Since I see that Gavin is posting here, I will ask some questions that others may have, and maybe Gavin and others can chime in...
When I use the WSRN (Network RTK) (Puget Sound sub-net usually) I have noted the following unsubstantiated, unscientific, undefined things:
GPS+GLONASS gives a faster and more consistent ability to "go fixed", especially in challenging enviroments.
GPS ONLY, if there are adequate satellites gives a more accurate fix, both in my observed repeatability, and in the HRMS displayed.
So...
using a Topcon GR3 (with latest firmware update), with an ATT sim card and an internal GSM cell modem, running Carlson SurvCE 2.5x (latest version)...
(Meant to say that this was my experience for this firmware version and the previous version as well.)
If I set up my own base station, this is not observed by me. The GLONASS+GPS solution on my standalone base is always better than GPS only.
Questions:
Am I imagining things?
Is this a possible interaction between my receiver and the Network?
Is there a flavor of corrections that works better? (CMR+, RCTM3.0???)
Comments?
I have heard comments that GLONASS can degrade precision, is this true in your experience?
Not trying to expose weaknesses in the system, I love WSRN, just thought it might be a good topic for general consumption.
Actually spoke a few minutes ago with another user of WSRN who found that using RCTM3 was preferable to CMR+ when using GPS+GLN...
My experience is that it also depends on which base station you are primarily tied to, meaning that getting a new VRS solution with a new ???(I know you dont call it a master auxillary, but whatever it is) seems to change the precision at times.
And, I kind of misspoke about the single base, what I meant was my own standalone non-network base...
Thanks for your comments.
This stuff all works, but we need to have a deep understanding to be experts and to really know what we are doing...I am trying to get there!
My limited understanding of the situation is that Glonass will add more satellites and thus allow for faster initialization and also allow for solutions when there are less regular GPS satellites in the observable sky. Also the precision of Glonass solutions are generally less than the US system gives so I would expect the RMS values to increase when mixed solutions are used.
Gavin, right you are, not all hardware is created equal by a long shot, you are in a tough spot trying to run a RTN with a mixture of hardware.
I have always thought the brand I use is the best, doesn't everybody? However, I consult with a lot of other surveyors and aerial mapping firms, sometimes I post process using the software my vendor sells, sometimes (more often than not) I use a vender independent software, when you do that you quickly learn that there is some makes that plain have noisy data, you see stuff that you would never know was abnormal if you didn't work with a lot of different data sources.
As it turns out, the brand I use is the best 🙂
On the subject of RTN's, I don't think any I have used give as good of result as running my own nearby base, especially in the vertical, so I don't think the situation the OP described (using his own base vs the WSRN) is unusual, YMMV and I hope it does.
SHG
The fact that the local base typically gives better RMS values makes sense in that your corrections are being modelled from an actual base that is likely much closer to your rover than the bases in an RTN.
Shelby, what independent software are you using?
I may be interested in testing, however most of my work in WA is post-processed using WSRN (or other) CORS, in fact I have so little need for RTN that the cost hasn't been justified for me. That of course could change depending on if I get the right number and kind of projects in any given year.
I did do some testing along the border with OR last year when I had some strange results, but that was with ORGN, however as you know there was some shared data streams.
SHG
I use Waypoint Consulting's GravNav product.
Will convert and process almost any native file.
SHG
Gavin, I didn't mean to imply that using a RTN wasn't a good idea or even cost effective tool, it is just that since I don't work on the ground in WA that often, it is just more cost effective to PP static data using the CORS or my own base when I do the occasional project. On top of that, the bulk of my work there in recent years has been PP airborne flight trajectories, a RTN isn't useful for that at all, in Oregon I use the RTN occasionally, but then again so far it has been free to all users so is cost effective for the now and again user. I have paid for short term subscriptions to other RTN's when doing enough work inside their footprint to justify the cost. Leica is getting a pretty large footprint with their North American network and is the one I try to use when traveling just because I am familiar with it, I think they now have 400+ CORS running.
My business model is to support aerial mapping projects and to be mobile. Some people diversify the type of services they offer, I limit the services, BUT expanded the geographic area, because of that I could use and have used data from a large geographic area of RTN's, but that is expensive on small projects, so more often than not I just run my own base station.
Are you coming down for the OGUG workshop on 11-Jan-2012 in Albany?
Merry Christmas!
> Like to be part of some tests next year? We are spooling up new servers and RTN engines early in 2012; I need to do some serious testing on that setup before wide release.
Gavin, I will give you a call about this sometime after New Years day. It may tie in with my upcoming project. How we doing on those truth coords for RKD1? That would be a nice Christmas present 😉
Have been following this thread closely, it is going to be good knowledge for me. Good questions, answers and discussion.
Happy Holidays! BC
:good:
