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Network RTK?

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(@j-t-strickland)
Posts: 494
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I am considering using gps networks, but based on the post below, I may be too far away. The closest bases to my office are just under 20 miles: Booneville, MS (Mississippi GCGC network), 19.2 miles west, and Belgreen, Alabama (ALDOT network), 19.3 miles east. But you guys are saying that's too far? I wonder what ALDOt and the other guys do, it's farther than that between some of the stations. There's no charge currently for use of either network.

I'm demoing SurvPC on my Algiz 10x tablet with windows 7 and Topcon Hiperlite + w/glonass rover, connecting with bluetooth. I can kind of connect to the networks (most of the time), but it takes a long time to get fixed, and I found one fix was off by about 5 feet. I have a normal AT&T internet connection on an internal aircard that seems to work OK. I read the sims card needs to be data only? Maybe that is part of the problem. Well, not with the range, I thought one could go out up to 30 miles, but I'm having a hard time finding any info about this.

BTW, the SurvPC version 4.03 crashes regularly. I hope this is due to it being a demo.
I get a message, "survpc has stopped working. A problem caused the program to stop working correctly. Windows will close the program and notify you if a solution is available."

Anyway, if my acceptable range is less than ten miles, then it's not going to be worth the expense of buying the software to run it. Maybe I read that wrong (nor for VRS?).

I've been using base & rover for several years, but the network has some advantages as you guys know. Or I thought it did.

I'm not sure about which mountpoint to use, either. some don't work at all.

I appreciate any help/ advise you can give.

 
Posted : February 8, 2015 1:23 pm
(@plumb-bill)
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If you are surrounded by reference stations (and it sounds like you are), then network can still do a very good job. You'll need to be sure to use a modeled solution almost all the time, though. This has drawbacks, as you won't be able to store vectors for inclusion in LSA, for example.

For topo and most stakeout, though, I don't hesitate to fire up the VRS. Even when the nearest bases are as far away as yours, if I'm surrounded by bases I routinely see cm or better performance.

 
Posted : February 8, 2015 1:29 pm
 Dave
(@dave-tlusty)
Posts: 359
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Network RTK? some results

> If you are surrounded by reference stations (and it sounds like you are), then network can still do a very good job.

I agree with Bill... "network can still to a good very good job". From a project here last fall, using the DOT WisCORS network, two different surveyors, two different network rovers, different field
procedures, different data collectors and software, on different days (about two weeks apart) observing the same physical monument in the road, while the road remained open to traffic produced the results below and we see minimal coordinate differences. This project was about in the center of a triangle of 3 WisCORS stations (about 30 miles between those).

The first line for each point is from multiple RTK GNSS observations (with pole in bipod) with a CHC X90 network rover. The values immediately below are from RTK GNSS observations with a newer model Trimble network rover (observation procedure unknown).

Langlade County Coordinates, NAD83(2011) datum

343410.4308,549719.4378,swx 193109
343410.4250,549719.4210

343473.0095,551732.4325,sQC 193109
343473.0003,551732.4340

343179.2308,554974.4171,swx 203109
343179.2700,554974.4150

342897.2346,557526.9320,sqc 203109
342897.2360,557526.8990,

342939.0633,560134.0426,swx 213109
342939.0430,560134.0190

342904.5110,562772.1640,sqc 213109
342904.4970,562772.1730,

342870.0323,565410.3963,swx 223109
342870.030 ,565410.428

342847.3041,568119.9298,sqc 223109
342847.281 ,568119.968

342822.3508,570829.5616,swx 233109
342822.348 ,570829.582

342473.5509,576265.9404,swx 243109
342473.562 ,576265.912

342847.3041,568119.9298,swx 193110
342847.281, 568119.963

The project was about where the red line is on the map below. The red tiangles are active WisCORS stations.

 
Posted : February 9, 2015 7:45 am
(@plumb-bill)
Posts: 1597
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Understood and agreed, but what I was saying is if he was that far away from base stations the modeled solutions would be of superior accuracy/precision. Also, if I remember correctly you cannot store vectors to modeled solutions, you have to go back to a single base method.

 
Posted : February 9, 2015 12:11 pm
(@kevin-samuel)
Posts: 1043
 

Network RTK? some results

Nice!

 
Posted : February 9, 2015 4:21 pm
(@the-pseudo-ranger)
Posts: 2369
 

With Survey Pro, you can store the vectors in network RTK mode, but all you get is the vector to the nearest station ... but I'm pretty sure that vector factors in the network solution (i.e., not "just" the vector to the nearest station, it's more like a calculated vector from the adjusted network solution to the nearest base).

 
Posted : February 9, 2015 4:31 pm
(@plumb-bill)
Posts: 1597
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Hmmm, I don't know about Survey Pro. I'm fairly certain that with Trimble Access, though, if you are storing vectors you are not getting a modeled solution.

 
Posted : February 9, 2015 7:21 pm