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Re: ntrip and sending position

From: Greg Troxel
Subject: Re: ntrip and sending position
Date: Wed, 18 Dec 2019 17:32:38 -0500
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (berkeley-unix)

"Gary E. Miller" <address@hidden> writes:

>> I find that WAAS isn't as good as local DGPS from the USCG used to be,
>> even with a clear sky view.  But I have no hard data.
> Of course.  Local corrections are better than wide are corrections.
> But some GNSS receivers consider them equal when turning on DGPS
> status bit.

Agreed that they both count as DGPS.  I just meant that I suspect that
between local and rate that the local ones are better.

>> I am headed to corrections over the internet to get more accurate
>> real-time positions via navigation solutions, so I can map in the
>> field, and also later.  I would be very happy with 2m accuracy.
> Good luck with that.  My NEO-M8T getting RTCM2 corrections from
> a station 2 miles away gets maybe a CEP(50) of maybe 3 meters.  I guess
> I need to run a gpsprof on that.

Me too, on my data - but even 3 is better than what I get with WAAS
while hiking.

>> I have the impression PPP requires static observations for a longish
>> time, vs being able to produce a gpx of a moving receiver.
> 10 to 15 mins is considered the minimum.  Getting better up to about
> 24 hours of data.  There are services that will post process moving
> data, at less precision.  That is essentially the same as RTK.

And it probably needs the same kind of not having cycle slips as RTK.

>> I would like to get RTK working, but my impression is that one needs
>> unobstructed views and good signals, unless you get recent high-end
>> equipment.
> All GNSS receivers do better with better sky views and better signals.

Sure.  I meant that RTK doesn't really work at all without good views.

> No reason your base should not have a great sky view and signals.

My base is run by MassDOT, and has Leica stuff that I'm sure is very
spiffy.  So I expect high-end performance on that side of things.

> The main problem on a rover will be multipath, which is why "survey
> grade" receivers have the choke ring or ground plane.  The aluminum
> disk from an old 3.5 hard drive, placed directly under your antenna,
> will help a bit.

I have some metal to try.

> I don't see much improvement with expnsive equipment over a ZED-M9P.

I had some offlist conversations with a Trimble emploeyee, who claims
that their stuff can do RTK with tree cover, and sent me imagery where I
can't see the ground.  If you are succeeding at < 10cm RTK with a
ZED-M9P and some antenna under tree cover -- or even if in the open --
please post part numbers and I may try it out.

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