Labview as wxtoimg for satellite signals

[cbutcher]

10 messages in and still nothing on the original topic! I wonder if that's a record...

maycarimarti10 - can you perhaps clarify what you want to do? I took a look at the software you mentioned (double-click to highlight, right click and 'Search Google For "..."' to everyone else 😉 ) and it seems like it's a piece of stand-alone software used to decode the data from an antenna and produce pictures.

@you wrote:

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@maycarimarti10 wrote:

I am new in Labview...I was doing reception of satellite signals with labview now I need take images as WXTOIMG software. Someone have any idea about this topic. Thank you!

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When you say you were 'doing ... in labview' and 'now I need to take images as WXTOIMG software' do you mean you previously have working LabVIEW code, and now you want to improve it so that your images output look like those produced by WXTOIMG, or (perhaps more likely) that you want to use the images produced by WXTOIMG in LabVIEW?

I don't see anything on their website about providing a useful input to other programs directly, so perhaps you could consider using WXTOIMG to produce images, and then import them to LabVIEW? What do you want to do with them?

[maycarimarti10]

My project is... the satellite captures signals and images, these images and signals are going to my antenna and usrp, they are seen from an interface in Labview. Now the signals are in my interface but I don't know as I can see the images in Labview.

[cbutcher]

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@maycarimarti10 wrote:

My project is... the satellite captures signals and images, these images and signals are going to my antenna and usrp, they are seen from an interface in Labview. Now the signals are in my interface but I don't know as I can see the images in Labview.

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"the signals are in my interface" - can you expand on this? You have the data from the antenna available in some form in LabVIEW and you want to produce an image from it? (As in, you want to reproduce the functionality of WXTOIMG?)

If so, I guess the places you need to be looking relate to the formatting of the data that you're receiving. I couldn't see anywhere to get source code for WXTOIMG, so I don't know that you'll get much help there, if what you're trying to do is replace it.

Maybe I've misunderstood?

[Muri777]

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@cbutcher wrote:

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@maycarimarti10 wrote:

My project is... the satellite captures signals and images, these images and signals are going to my antenna and usrp, they are seen from an interface in Labview. Now the signals are in my interface but I don't know as I can see the images in Labview.

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"the signals are in my interface" - can you expand on this? You have the data from the antenna available in some form in LabVIEW and you want to produce an image from it? (As in, you want to reproduce the functionality of WXTOIMG?)

If so, I guess the places you need to be looking relate to the formatting of the data that you're receiving. I couldn't see anywhere to get source code for WXTOIMG, so I don't know that you'll get much help there, if what you're trying to do is replace it.

Maybe I've misunderstood?

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I think they're saying that they've received the signals but cant change view them as an image? Maybe instead of raw data... I'm not sure

[maycarimarti10]

Yes, exactly... I want to do something similar to WxtoImg...I captured the signals, but the decoding of APT signals and the scanned images in LabView is more confusing. I was reading about other software, I think that everything is welcome!

[cbutcher]

I couldn't find a great deal of easily readable information on the file format, but it seems like a combination of wikipedia: Automatic Picture Transmission and this python repository should get you started.

If you upload some example data along with what the image should look like, more people might be able to try and work out how to get LabVIEW to process the data.

[rolfk]

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@cbutcher wrote:

When you say you were 'doing ... in labview' and 'now I need to take images as WXTOIMG software' do you mean you previously have working LabVIEW code, and now you want to improve it so that your images output look like those produced by WXTOIMG, or (perhaps more likely) that you want to use the images produced by WXTOIMG in LabVIEW?

It would seem to me that he has used one of these devices: http://www.ni.com/en-us/innovations/wireless/software-defined-radio.html to receive the raw satellite data and now wants to do something with this data, similar to what this wxtoimage software does. Since this software seems closed source and we haven't found a readily documented interface to feed in raw data and receive the image data from this software, it would seem that the decoding might have to be reprogrammed in LabVIEW.

The other option might be to connect the decoded analog output from the SDR to the sound card input and simply use wxtoimage or one of its concurrents anyways.

[cbutcher]

That was largely the conclusion I had drawn. I'm uncertain how easy it would be to reprogram the decoding in LabVIEW - probably easy if the user understands the encoding, and not so much if, like me, they don't...

[Atlas]

I know this is a stale thread at this point but it's less than a year stale and came up in a search for me...

So, those links on APT above would eventually get you where you need. As for the difficulty, it's not so bad- would make a great capstone to a 1st year DSP series. The short summary is this is a low data rate 8bit AM signal modulating a 2400Hz carrier which is in turn modulated onto a fairly narrow 60kHz wide FM carrier generally somewhere near 137Mhz. There are two channels of data- one is visual band and I think Near IR, the other is an offset visual for daytime satellites, or an IR band for evening satellites. Day/Night configuration is a function of how NOAA configures them, and you can receive day passes in the night, etc.  The channels are interleaved one raster line at a time into a single stream, there are two sync patterns, and then the next raster line is sent, this process repeating as long as you have a down link. So you'd grab the I&Q stream off of the radio, demod, and then read in as 8 bit unsigned ints. Or skip the I&Q and do the FM demod with a real radio and load the sampled wav file as the 2.4kHz modulated data. Though I haven't used LabVIEW for this in particular, I did once process the data within a linear algebra program and found it almost trivial to confirm those sync patterns manually as they are full signal to no signal alterations on a periodic basis. LabVIEW would be perfect for this type of thing given you'd eventually like visualization of the data. 

All this aside, the KLM users guide is what you really need. It details these satellites in all aspects and is a great learning resource, with a wealth of data spanning DSP to physics to satellite subsystems. APT is covered somewhere in section 4. HRPT is an L-Band vector modulated version that would make a nice advanced project after APT is tackled. Also, there are open source demodulators, some almost similar to G in a program called GnuRadio which sets up flow graph sketches looking like G (though are actually Python and/or C underlying them) 

KLM guide is currently at:

https://www1.ncdc.noaa.gov/pub/data/satellite/publications/podguides/N-15%20thru%20N-19/pdf/0.0%20NO...

[rolfk]

Great reply! I have to admit it's all still above the level that would make me say, yes I know how to write that in LabVIEW, partly because I never worked with DSPs nor did I do more than some basic AM and FM modulation examples in LabVIEW.

But given the links and the explanations I'm sure I could learn it if I needed to!