network rover to base station and rover question

That shouldnƒ??t be a problem.?ÿ

Thank you?ÿ ?ÿ

I was hoping it wouldn't make a difference.?ÿ?ÿ

That shouldn't be a question!

How did you learn to use GPS, do far?

I would only warn that you are unlikely to be able to place the Base Ant precisely over the same control point, especially the height of course.?ÿ So be ready to do some slight offset adjustment in order to match things up.?ÿ

This thread is disturbing, but it seems to fit a pattern.?ÿ

Posted by: DC Kelley

I would only warn that you are unlikely to be able to place the Base Ant precisely over the same control point, especially the height of course.?ÿ So be ready to do some slight offset adjustment in order to match things up.?ÿ

Can you elaborate on this?

Before more folks jump on the OP for asking a question that might seem elementary to some, I'll note that he's been using a base-rover setup for many, many years and only recently upgraded his equipment to a system that also provides network rover capability.

Depends on how tight your control needs to be and how good the rtn is in that area and how long your base will occupy the point.?ÿ Sometimes I will start with an rtn position so that I can get going fast and on the system.?ÿ But then will update all the points based on a hours long base session.?ÿ This will give me much better control than the rtn in my area. Usually nearest CORS is 25 miles or more away for me, so rtn rover positions can be a tenth or more different horiz and worse vertical, and sometimes can't even get a good position rtn although I will get several "fixes", but position turns out 2 feet wrong or more when checked with local base/rover and/or total station.

?ÿ

2 feet? that's really bad, more like an autonomous position.

Posted by: MightyMoe

2 feet? that's really bad, more like an autonomous position.

Agreed...100%

Something must be wrong.

Duane is using a Javad LS. They are said to not give a bad fix. Didn't Mr. Javad have a $10,000 reward for anyone that could prove a bad fix with the LS Receiver?

Duane you best collect your reward. LOL

? The OP was a good question, it's you other guys not understanding the complexity of rtn or rtk for that matter.?ÿ A bad fix can easily be worse than an autonomous position.?ÿ In fact when using trajectory mode for woods roads I will set it to autonomous to avoid getting the occasional position 20 feet off.?ÿ

When I say a got 2 or more feet off using rtn it is just for testing to see why I find those kinds of errors/mistakes in other surveyors' work.?ÿ I believe it's coming from bad fixes they accept using the rtn.?ÿ I can prove that theory using any equipment, not just JAVAD.?ÿ But yes, even JAVAD will let you get bad positions if you want it to, or if you don't know what you're doing (hence the 10k reward offer was retracted I think).?ÿ

But with JAVAD it's not guesswork or return to every point for a second shot to make sure (which apparently is not happening or I wouldn't keep finding the mistakes); I know if a position is bad and can reject it.?ÿ

The source of these large errors is multi-path.?ÿ This is usually worse for rtn work because the base is usually further away, which would require much more time on point than local base in order to resolve ambiguities.?ÿ

But yeah, all that stuff gschrock mentions is important.?ÿ From my experience though, the real problems happen after people get all the settings correct and know they are getting correct positions.?ÿ After that they start pushing it and accept positions that really aren't any good even though they have a few "fixed" solutions.

My experience in upstate NY the amount error can often to point the problem.?ÿ

I follow a lot of surveyors control when I set up projects for machine guidance.

• ~2'H error points to International feet vs. US survey feet
• 3.8'H points to double correction NAD83(2011) on a RTN
• ~110' elev points to no Geoid
• ~3.5 in H, has been my experience in a bad fix. I have seen documented just two know bad fix using Topcon base/rover in the past 18 years. Both were under heavy canopy, and questionable RTK conditions. So I knew to reset and double check.
• ~10'H and 20'V points to an autonomous position
• ~.10' to ~.30' points to users establishing a two point base with GPS on grid. Then traverse with EDM without CSF correction, and some angle error.

I don't understand the OP's question. If he is familiar?ÿ with RTK GPS, be it RTN or Base/Rover, it doesn't matter on a single project so long as he uses the exact same GPS parameters on both setups. I will get an RTN on a single point. Place my base on that point. Then RTK and Static at the same. Using OPUS I will later verify the RTN location.

I never use RTN in adverse conditions (multipath). When I do use the RTN it is for only a single point on any given project, my BASE point.

I mostly use rtn for base position as well, but if the base is there for a couple hours I'll use positions from the post processed base solution as they tend to be better. Also, if get far enough away that radio connection is lost and still want real time then I turn on rtn if I have cell coverage.

> gschrock, concur, and certainly common for the Caster operators I know.
> Duane Frymire, concur.

My own original reply here was limited to observing how hard it is to setup a tripod at a specific mm precise height.
When I hear "2 feet" my first thought is two different datums are in use. Lots of otherwise smart people forget to confirm the frame of reference in use by different devices. And while this board is mostly US focused, the this is a common problem when the Base stations are run by different folks with different needs and multiple local projections. But of course you only see it with single baselines, not network solutions.

Thank you Jim Frame !!!?ÿ

Ok, I did set up the base over one of the control points obtained from the Network.?ÿ

Then checked into everything possible.?ÿ Horizontal from zero to 0.03' position wise. Vertical ran about .02' t0 .05' (not bad)?ÿ ?ÿThe reason I wanted to use the base at this site was due to high tension power lines kept interfering with the MiFi device.?ÿ ?ÿThe base / rover set up is very fast and efficient.?ÿ I was extremely pleased.?ÿ ?ÿBUT WAIT there's more.?ÿ After the job was staked, (just an old flat rock drain) ,?ÿ I set up the topcon robotic and shot that same control shots as before PLUS some of the stakes.?ÿ Amazingly, the robot shot verticals in between the 2 GPS runs and horizontal was about 0.02'?ÿ ?ÿ(still on the stakes)?ÿ ?ÿ Thank you for the Advice (and confidence) to add another weapon to the mix.?ÿ

Yes Jim Frame is correct.?ÿ I've been using Olde Tyme Trimble 4000's?ÿ (se and ssi) since 1994?ÿ ?ÿBack when we had mission planning and needed to do jobs at 10 o'clock pm to 1 AM just to get enough satellites.?ÿ Ah the good old days ("_")?ÿ ?ÿ

Glad I found that old matchbook cover with the ad "Become a land surveyor"?ÿ ?ÿgiggle giggle?ÿ?ÿ

Thanks again . . . . . ."It worked" !!!?ÿ

I too use two base stations and a rover and post process everything.?ÿ I must be a dinosaur.