absolute corner of the grid. I will post a modified file in the next few days that will account for the different coordinate reference systems.

[fran anwar]

sir....
I has an ascii file (.asc) but when l try to get the x,y and z, there is some error. it say " 'Error reading header information"..why sir?

[Andrew Stevens]

Fran,

This file is intended to read in an ASCII file produced by ARC GIS containing raster data. A properly formatted ARC ASCII file has header information which your file does not apparently have. Type 'help ascii2xyz' to see the required header format.

Andrew

[Ric]

Hey,
i'm trying to use this script, but it just outputs values of 0.051 instead of 51.(and about 10-17 numbers (depending on the coordinates) following) - it also would be just great to have an option of getting the script to output a .txt file, containing longitute, latitude, altitude (seperated by anything) - as my coal is to get ascii-data into a sql database. do you have any ideas?
as i'm not experienced in matlab in any way so it's not possible to improve the script myself though it's doing exactly what i need (exept for the output-prescision and output-file).
thank you very very much for writing the script in the first place, and even more for helping me!

best regards, ricardo