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MSM7 and higher resolution

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hpalmer
(@hpalmer)
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Just looking at difference between RTCM 3 MSM and MSM7.  There was mention that MSM7 had higher resolution. 

Has anyone quantified 'higher resolution' or know what higher resolution means?

Anyone using MSM7?

 
Posted : November 21, 2022 7:39 am
oldpacer
(@oldpacer)
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I think “extended resolution” would be a better term. I have no experience using the extended capacity of specific constellations. If I need better data, I still use old fashion static. In my opinion (and it’s just my opinion), MSM7 will help you if you have the bandwidth available and you only have two constellations. Whereas limited messages of full constellations, can’t be that bad. Six of one half a dozen of the other. Although it will allow you to get Glonass out of the picture.

 
Posted : November 21, 2022 8:14 am
hpalmer
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thanks.  Never liked results from Glonass.

 
Posted : November 22, 2022 5:09 am

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350RocketMike
(@350rocketmike)
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@hpalmer 

Should I be turning glonass off? I currently have everything turned on. Using CMRx.

 
Posted : November 28, 2022 6:35 pm
MI-Other-Left
(@michigan-left)
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I'm not aware of any Network CORS RTK provider(s) pumping out MSM7?

But that doesn't mean someone, somewhere is not doing it...

We've played around with GLONASS on/off while all others are on for RTK, static, etc.

Our experience makes it seem that most of the outcome depends on what the GPS system is doing. For RTK, having all on seems to resolve faster (but not much without GLO), but for static type work, the lack of anything other than broadcast ephemeris data for all but GPS/GLO kinda sucks.

Bottom line: GPS is still the foundation for most commercially available software/processing/RTK/etc, so anything else you can add, helps.

Caveat: I have noticed when we disable GLO, we get better battery life?!

 
Posted : November 28, 2022 7:06 pm
Rover83 reacted
Rover83
(@rover83)
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@350rocketmike 

In the past GLONASS had a lot more issues with accuracy and reliability. It's less of a problem these days unless you're chasing millimeters for high-precision geodetic work. When I did more of that type of work, I used to get better results processing GPS-only data, but that was for long static sessions.

If I remember correctly, you're also operating at higher latitude, where the higher inclination of the GLONASS SVs really does make a difference in geometry and can offset the slight decrease in precision.

You can test it out yourself by turning off GLO in your DC and comparing results, but in general these days if you've got full GNSS receivers running you're not going to see much difference, especially for RTK. If you're reaching for (and trying to maintain) lock under canopy every satellite helps.

All that being said, it's been a while since I've done any sort of testing, and about as long since I have done any really large, tight networks.

 
Posted : November 28, 2022 7:28 pm

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Jitterboogie
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You could also just collect all the data and when doing the network adjustment and cleanup turn on and off the various satellites.  We always collected all of them and did the analysis afterwards to see whose flying garbage cans were worse, the Chinese or the Russians.  It really did just depend.  It was interesting to see the difference in quality of the data sets between the different constellations for sure. That was a government job though too so the razor tight budgets weren't in the mix.

 

ymmv 

 

 
Posted : November 28, 2022 7:32 pm
350RocketMike
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@rover83 

Yeah I'm farther north than most here probably. I've had pretty good luck lately since I updated the firmware and gained ~10 satellites on the old r10. 

Stupid question about static....does it just mean your doing a PPP for at least 3 hours? Our crews that do a lot more legal boundary than me all have base and rover and usually do a PPP on a base point, which gets sent away for adjustment... everything else is tied in with the rover or ts. 

I only have a rover on vrs myself. 

 
Posted : November 29, 2022 3:12 am
350RocketMike
(@350rocketmike)
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@jitterboogie 

I should ask our office what they've noticed if/when doing this. 

 
Posted : November 29, 2022 4:49 am
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Rover83
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Stupid question about static....does it just mean your doing a PPP for at least 3 hours? Our crews that do a lot more legal boundary than me all have base and rover and usually do a PPP on a base point, which gets sent away for adjustment... everything else is tied in with the rover or ts.

Definitely not a stupid question, there are a lot of ways to approach boundary and GNSS.

For base-rover work, the base can be over a predefined, published position, in which case no CSRS-PPP (NGS-OPUS here in the USA) solution is necessary.

The occupation time for a PPP/OPUS solution varies depending on location and what the goal is for the survey. You can get a pretty solid position with as little as 15-20 minutes of data, and other times you are going to want several hours or more.

Obviously things work a bit differently north of the 49th parallel, but here in the USA boundary is all relative and doesn't necessarily need to be tied to a geodetic datum, so no matter what you hold for the base position, as long as the relative accuracy is solid and distances are ground, it's all good.

 
Posted : November 29, 2022 10:54 am
350RocketMike
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@rover83 

Thanks for the conversion from the Canadian acronyms to the US equivalent. Knowing that makes it easier to follow conversations about the subject, so I can start to understand things better.

We used to always use the "here" position and send away the PPP for integration. Now what's being done sometimes is shooting with VRS (CANNET) first and setting the base on that point for the job. Or the guys that have VRS only (like me) can shoot at least 3 points on the job and integrate it that way. 

If a job is just a locate, then coords can just be local but they want to have at least a rough UTM coord, even if off my phone GPS) but typically there usually is no reason not to at least set control in UTM first and then set up the robot on that. 

It's usually just when we're doing a job that's tied in close to an old job that we use local coords. 

This post was modified 5 days ago by 350RocketMike
 
Posted : November 29, 2022 3:37 pm