Guys, I have been running a Sokkia GRX-1 base and rover system for the past 9 years.?ÿ I have a Ranger 3 running Survey Pro with an AT&T data plan to connect to the GCGC local network in Mississippi to get a GNSS SPCS base point for my base station, and then switch over to my base and rover system for field work.?ÿ We have pretty good cell coverage around here, and there has only been a few times in certain areas where I need to occupy my base station point and collect OPUS data for a good SPCS base point.?ÿ I have a workaround if I need to do stakeout work with an autonomous base setup.?ÿ I also use the onX-Hunt app on my Samsung smartphone to get somewhat close to section and property corners when doing rover work.
I have had good results through the years, even under some light overhead canopy situations.?ÿ I utilize GPS and GLONASS satellites, and out in the open, I can track anywhere between 12 to 15 satellites, no problem.?ÿ I can cover a lot of ground riding large survey fence lines on my ATV, and getting off for a shot on the fence line or getting an open ground shot with a tape measurement over to the fence line.?ÿ Fence corners, or monuments found under canopy is where I run into a few problems.?ÿ ?ÿI need maybe 9 satellites to get a slow "fix", but I need 10+ to fix faster and better as long as my PDOP is good.?ÿ Under canopy, I can track up to 6-7 satellites with an autonomous solution, but playing with a 15-foot rover pole, I can run the rover unit up and down until I find that magic hole in the canopy where it will start tracking 8-9-and sometimes 10 satellites.?ÿ Once I get to tracking 8-9 satellites, my units start "roving" and finally, after about 5-10-15-20 minutes and picking up #10 and sometimes #11, I will finally get an "RTK fixed."?ÿ ?ÿIt just works better and faster with 10+ satellites being tracked.?ÿ Many a day, after spending 30-45 minutes trying to get one point, I consider going out into the open, setting two points, and use my total station to traverse in to get the point that I need.?ÿ Sometimes, this would require many setups, and I am stubborn enough to try and let the GPS do its thing and "FIX" where I am.?ÿ ?ÿOver the years, I have learned how to play with the rover unit height and find that hole in the canopy, or moving around the area where I need my point and set two points where I do get a fix, and using my total station to get the point I need.?ÿ As long as I can get my ATV near my point, everything works OK.?ÿ It is the long hikes to inaccessible by ATV areas that take time.?ÿ My base station is hardly ever more than 1/2 to 3/4 mile away, so the UHF radios work OK unless I get in a heavily wooded creek bottom lower than my base station with heavy overhead canopy.?ÿ I try to do these jobs in the winter if the client can wait.?ÿ My system works fairly well in the winter time with no overhead leaf canopy.?ÿ It does NOT like evergreen cedar trees and pine trees.
Considering an upgrade, I have read through some of the threads on here trying to get a feel for some of the new equipment.?ÿ A friend of mine recently obtained a new Topcon Hyper VR system with a FC-6000 field controller.?ÿ The GPS unit is similar to the Sokkia GRX-3 unit, I believe.?ÿ He really likes the system, and says that he gets a "fix" in conditions where his old unit did not work at all.?ÿ I am considering either keeping what I have or upgrading, and I am wondering if I will see a marked improvement in getting faster fixes in worse conditions than I am now.?ÿ I really do not want to spend an hour getting one point, I want to grab and go.?ÿ But, will paying for a new system really be worth it??ÿ I am 65 and slowing down, and I am a solo operator doing a little engineering work and have more surveying work than I want. Getting out of the field and back into the office will help with time spent on a project, but I really enjoy getting into the field and away from the telephone and computer!?ÿ I like to?ÿ concentrate on the larger tracts of land and estate divisions, getting a mix of open fields and wooded tracts.?ÿ I figure that I will save many hours in the field with a biggerbetterfaster system.?ÿ Some say theirs will "fix" in a basement (yeah, right).?ÿ I would like to have a system that will save more time in the field than I am getting right now, but a new system is going to have to do much better in the time category than I have now in order for me to pull the trigger. Recommendations?
I am looking for comments, recommendations, experience with upgrades, faster fixes, tips, tricks, techniques, and general input from experienced people.?ÿ Thanks in advance.
My experience is while you can get fixes under canopy with GPS/GLO or full constellation systems (in my case Leica 1200 vs GS14s) if you set reliable points in the open and then measure the same point with total station there is a lot more variance than the CQs indicate (even with doubling them to get closer to 95% confidence interval). The 1w radio satel on the gs14 is better than the old 'bottle' 2w pdl, not light years but better.
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For topo at the 0.05m-0.1m level this may be acceptable but where I work you need to measure boundary monuments to <0.02m and the only way I can reliably do that is to set a GPS/GNSS pair in the open and shot the corner under canopy. And out in the open an old GPS/GLO system will still obtain similar precision to a newer set.
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Depending on the precision under canopy you need and if you think your current gear will last till you want to stop working I be thinking very carefully if it is really worth the investment. It'd be a no brainer if the gear is near dead and you wanted another ten years of use but anything less...
