Help with repairing LAS File

[Jonathan Dandois]

Does anyone have any good resources or suggestions for trying to repair a LAS file? The command lasinfo returns 'error: invalid file signature' and lasinfo -repair returns 'ERROR: wrong file signature '8'.

Thanks, 

Jonathan

[Nick Vaughn]

If even the file signature is incorrect, I doubt that this is really a LAS file. If you open in notepad or another text editor, what do the first few lines look like?  The first four characters of the first line should be 'LASF', followed by a bunch of strange characters indicating this is a binary file.

-Nick

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[Jonathan Dandois]

Thanks Nick, 

The first character just says '8'.  I have other LAS files from another project that I know work just fine.  When those are loaded into notepad the first characters are 'LASF'.

I have attached one of the LAS files that is giving me trouble.  

Thanks, 

Jonathan

--

Jonathan

[Kirk Waters - NOAA Federal]

There are no intelligible ASCII strings in that file that might give clues to what it really is. Do you know where/who it came from?

Kirk

[Jonathan Dandois]

That is my plan now, try to head back to the source.  In searching around the webs, including within this group, I had seen mention of LAS header repair options and wanted to get some opinions on that first as the data are over 5 years old now.  But it seems like there might be some larger issue than just the header.  

Thanks!

Jonathan

[Terje Mathisen]

Jonathan Dandois wrote:
> Thanks Nick,
>
> The first character just says '8'. I have other LAS files from
> another project that I know work just fine. When those are loaded
> into notepad the first characters are 'LASF'.
>
> I have attached one of the LAS files that is giving me trouble.

I've looked at that file, it does in fact look like it could be a
partially scrambled LAS file, with point record size = 20 bytes:

There are some very obvious patterns in a hex view with a period of
exactly 20 bytes, I would like to make a little experiment, copying a
valid header from another file on top of the broken file and see what
happens.

If that doesn't work, then I'll try to add some padding bytes (1-19) and
see if any of those alignments result in valid/plausible point data.

Terje

- <Terje.M...@tmsw.no>
"almost all programming can be viewed as an exercise in caching"