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PostPosted: Mon Nov 23, 2015 2:52 pm 

Joined: Tue Mar 18, 2014 7:19 pm
Posts: 2
Hi all,

Can someone explain how to convert a GPR image (.jpeg) to a GPR data format?
Thank you very much.

Best regards,

PostPosted: Fri Nov 27, 2015 7:42 am 

Joined: Tue Nov 30, 2010 3:21 pm
Posts: 30
hi geopgarcia,
there does not seem to be an available IMG to GPR data converter available, although you could try some of the seismic oriented converters that do the IMG to SEGY conversion (simple google search returns quite a few responses)
the other approach would be to make the converter yourself that would do the something like this:
1. Convert JPG to 8 or 16 bit BMP - I believe JPG is a compressed lossy format , so it would maybe be better to use uncompressed format to avoid potential artifacts
2. Read the number of pixels in horizontal and vertical direction - horizontal value will be your number of traces and vertical will be your number of samples per trace
3. Strip everything from the BMP except the pixel array - you may want to check the color table information before striping, maybe there is a way to use it to advantage
4. Convert each color to its 8 or 16 bit integer value and create new array - the color is going to be represented as a hex value triplet (#BBGGRR) if I am not mistaken, but you need a single "amplitude" number value in the GPR data, this is the hard part, but maybe you can figure out how to use the color table information to make it simpler, I believe that the Black---->White grayscale image palette would be easiest to deal with
5. From the image calculate the trace separation as length from the horizontal scale/number of traces from step 2 - this will be the trace/m or trace/s value
6. Write down the value for Time(ns) from the vertical scale shown in the image and maybe calculate the time interval between the samples as Time/number of samples from step 2 - some GPR file formats use Time value,some use time interval value in the header
7. Select the GPR file format you will use to save your data into (SEGY or one of the better documented proprietary formats - RD3 or DZT sounds like a choice) and make the header of those files based on the information gathered in the previous steps - which values from above depends on the selected file format
8. Fill up the rest of the header as needed - depending on the selected file format for the output there may be some other values you need to fill up, like RDP and such
9. Append your created data array after the header - the data array may need some manipulating depending on the selected file format
10.Open the newly created file in a GPR postprocessing software
(11.) Share your converter tool with us here at GPR-forum :D
Depending on the size and quality of the starting image you may need to downsize or upsize the image before starting, to give you a reasonable amount of points in the horizontal and vertical direction - I suggest that you do that part with any image processing software before going to the other steps.

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