If you're spending 30-60 minutes trying to catch an RTK fix, you'd be much better off collecting Static data at the Base and Rover for a more reliable solution.
I suggest you keep the GRX receivers and purchase two new VR's. Setup the base in wide-open secure area for RTK and Static. Then place the other three receivers at dense canopy areas to collect static simultaneously. In my experience, so long as you're not in conifers, this yields better results.
It doesn't sound like you are doing big field to finish projects, or having to stake a bunch of roads, so why go with Topcon?
There are a number of my cheaper options, including ones that advertise on this page. I would think Javad would be perfect (Think half the cost of the Topcon setup...and you don't have to have a Topcon!)
Oscar, Emlid, Trimble (which is also expensive, but good) etc all advertise here.?ÿ
Come to think of it, if the company doesn't advertise on this site, they are pretty suspect.
Oh, and to answer your question...yes the tech over the last 10 years has made enough of an advancement to make buying something new worthwhile. If you can afford it, it appears that the IMU tech is advanced enough to be worth looking at as well.
The "tilt" tech from a few years ago is worthless in my experience. We had units with this "feature" but none of the crews felt it was worth the constant calibration, so it never got used. The no calibration IMU appears to be a completely different kettle of fish.
Harold, excellent, well written OP.?ÿ You are singing my song, and I am only 51, though.?ÿ Watching this thread with interest.
https://m.youtube.com/watch?v=rZFwmpmw5fQ
Well worth a watch to temper your IMU expectations. Great for topo/setout, not for bounday/control (unless just rough boundary staking)
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Nuff said.
Nate
What sort of repeatability are you getting in that situation, not just GNSS double ties but shooting perfect GNSS points in the open and shooting it with the gun?
0.02m? 0.05m? 0.1m?
Thanks
My typical is around 0.05'. Javad LS has a fairly rigorous process, so that each shot is a combination of resets, and about 500 epochs, and more resets. My opinion is that 1 in 10,000 shots are bad, by 0.7' with this process. This kind of shot is most always near a large tree trunk. Typically, the LS gives you a visual cue that something is less accurate called a string line, where you can see the point cluster error ellipse is long and skinny. Like 0.10' x 0.22'. This we call a string line shot.
So, if it's a boundary point, and there is a 32" oak, or pine, 1 foot southeast of it, shoot it 2x or 3x. This eliminates that one point in 10,000, and, typically, awful places like that cause a shot spread of 2 points being 0.12' apart, and one is 0.04' from one of those above points. (I take 3 shots if it has lots of big trees nearby.)
It works well.
Nate
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Good to know, are those verified with total station or just repeat GNSS obs? Easy enough to get the GNSS obs to match but when you shoot in from control in the open result can be startlingly different.
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My old boss had a pair of Javad LS and using the standard boundary profile couldn't get anything like those precisions. More like 0.1m or so if it would even fix under the sort of canopy in that photo. Still had to use the total station for anything critical under canopy. In a very different geographic location (New Zealand) but still can track 12-15 GPS/GLO birds usually.
While it is true that:
You can get more shots faster with a nail in the field, a robot, here is the typical tradeoff.
It takes 5 or 10 or 15 minutes per point, (some of these are multiple shots) and you have typicly 0.05' of error. If the error ellipse (shown graphicly as you work) is excessive, or if it's a critical point, observe it multiple times. Javad has a great averaging program. It does a weighted average. Basicly. If you can stand some time on the point, and some hundredths of error, it's Kent Millimeter in a can.
Here you see the unit up and to the left of the ATV. It might a took 20 minutes on this point, but I strive for a >0.05' (less than 0.05') on everything. I have the old LS, and only 2 constellations in it. I've ordered a new base station, so I can get 4 constellations, and some 30 satellites with it. This should cut time some. Later, I plan to get my LS upgraded to the PLUS model.
I don't make anything off telling this. I truly want to see professional surveying made better.
?ÿThis is a normal picture.
Nate
If you really want to SEE it for yourself, get a sheet of osb or plywood. Drill holes in all 4 corners, at 0.10' from the sides. This makes 4 holes that are 3.80' and 7.80' apart.
Add two extra holes at the middle if you like.
Now, go nail it down in a gnarly hole, under some terrible canopy.
Then call a javad junkie like me, and tell them to shoot all 4 corners, one time. Have the junkie name them by his estimated accuracy. Then have him re run it, and average it.?ÿ
(Keep the pole oriented the same, to eliminate a poorly adjusted bubble issue)
This is going to tell you a lot.
Proof is in the pudding.
Nate
I'm 80 and slowing down too. Staying with the Leica 1200 for now but I'm willing to listen.
Bruce, thanks for your reply.
At 80, it's harder to learn.?ÿ
In AZ, you have lots of sky. If you are good at learning new tricks, ok, but if not, stay with what you have. You won't see great gains, in the wide open.
Nate
