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.
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> 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.
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> 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?
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> 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.
What Consensus? How did this become a consensus?
Here's a study done by Texas A&M, which uses a large enough Population Sample (A whole city) to draw some realistic conclusions and not conjecture.
That has been my experience almost to the tee.
Ralph
Question about virtual base set-up
I'll suggest that the solutions of RTN depends on just what type of network each is using. I'm thinking that in the NYC area, the network is fairly dense, with baselines under 10-15 miles. Here in Arizona, what's available for networks is usually much greater distances between stations, so perhaps that's why we experience a lesser degree of accuracy, especially in the vertical. I'm still learning what works best for us, and appreciate the input of others with more experience and in different conditions than myself.
Question about virtual base set-up
> I'll suggest that the solutions of RTN depends on just what type of network each is using. I'm thinking that in the NYC area, the network is fairly dense, with baselines under 10-15 miles. Here in Arizona, what's available for networks is usually much greater distances between stations, so perhaps that's why we experience a lesser degree of accuracy, especially in the vertical. I'm still learning what works best for us, and appreciate the input of others with more experience and in different conditions than myself.
I agree with you Joe, I think I'm fortunate to be in area which very well populated. So it's probably more of a regional thing as Mr. Schrock pointed out above.
Ralph
Question about virtual base set-up
A useful piece of research, conducted by Newcastle-upon-Tyne University is available on the UK Survey Association website:
www.tsa-uk.org.uk/guidance.php
Tick the box labelled "Full Report", fill in your details and click Submit.
The research used a number of known UK GPS reference stations and treated them as survey points. It records in great detail the variations etc. found. 150 pages of bedtime reading.
Question about virtual base set-up
> A useful piece of research, conducted by Newcastle-upon-Tyne University is available on the UK Survey Association website:
>
> www.tsa-uk.org.uk/guidance.php
>
> Tick the box labelled "Full Report", fill in your details and click Submit.
>
> The research used a number of known UK GPS reference stations and treated them as survey points. It records in great detail the variations etc. found. 150 pages of bedtime reading.
Thank You Chris,
I believe I read this already. Good Stuff!
BTW my key board keeps getting stuck on me and I keep posting these incoherent sentences, I apologize.
Ralph
Z error estimates
H error half of Z error
RTN - 1 - 3 epoch observation + - 0.14 ft in Z
RTN - 5 - 3 epoch ave. observations + - 0.05 ft.in Z _______________________________________________________
BASE - ROVER 1 - 3 epoch observation + - 0.05 ft. in Z relative to the Base < 1 mi
BASE - ROVER 5 - 3 epoch ave. observation + - 0.03 ft. in Z relative to the Base < 1 mi.
_____________________________________________________________________________________
Pick your poisen
Why would you need someone to watch your base? Last summer, my party chief and I would set up our base almost daily on an ASCM located maybe 20m away from a beach volleyball court at a very busy park in Fort McMurray, Alberta. In the entire month we were in that part of town, the only trouble we ever had was when our base's internal battery would die, or when someone managed to jam our channel using an external radio... (we were using a Topcon HiPer setup of some sort...)