quick RTK Base/Rover question
I have two R8-3's (GPS+GLONASS) and just purchased a used R8s (GPS+GLONASS+BEIDOU+GALILEO). My initial plan is to use the Model 3 as the base and the R8s as the rove,r thinking that the rover is the one most dealing with possible obstructions and the radio would be the same from either.
Does that make sense?
I'm not sure if it really matters, but I'm thinking I want a correction based off the same constellation of sats. As opposed to the base sending a correction based upon GPS + Glonass while the rover is applying the correction to a position based upon all four. If you do benefit from having all four at 1 unit would it be better at the rover or at the base? I have no idea. Intuitively I would use the 4 constellation unit at the location expected to have the most difficult sky view, whether that be the base or rover.
Presumably the base would be in a pretty wide open area, so I'd put the R8s on the rover.
I don't think the RTK base determines a single correction based on all of its available constellations. I think the corrections are computed and transmitted per constellations. I'm not going to get better results using a four-constellation base when the rover only has GPS.
To improve RTK results you need to increase the number satellites seen in common by both base and rover.
Since the solution should be based on common satellites, you will only be using GPS and GLONASS in determining positions. My initial suspicion is that it wouldn't matter which is rover or base because the constellations being tracked for a solution will be limited.
I do wonder if the radio and/or processing might make a minimal difference. Does one have a better radio for transmitting corrections than the other? Is one unit considered to be able to better mitigate multi path during processing (even when limited on the constellations)? I'm not familiar with the units, so I don't know the answer to those questions.
Thanks, all. Good food for thought. I do admit I can't see how I'd have any better precision with either setup, but thought I'd have more opportunity for a fix if my rover had more access to sv's. Maybe from what some suggest it wouldn't matter if the fix is dependant on using only the same constellations. I'll try it both ways if I return to a site I've already used it on in one configuration and see if there's any difference. Even if no gain, one of my R83's is having power issues, so maybe just look to a time for more access down the road. Mahalo.
I think of it this way: with a base/rover config, it’s like your rover is “on a string” and the corrections on the rover are tied to the base station. With differential corrections, you’re only as good as the corrections coming from your base that are “pulling” your rover into its precise locations. And because of redundancy, you’ll need the same constellations available at each antenna.
If you want to tighten up your obs later, you could run your static base sessions through OPUS and or TBC. You could try the same with rapid static sessions on your rovers. For for true real time performance, “it’s all about the base”. 🙂
Use the one with the most powerful radio as the base - you will get the best range.
Also for a rover to use a particular constellation, that constellation must be being processed by the base. If it is not set for, say Glonass, then the rover will just ignore the constellation even it is enabled. So you want your most widely optioned unit for your base
Also with Trimble, the ability to be a base station is an option enabled at purchase - so you may be limited with your second-hand units
Only satellites observed by both rover and base can be used. Since the R8S does not have ProPoinr (faster fix) there’s no benefit for it as a rover. It can only broadcast at 0.5 watts. It’s essentially equivalent to the R10 model 1. Remember you need to have a FCC license to broadcast RTK signals. Are you sure your R8-3 doesn’t have Galileo? That’s the reason the model 3 came out - Galileo.
