ASCII header - how do you create?

ElanorGowland — Thu, 24 Oct 2013 11:14:15 GMT

I have some very large xyz files (ASCII) which are space separated. I wish to put these into rasters to view with other data I have. My ASCII files do not have headers (which I believe I may need, so please can someone tell me how to generate them from the file).

For my smaller files I got round this using the following process, but now my files are too large (>5GB) to do this.
Copy file (and change name as per table below).
Change format to .asc
Find and replace space with comma.
Ensure schema.ini has file as CSV and no header fields (if file doesn�??t exist then add)
ArcCatalog: Create feature class from XY table
Choose World, WGS_1984 as coordinate system
Feature to Raster (from Toolbox)

Please can someone help, I am fairly new to Arc, so am unaware of all the options - perhaps there is something in Python that can help. I have seen the scripts available http://arcscripts.esri.com/details.asp?dbid=14268 but am unaware how I can use these without the headers in my ASCII files, and also once I have the data in shape file format I still have the problem of trying to convert into raster - as I have tried (using the above method) and my computer ran for 2 days and lost connection with it's licence.

Thanks,
Elanor.

Re: ASCII header - how do you create?

XanderBakker — Mon, 04 Nov 2013 11:35:36 GMT

Hi Elanor,

For this size of data it's better to use LAS files. In order to be able to use LAS files in ArcGIS your text files should be translated to LAS. This can be done using the LAStools tool called "txt2las.exe". Many parts of LAStools are now available under LGPL license.

The command that translates your input text file to a output las file would be:
txt2las -i input.txt -parse xyz skip 1 -o output.las -set_version 1.2

The skip 1 refers to skipping the first line for being a header. If your text file doesn't have a header just omit the "skip 1" in the command. (txt2las readme file)

After creating the LAS file(s), you can "Create a LAS dataset (Data Management)". Once you have a LAS dataset you can use "LAS Dataset To Raster (Conversion)" to convert your XYZ points to raster.

Some more reading:
Creating raster DEMs and DSMs from large lidar point collections

More on LAStools:
http://rapidlasso.com/

Kind regards,

Xander

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ASCII header - how do you create?

Re: ASCII header - how do you create?