Here+ does not "hold" RTK Fixed status reliably - Help please!

#7

http://ardupilot.org/copter/docs/common-here-plus-gps.html

#8

@hdtechk I have read the linked document multiple times.
As far as I can see, it does not contain a suitable u-blox config that can be uploaded to the base, nor does it take into account the use of NTRIP corrections to the base and an absolute position setup for the base as I outlined above

In yet another test earlier today, I actually obtained a rtx Fix within U-center (after a long time, like an hour or more, with NTRIP corrections applied). On disconnecting from u-center and connecting to Mission Planner, the status dropped to Float. (I don’t know if this status displayed in the HUD applies to the base? or the rover/ both?)
The Here+ rover is mounted on a thin plastic canopy, which has copper shielding inside, which to my understanding should act as a ground plane then.

So the issue remains: I cannot reach a reliable, steady rtk fix status…

#9

We have had pretty much the same experience as you with the here + using ntrip.

We’ve given up burning any more time trying to get it to work and bought a drotek f9p module and now get a fix all day long in seconds.

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#10

Thanks for pitching in. Seeing the reports, I was afraid of that - needing to spend more money and having a 600$ item - advertised to achieve cm accuracy - laying around useless, therefore my efforts.

Maybe Hex will consider a discounted upgrade/ trade-in program for Here+ customers once the HerePro is out?

#11

It is not a problem with Here+ in particular, i have had here+ and reach from emlid. Both struggle to get and keep a fix on a stand alone test rig, let alone a flying drone, M8 is very limited due to its single frequency support.
F9P is the only way to go, double frequency is a must if you want to have reliable and quick rtk fix. I am impatiently waiting for the new Here Pro and will get it on day one if it is uavcan. The perfect solution wold be to have a 3100 compass on it too but i doubt it will.

#12

I do not think we have a $600 useless items. L1 does work and I get 2 cm results daily using static post-processing. To get a fix you need 12 minutes plus 2 minutes per KM for your base line. If you are using NTRIP your baselines will be very long. If you set up a base you will have shorter baselines and better results. There is something off with the M8P settings and I think we need a good set of starting parameters from ublox. For one the default elevation mask is way too low at 5deg. SV’s at that low elevation will only confuse a receiver, it is much better to maintain a lock on 8sv’s than to intermittently get 15-20 sv’s. You will get bad fixes using low sv’s and the only way to catch the error is to repeat the survey which we can’t precisely do in the air.
The wife said NO to the L2 upgrade so for now I am committed to getting the M8P to work. It will especially on a drone flying above most obstructions. I will share any parameters I find that work & lets not call it a paper weight yet.
Start by setting the elevation cut off at 10-15 deg.
If anyone on this site needs a good base position I would processes it for you. I would need your Rinex files .19o & .19n

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#13

Same here… made the mistake of buying 3 of the Here+ units!
After days of frustration not getting more than a few seconds worth of steady RTK fix in a clear open field we finally gave it up. In the end settled for the Septentrio which was not cheap but the RTK fix is rock steady! Due to the nature of the project we could afford it but I really feel bad for the guys that spend their hard earned cash of these units, which I consider very optimistically being sold as RTK units…
Anyway @camti if you ever find the solution I would be all ears since we still have 3 of them laying around…

#14

Accuracy around a waypoint is not only defined by the gps itself.

#15

Keen to get better parameters for uBlox if possible, let’s see if we can identify any areas for improvement and get them into the next firmware

#16

@philip
I‘d gladly be enlightened what else contributes to accuracy around the waypoint!

I have reigned in the param WPNAV_RADIUS to 10 cm and give it a couple of seconds at the waypoint to settle in position.
What are other things to improve real time (not PPK) accuracy?

#17

We had similar issues with the Here+ initially.
Two big things to remember if you want a reliable fix:

  1. Ground plane both ends.
  2. The fix state in mission planner is very dependent on the health of the EKF (in particular the heath of the compass in our case). If everything else is not in tip top shape getting an RTK fix is difficult to achieve reliably.

Our application was a very large rover (150kg’s) and it had to steer within 5cm to remain within a set of plant rows. once we sorted out our compass we were all good.

Another thing that we found useful was to log the Here+ base then ppk process the location and punch that into mission planner. It saves a lot of time surveying in and gives you the best absolute accuracy.

Dont despair the unit is completely capable of what you are looking for t just needs a healthy environment.

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#18

Have a look at Mathew’s post above.

