Network Rover vs Base/Rover

My experience has been totally different, you are limited by your radio. I have no limitations. You have to invest in a base, I don't. My State Dot provides me with a HARN (for free and if not I would gladly pay a subscription (versus the cost of another unit for a base)) and I get 3g and 4g almost everywhere. I was really skeptical in the beginning and then I got a project which absolutely required GPS. Now I can't believe I waited this long. And the beauty of this is that NSRS is only going to get better. Maybe I have regional advantage over you in terms of coverage/HARN. Looking back on it it's the best investment I've ever made.

Ralph

I'm with you Jimmy. Most of the places I work have limited cell coverage so not really an option. Frankly, most of my work is static/fast static anyway. I have corners that can be a 1 hour hike to get to so a 10-20 minute observation is no big deal.

Doug

We only have a couple areas with networks here. It's very nice to use, but only one of our GPS systems have the option. The other requires a base regardless. In areas where networks and cell coverage are good state wide, it would be a nice advantage. Especially on a large project, saving time on moving bases.

We work in rural PA...same experience. We mostly use our Trimble VRS as a control setter (pairs)...then set a base on the point. Cell service is sparse in many areas here, but it is nice having real time coordinates for stake-out jobs.
BTW, the base/rover set-up seems to fix faster/better than the VRS.

My experience is in line with Ralph's. the key here is that Network Rovers allow you to split units and use someone elses base. That doubles productivity. If you do not have cellular coverage then a regular base and rover will be your only option. I stay with verizon for that reason alone.

We've been doing a project in the middle of the Tappan Zee (the Hudson River at it's widest point, about three miles). We are out on a barge setting test piles.

We use the NYSDOT "Spider-Net" network. Access is provided free, just sign up and wait a couple of hours for approval and your password and access data. Of course, in the NY/NJCT metro area, coverage is probably as dense as anywhere in the US.

If not for the NYSDOT network, we'd have to have a base station which would need someone sitting there to watch it. Instead, both crew members are able to work together on the barge.

I'm a base and rover kind of guy. Out here on the sand bar our network is limited, and expensive!

I find the base/rover setup gives me much more flexibility for the type of work that I do ..

don't forget about the safety here don
we don't normally need someone guarding the base

i ran some soft control points with a guy who had the networked rover. at the time, he did not know how to do static (or they just had the RTK option, I do not recall). granted he could tag 8 of the 10 points we set in rtk and i could only hit 4 with the limited radio, but i hit every point static anyhow.

I have worked with it alot, and RIGHT NOW I like the base rover option. We are in Mississippi where almost all of our work is very rural. Right now, the cell modems/networks are just not as fast as a base rover setup. We spend say 20 minutes a day setting up the base and then the rest of the day we don't have to much down time from radios. We also have a cell modem that we can hook to our base and it's the same way, it's just seems a lot slower that a radio. On boundary jobs this isn't a big deal, but when we are topo'ing it gets old quick have to wait on the cell signal.

In the back of my head I know this vrs is making some surveyors lazy-er. A guy I worked for in college wouldn't process his own data from his base rover ( by the way he loved the "HERE" button ), I am almost certain he isn't going to download the base data of the internet and process anything now. It didn't take long for this kid to realize that this guy isn't helping our profession at all. I am glad i got away from that.

There is another option of using a GPS bridge that allows the user to get to those areas where the cell coverage doesn't cover. It utilizies the correction from the network and then you can use a UHF radio to rebroadcast in that area. Obviously the GPS bridge needs to be where it is connected to the network to rebroadcast but works great. The GPS bridge is about $2500 compared to about 6 times that for adding a base.

If you have a network that covers your work area, I would go with that option. Since joining a network, I rarely use the base.

Having said that, I have noticed that the short baselines used with a base/rover setup give more precise results than a network rover. Depending on where we work within the network the results vary. It is worth the time to do some mission planning before going in the field. This is all a matter of managing the speed/precision trade offs and requirements for each project.

The networks seem to be expanding outward faster than they become dense. This means that Surveyors will be using longer RTK baselines than we are accustomed to. I'm not an expert on the advantages of the different network schemes, but they all claim to mitigate the baseline lengths. My own experience leads me to believe that the distance is still a problem.

I can imagine a scenario where a small firm buys only a network rover and then rents a base when needed. A radio would also be needed for the rover. We have older receivers that we use for bases.

> I stay with verizon for that reason alone.

Yeah, I keep Verizon also, they are the most expensive but they definitely have the best coverage.

Ralph

Hey, you can always use both if you don't care about the fees. It's a good check.

have any of you noticed that the elevations seem tighter using a base and rover set up? My crews like to use the cell phone connection with no base, but have had projects where they didn't feel the vertical accuracy was as tight when they did so.
seems to me the shorter baselines would really only effect the horizontal positions -could it also be effecting the vertical?

Yes, the baseline length affects the vertical result as well. I have noticed the same difference between network and base/rover solutions. I would expect the vertical error of any RTK solution to be about 1-1/2 times greater than the horizontal.

What is an acceptable distance to still be away from a Rtn base and still use it or get a fix ?

The furtherest I have ever been away from a base and got a fix was 125 km, took about 10 minutes to fix and was just for a vineyard topo and had nothing to check the solution against.

We have 3 vrs networks here, one is 1600km away in Johannesburg , I have heard from one guy that he chose that network by mistake while working here in cape town and got a fix after about half an hour.

ah ha. sure would like to not set a base everytime, especially after the theft last year of our base and radio. For now, we'll keep using a base when we need our locations as tight as possible for design work.
thanks.

Question about virtual base set-up

The consensus seems to be that there is a bit more error in the virtual base/rover set-up than the base/rover set-up (maybe this is regional). With the exception of recon I can’t think of anything I do where I would accept more error. So why even use it.

If I’m staking Section lines or large tracts I really want the GPS to be working as tight as possible. And for smaller jobs, well, GPS often isn’t tight enough so I leave it in the truck.

What kind of job can you use a virtual base on? And if you use it is it as accurate as the close base/rover set-up? And if it isn’t then why bother?

I don’t work in and probably never will work in an area where there are any virtual base options but I just can’t see using anything that has more slop than GPS already does.

> ah ha. sure would like to not set a base everytime, especially after the theft last year of our base and radio. For now, we'll keep using a base when we need our locations as tight as possible for design work.
> thanks.

I think that's a pretty general statement, I don't believe it's true under all circumstances and it certainly hasn't been my experience. I will post some comparisons later.

Ralph