Identifying meteomodem m20 radiosondes & extract GNSS location #932
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The convertion for altitude looks fishy, can you elaborate about why it's 10 % not good ? |
I didn't understand the original data format/units coming from the packet and how it has to be converted. So I used sondehub.org to compare altitude with my results on the portapack and made an approximative conversion in the code. |
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You can find pre-release binary to flash your portapack/hackrf here to test it if you are not away from m20 launches or if you already collected some m20 : |
firmware/common/sonde_packet.cpp
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| @@ -109,6 +111,12 @@ GPS_data Packet::get_GPS_data() const | |||
| result.lat = reader_bi_m.read(14 * 8, 32) / ((1ULL << 32) / 360.0); | |||
| result.lon = reader_bi_m.read(18 * 8, 32) / ((1ULL << 32) / 360.0); | |||
| } | |||
| else if (type_ == Type::Meteomodem_M20) | |||
| { | |||
| result.alt = ((reader_bi_m.read(8 * 8, 32) / 100) - 48) / 250 ; //Conversion of altitude is actually a bit shifted, needs to be more accurate. | |||
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reading the linked decoder code, the translation would be:
result.alt = reader_bi_m.read(8 * 8, 24) / 10.
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What I changed from your code is that I only read 3 bytes as the alt is encoded on 3 bytes only (3 * 8 =24)
I dunno if it is compiling and I have no sonde to check.
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From what I've read further, just combining the 3 bytes and divide by 10 should do it
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@joyel24 have you read my review message? |
Yes I'm gonna work on it but I wanted to allow people to decode at least geolocation. It's more than enough for radiosondes hunters that want to collect them once on the ground. And I'm not sure I will be able to decode everything. I think it's better for everyone : Of course I want to make it work, more than that, I'd like to add other data like pressure or vertical/horizontal speed for example... |
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Okay let's do it your way :-) |
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Didn't expect changing the branch name will close PR... I'm gonna reopen this PR after working on altitude decoding or another data. |
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Harf you deleted the branch before I merge! |
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Okay |
#934 You can merge this one, I will use the current PR for further work. |
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Done for that. You can if you need to delete your source branch and sync your 'next' |
GNSS location is ok, no altitude yet.