#19

I ran 3 test with good results using 10 and 15 degree sv mask
60% - 80% open sky with 20% horizon view, 50 year old trees on my lot and all adjacent 0.2 acres lots, not an open field.

10 degree mask took 5 minutes to fix. then float - fix for 2 minuted until a solid fix for 7 minutes. after that I lost the fix and position was only about 1 -2 feet accurate for the next 20 minutes.
this 1st test held 16 -17 sv’s

15 deg mask took 4 minutes to first fix then float fix for 5 minutes at an accuracy of about 0.5 feet, at 10 minutes it fixed and held a solid fix for 45 minutes.
I also set the s&r mask to 30
this 2nd test had 15 -16 sv’s

test 3 same as test 2 I got a 2 minute fix, it stayed fixed

Yes! the Here+ works just like a survey grade L1 receiver should work.
ucenter1

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#20

Have been using the here + for a while now. and use it with NTRIP
Like all L1 rtk gps recivers it will take up to 10 min to get a fix, if to turn it on it side it will lose fix.
You get a fix more easily when in the air. so maybe take off and loiter.
I limit my bank angle to 30 deg so as not to lose lock in the turns.

If it does drops to float while on mission I don’t worry to much, it seem pretty close to what FIXED is anyway.

And I never do a survey with out at lease 5 GCPs on the ground, and only rely on RTK when you really can’t get on the ground.

All in all its a good unit. and can’t wait for the l1 l2 here pro

#21

@Corrado_Steri I understand that many people are impressed with the F9P, and that multiband receivers have many benefits. At the same time I have spent considerable money on the Here+ M8P already, therefore have an interest in getting it working as advertised, and am trying to sort through the various reports of people encountering the same problems I have (and have given up), and meshing them with others who are saying it is usable…

#22

@Mathew_Herbert thanks for pitching in.

As mentioned above, the base has a groundplane, and the rover is mounted on a thin plastic canopy, which has copper shielding inside, which to my understanding should act as a ground plane then.
Additionally, I have not noticed EKF issues - I am plenty “green” there, with low values, a good compass calibration as well as good Compass Motor Calibration.

Also, as outlined, I am acquiring the precise location (using NTRIP), and then am using this static position in MP.

#23

Trouble is, as mentioned above, for my application I cannot operate with post-processing.
Additionally, I need to fly low to the ground.
How have you configured your base and rover? Would you be willing to share the config files for your Here+ modules (exported from u-center)?

When using a L1/L2 base stations from Septentrio, I can get a fix in well under 20 secs. My NTRIP provider (geared towards state surveying) has a high density of stations and notes that with the augmentation of VRS the baselines in effect are very minimal and able to achieve very high accuracy throughout the territory covered.
I do see a reference in their docs to making use of NMEA 0183 GGA/ bidirectional communication, if that info is of any help.

Gladly. Except that this is likely something the manufacturer will need to work out directly with u-blox, as I can’t see getting a direct response from them for a firmware update.

#24

@mtnsurveyor thanks for running these tests and sharing the result.

I will try to reproduce this in u-center - but am reliant on @philip to have this implemented in the firmware, so that it can be used in the Mission Planner/ Ardupilot universe.

What is the “s&r mask”? Where do I find that? Do you mean the dbHz value in C/NO Threshold?

These settings also have to be changed on the rover, correct?

#25

@Leon_Dwyer thanks for pitching in.
For my accuracy needs, I seem to observe a considerable drop from fix to float in terms of a steady position. Plus being higher in the air is not a viable option for my application, nor are GCPs, as I cannot use PPK.

#26

I mentioned the post processing because it is the same in terms of getting accurate results. The 12 minutes + 2 minutes per KM is a formula from Ashtec tech support many years ago. It applies to L1 kinematic fixes only. L1 & L2 GNSS will fix in under 10 seconds and almost works everywhere it is great stuff now.
Your rover wont work with any SV’s that your base does not have. If your base has 10 but your rover has 15 It can only use 10. In short you want you base getting everything. More open and a slightly lower cutoff is better.
I am still messing with the best elevation mask for these L1 units. 15 deg is a bit high however the float results are better than 5 or 10 deg mark and the fix is pretty solid. I think 13deg may be a better but I don’t know yet.
The Signal to Noise ratio has a cut off too. It is a bit confusing in Ucenter & I thought MP had a max value of 40 for SV use but you see the red line at 30 on the RTKinject. I do not know if changing these setting are helpful or the right thing to do. The Ucenter should have better default settings. Most of the parameter values are at 0 and I do not find help on the settings. I don’t know how Philip could implement something in Ucenter.?