Unable to get RTK Fix on Postcard

GPS/GNSS Development Boards
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Hello, I received the Postcard last week and that’s about as long as my endeavor into GNSS/RTK has been. Complete Newbie. I have been reading up on the technology but my understanding is far from proficient and it’s been a steep learning curve.

I have updated the RTK Everywhere Firmware (version d2.2), as well as the LG290P Firmware (LG290P03AANR01A04S_BETA0212). I get the accuracy units to display on SW Maps.

I am using an iPhone with SW Maps to connect to the Postcard and utilize the NTRIP client. Once it’s all connected I can achieve RTK Float and it remains in this state. What I notice is the delta H jumps back and forth between values every half a second. For example it will say .465/.920/.465/.920/.520/.960 and on and on every half second. It does not matter how long I let it sit.

I am using the Earthscope NTRIP caster, the port: 2101 (RTCM 3.1), 2105 (BINEX), and 2110 (Processed PPP, currently unavailable). All positions are in ITRF2008.

I have it set to port 2101 in SW Maps, using NTRIP Version V1 and “Send NMEA GGA to Caster” set to on.

The Mount Point I am connected to is between 1 km to 20 km depending on where I am when trying to get the fix. SW Maps typically shows around 30 satellites fixed at any one time. Wide open sky and I have tried it in multiple locations.

I would like some advice on how to obtain an RTK Fix. I have a feeling it is the settings on the Postcard and the way it is trying to interpret the data from the NTRIP client but I cannot recognize any setting that would be helpful.

I did see there is a place to put caster details on the Postcard under the GNSS Receiver menu. It is set to the Mtpoint at Sparkfun in Colorado using rtk2go. When does this come into play? If it is set to enable, does it default to this client?

Full disclosure, I did manage to get RTK Fix for about 5 seconds earlier today but then it went right back into Float.

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You can leave that Disabled since you are using SW Maps with it’s NTRIP Client.

You did a great job explaining the details, but you didn’t mention 2 things that come to mind:
Does the Rover have a clear view of the sky ? [Edit] sorry you did mention that :slight_smile:
What Antenna are you using ?

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Was the 5-minute fix only when you were close to a mountpoint, or were you far away then?

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For the antenna, I am using the stubby multiband helical sold by Sparkfun.

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It was a 5 second RTK Fix and I was approximately 20 km from the mountpoint.

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Ah, gotcha. If you have another multiband antenna around can you try swapping it out for the helical one to help eliminate it as a suspect?

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20km is pretty far. I have had good luck with the multiband antenna on a survey pole.

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I tried another antenna, EOS antenna ANT-L1L2L5, with the same results. I was a little over 6 kilometers from the mtpoint. After that I tried the same mtpoint but using a different caster and I was able to get a fix, so I am confident the postcard can do it. Both antennas were receiving from over 30 satellites. If that’s the case, would switching antennas really make a difference?

Once I got the fix I realized the dot turns green to signify it. When I had mentioned I got a fix in my previous post I had a blue dot, which actually means its a standard gps point. So disregard that item of information.

I will keep playing around with the postcard. Let me know if you have any thoughts or other ideas I should try.

Thanks for your help

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Was that with the 5" (12cm) base plate? That’s typically the minimum size to shoot for

Ideally you’d be within 10km of the Mount Points so the signal paths at your location are sufficiently similar. As they get more sparse, having a VRS use three to get a more localized estimate might help

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yes, the antenna had the base plate attached. Thank you for the explanation of why the the distance from the mtpoint is important. I kept wondering if the mtpoint data is being relayed through the phone and not over radio waves then why would it make that much difference. But it clicked when you talked about the signal paths.

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I can’t get RTK fix (only float) with the postcard and swift NTRIP service, only RTK float.
I’ve got the same setup with the helical antenna using SW maps.
I can connect no problem but I’m not geting a “FIX”
BTW after checking the “RTK Float” was no better than what I get from my phone anyways.

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I can tell a real antenna will solve your problem most likely but I have also had times where float was inevitable due to area. GPS isn’t complete magic in certain situations.

The way RTK works is there needs to be common satellites for both the correction or base and the rover for it solve the equation.

I would wager the helical antenna just doesn’t pick up enough stuff. Not even sure if picks up all the constellations?

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They say im 45km away from base station here in Yucca, AZ.
I knew I should have bought the better antenna. Maybe i have to build a base station but its gonna be $$

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I managed to get RTK fix using skylark after all, it works pretty good but it takes a while to get the fix. I ordered the better antenna, maybe we’ll setup a base station, there aren’t any around my area, they say you can make money with them?

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You were able to get a fix from 45km away? that’s pretty good. I’ve had good luck with the helical antenna 10km or closer to the mtpoint.

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It sounds like they’re using PPS instead

As for money-making, we did partner the x5 with onocoy, although we don’t really have any guidance for such :-/

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I’m 1500’ above the Base LOS in the desert, VHF/UHF should work.

It takes a while to get a fix in some spots tho, the UFO antenna on a post should improve things.