The Nanoscale World

.flt file format

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lgc posted on Tue, Jul 10 2012 3:34 PM

I wonder if anyone can help me with explaining the [Data] field in .flt files. Or else, point me to the right resource.

Thank you very much.

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Answered (Verified) replied on Thu, Jul 12 2012 5:07 PM

Hi lgc,

I think you are maybe not reading the data description correctly. We do not store xyz data but rather z data (or any other quantity an AFM can measure). The xy locations can be recreated from the information in the header file, i.e. scan range, # of data points.   Maybe this short example helps shedding light onto the subject:

 

The actual data is float binary raw data. The data is a 2D array looks like data[.. , ..].

For example:

 

[Data Parameters]

DataOffset=  865

ResolutionX=128

ResolutionY=128

 

[Data}

This is the actual array like data[128, 128].

 

In the C you would be reading the array ‘data[128, 128]’ directly from the file (opened in binary mode) starting from file pointer =865 bytes.

 

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Answered (Not Verified) replied on Thu, Jul 12 2012 11:35 AM

Hi lgc,

I am really not sure what you mean by that question. I did post the description of the data format earlier. The header states the descritption of the data that follow. Each data point is the represented as a floating point value. Now, representing data points as floats might be unusual as they were historically just 16bit integer values. We went to floats as this allowed us to cover more dynamic range.

I hope that helps,

Stefan

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lgc replied on Thu, Jul 12 2012 3:27 PM

Stefan,

Thank you for your input. As I mentioned earlier, in the file explaining the format you attached there is an explanation to almost everything in the header. However, there is no explanation (except for "...") for the bulk of data; that is, beyond [Data]:

I am looking for something like 'float, float, float,"\n"' (in C jargon) corresponding to x,y,z and the newline character, respectively, for example. Or 'int, double, double, double", or anything along these lines.

What I need is to process these values in order to calculate fractality and roughness, among other things.

I'm all ears.

Regards.

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Answered (Verified) replied on Thu, Jul 12 2012 5:07 PM

Hi lgc,

I think you are maybe not reading the data description correctly. We do not store xyz data but rather z data (or any other quantity an AFM can measure). The xy locations can be recreated from the information in the header file, i.e. scan range, # of data points.   Maybe this short example helps shedding light onto the subject:

 

The actual data is float binary raw data. The data is a 2D array looks like data[.. , ..].

For example:

 

[Data Parameters]

DataOffset=  865

ResolutionX=128

ResolutionY=128

 

[Data}

This is the actual array like data[128, 128].

 

In the C you would be reading the array ‘data[128, 128]’ directly from the file (opened in binary mode) starting from file pointer =865 bytes.

 

  • | Post Points: 13
Top 50 Contributor
23 Posts
Points 275
lgc replied on Thu, Jul 12 2012 5:45 PM

There you are!

Much better so!

 

Thanks a lot .Big Smile .

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replied on Thu, Jul 12 2012 5:57 PM

No problem. Good luck with the programming.

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