Facing Issue with using 2 GPS for Yaw

ArduPilot does all that automatically for you. What exactly do you want to change?

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Not only that, but NMEA doesn’t carry enough info to create RTCM3.

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Hi @Yuri_Rage and @amilcarlucas Thanks for your responses.

Yeah! currently I am using the RTK GPS system and it is working great. I just want to see the possibility of making this configuration work with non-RTK GPS, this is just for my understanding and learning.

I just want to take the raw data from the non-rtk gps and process it in my system/computer and send the generated RTCM3 data (after processing the raw data) to pixhawk as a correction for the other gps.

it seems like the .ubx format is the raw data format from the GPS. If I can get this kind of output format from the GPS, is it possible to make it work?

Could you please explain a bit more about what I might be missing here? I understand it might be a bit challenging, and not worth as the existing RTK GPS setup works well, but I’m curious and want to give it a try.
I apologize for bothering you with this again and again. Thanks!

If you’re using a non-RTK capable GPS, it’s unreasonable to expect that it will have the data required in its output stream be able to craft RTCM3 corrections. I assume this is all to try and save a buck, but the new dual antenna system from CUAV is so affordable that it’s hard to justify a kludge like you suggest, even if it were possible.

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It is simply not possible. The atmospheric corrections required for RTK operation are only available on RTK GNSS receivers.

It does not matter how much ammount of processing you do on .ubx raw data from a non-RTK receiver. You will never be able to create a proper RTCM datastrem to feed into a RTK receiver. And feeding it to a non-RTK receiver will not improve it in any way.

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I totally understand it, working on to find the data required to generate the RTCM3.

Actually, it is not like that. There are two reason for that, First is; for my understanding and learning and second is; to change the shape and size of this configuration. Nothing much.
I will give it a try and see if it works, do you know any library or software which can generate the RTCM3 data from the raw data? Thanks!

Here is a library to manipulate RTCM data https://rtklib.com/

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Totally agree, that’s my concern. That might impact big on the performance.

Yeah! you are right, I have to find a way to correct the other gps data based on the first gps RTCM data and then feed it to the pixhawk. In this case, there is a chance to make it work. Thanks!

I fear you’re wasting your time. GNSS hardware is a multi-billion dollar global industry. Don’t you think if it were possible to get cm level precision by processing data from a cheap receiver that someone would already be mass producing such a thing?


Hey @Yuri_Rage, You make a good point, and I want to clarify that I don’t need super-precise measurements down to the centimeter. If this setup can give me slightly better results than a regular GPS, that’s perfectly fine. My main focus is on improving how it calculates the Yaw direction, even though I understand it won’t be super precise in that regard. I’m comfortable with that limitation; I just want to test how well it can estimate Yaw.

Thank you for your input, and please don’t think I’m arguing with you (I can’t even think of that, you are like a teacher for me). Our back-and-forth discussion is incredibly helpful to me. I appreciate your advice, and I genuinely want to know your thoughts on using this setup for primarily Yaw estimation (just as a backup in areas with a lot of compass interference). Thanks :slight_smile:

You can not do GPS for yaw without RTK. Period.

You can also not improve non-RTK-GPS position with RTCM.

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I don’t perceive an argument, but rather naive enthusiasm. You say you don’t want cm level precision, but that’s exactly what you need if you aim to arrive at a yaw solution derived from antenna position.

ArduPilot can already achieve an imprecise yaw solution by calculating it from GPS course and filling in the gaps with gyro data. It works ok but tends to get a little funky during sharp or pivoted turns. Read up on GSF.

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Hey @Yuri_Rage, Totally understood. I guess now I don’t have anything to say and you are totally right, it will not work. I have tried to process the NMEA data and it showed errors (missing data) :slight_smile: so dropping this plan.

Thank you so much for all the explanation and making me understand how it works.

Btw, I found something else to work on, I want to use optical flow sensor for flying in Non-GPS regions. I know there are few options available but range of detection is less and people are suggesting to use external ultrasonic or lidar sensor for height estimation.

So I am thinking to make my own custom optical flow using pi camera and Maxbotic sensor.

I know this is not related to this topic, will create a new thread just thought to ask you first here. Thanks!