Just noticed that the "GPS of choice" for the Pixhawk 2 now appears to be "Here", and that there's an RTK version.  Is there any doco on these?  In particular the RTK?

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They are U-blox receivers,  and HERE is made by Hex Aero and ProficNC (the makers of Pixhawk).  I think they are just reference designs of Ublox with the Pixhawk I2C connector type..  They are known to be some of the best receivers in their form factor. 

I would not buy into RTK when you can just implement PPP yourself on the normal receiver and get nearly the same level of accuracy.

What is PPP?

Precise Point Positioning, don't think it's as accurate (not far off though) but should be cheaper (I think)

Juan Carlos Hdez said:

What is PPP?

And this drives us again to the first post, more "doco" is needed on this topic!

PPP?  New one on me.  Is this not to be confused with PPK?  RTK and PPK (Real Time Kinematics and Post Processed Kinematics) GNSS are the ways to do that. For this application, PPK is often superior because real time position is not required, and PPK requires no radio link so it is more reliable and works over greater distances than RTK. In addition, more processing power can be applied to the PPK position solutions since the processing is done back at the office on your computer and not on a smaller GNSS receiver.

https://info.photomodeler.com/blog/survey-grade-accuracy-with-a-dro...


I just looked at your site PhotoModeler UAS- Martin L, very interesting but I am finding it very confusing lately.  I have been building UAS for a few years now and I remember when I would know of all the best features and sensors available (or at least the main ones).  Lately I have been seeing how many options are around and I am lost.  Between RTK, PPK, GNSS, the different ground station and air GPS systems used to acquire accurate positioning, oh my head is spinning.  Seriously though, I have just had to upgrade one of my aerial platforms and I'm using a Pix 2.1 with the hope that the edison carrier board might come in handy for setting up a accurate positioning system for mapping.  I was looking at the vu8 Lidar from Leddar I think there was a version for around $500 and was hoping to use Lidar as a way to produce accurate data.  Does anyone know which the best solution for the Pix 2 in regards to this?  I also wanted to set up a dual GPS on the aerial platform (pixhawk 2)  is there any documentation about doing that?  All I can find on dual GPS was on the px4 site and it talks about connection of a gps on the ground station laptop, I think this is something like the RTK system.  I need to do more reading but any help would be great.  I have the plan of having a Sony A6000 on the pix2 UAS I am also setting up a T960mm frame with 17" props but running a DJI A2 on that to give myself options to use both DJI and Pixhawk in case I want to use sensors specific to the brands.  

I do agree with -Andresiko, there is a lack of documentation and video's on the Pixhawk 2.1.  I was hoping to help the situation by uploading a build video of the Px2.1  Any help about the right sensor solutions and software choices would be good.  I still use Mission Planner but I hear QGround Control is a good solution, and if it has significant benefits I will change but I like to stay with familiar systems.  

Martin Lachance said:

PPP?  New one on me.  Is this not to be confused with PPK?  RTK and PPK (Real Time Kinematics and Post Processed Kinematics) GNSS are the ways to do that. For this application, PPK is often superior because real time position is not required, and PPK requires no radio link so it is more reliable and works over greater distances than RTK. In addition, more processing power can be applied to the PPK position solutions since the processing is done back at the office on your computer and not on a smaller GNSS receiver.

https://info.photomodeler.com/blog/survey-grade-accuracy-with-a-dro...

Precise Point Positioning (PPP) is a zero-difference technique (i.e. no reference receiver needed) as opposed to RTK, where you need a reference receiver to cancel common errors. in PPP you use precise information of GNSS orbits and clocks and an accurate modelling of the GNSS signal in order to obtain positions at the level of centimeter accuracy.

Note that, in RTK, in order to obtain an accurate position estimate for the rover receiver, you need an accurate estimate of the reference receiver position. You actually use PPP to obtain such accurate position. Also, in order to properly use PPP, you need multi-frequency GNSS receivers. While you can still use single-frequency GNSS receiver with RTK, you cannot achieve the same level of accuracy with those receivers using PPP.

Hope this helps!

Miquel

http://www.rokubun.cat

Hello Miquel,

When your system will be available to test? We are developing a custom designed UAS for oil&gas and survey applications.

Thanks.


Miquel Garcia said:

Precise Point Positioning (PPP) is a zero-difference technique (i.e. no reference receiver needed) as opposed to RTK, where you need a reference receiver to cancel common errors. in PPP you use precise information of GNSS orbits and clocks and an accurate modelling of the GNSS signal in order to obtain positions at the level of centimeter accuracy.

Note that, in RTK, in order to obtain an accurate position estimate for the rover receiver, you need an accurate estimate of the reference receiver position. You actually use PPP to obtain such accurate position. Also, in order to properly use PPP, you need multi-frequency GNSS receivers. While you can still use single-frequency GNSS receiver with RTK, you cannot achieve the same level of accuracy with those receivers using PPP.

Hope this helps!

Miquel

http://www.rokubun.cat

Hi!

Our Argonaut GNSS Receiver is now in prototype stage (we are making the test and benchmarking) and the production will start soon (before ending of June). We expect to have the first units in 2 months time approximately.

Do not hesitate to contact us if you need more information

Best

Miquel



ActionDrone said:

Hello Miquel,

When your system will be available to test? We are developing a custom designed UAS for oil&gas and survey applications.

Thanks.


Miquel Garcia said:

Precise Point Positioning (PPP) is a zero-difference technique (i.e. no reference receiver needed) as opposed to RTK, where you need a reference receiver to cancel common errors. in PPP you use precise information of GNSS orbits and clocks and an accurate modelling of the GNSS signal in order to obtain positions at the level of centimeter accuracy.

Note that, in RTK, in order to obtain an accurate position estimate for the rover receiver, you need an accurate estimate of the reference receiver position. You actually use PPP to obtain such accurate position. Also, in order to properly use PPP, you need multi-frequency GNSS receivers. While you can still use single-frequency GNSS receiver with RTK, you cannot achieve the same level of accuracy with those receivers using PPP.

Hope this helps!

Miquel

http://www.rokubun.cat

Yes, I'm interested to know more.

Please let me know where I can contact you directly.

Thanks.

Of course! Please drop us a mail at info@rokubun.cat (please include your contact details as well)!

Best

Miquel

ActionDrone said:

Yes, I'm interested to know more.

Please let me know where I can contact you directly.

Thanks.

Dual GPS systems on drones has been around for a long time.  In fact, I don't make birds without dual GPS systems.  One plugs into the pixhawk 2.1 itself (GPS1) and the second one plugs into the GPS 2 slot.

BUT

There is a caveot!  The GPS1 slot on the Pixhawk 2.1 is the I2C bus, like the one Pixhawk 1 has.  Pixhawk 2.1 has an external I2C-2 bus, separate from the I2C bus.  Currently some sensors (lidar) does NOT work on the I2C-2 external bus. 

Point being, you can do dual GPS units with the Pixhawk 2.1 but you might have problems running anything else. 

A problem with running 2 GPS is that when the autopilot swaps to the better Hdop GPS unit (better values) your drone will MOVE to a different position (we call it hunting, as in hunting for the right spot to be in) and it can do it 5 feet from the ground.  Dangerous as hell, but a rare occurance.

As of 3.4 blended GPS is up and running, so if you wanna do dual GPS I'd read up on that logic.

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