Existing Sokkia GRX-1 base and rover system. Upgrade or not?
Guys, I have been running a Sokkia GRX-1 base and rover system for the past 9 years. 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. 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. I have a workaround if I need to do stakeout work with an autonomous base setup. 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. I utilize GPS and GLONASS satellites, and out in the open, I can track anywhere between 12 to 15 satellites, no problem. 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. Fence corners, or monuments found under canopy is where I run into a few problems. I 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. 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. 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." It just works better and faster with 10+ satellites being tracked. 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. 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. Over 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. As long as I can get my ATV near my point, everything works OK. It is the long hikes to inaccessible by ATV areas that take time. 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. I try to do these jobs in the winter if the client can wait. My system works fairly well in the winter time with no overhead leaf canopy. 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. A friend of mine recently obtained a new Topcon Hyper VR system with a FC-6000 field controller. The GPS unit is similar to the Sokkia GRX-3 unit, I believe. He really likes the system, and says that he gets a "fix" in conditions where his old unit did not work at all. 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. I really do not want to spend an hour getting one point, I want to grab and go. But, will paying for a new system really be worth it? 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! I like to concentrate on the larger tracts of land and estate divisions, getting a mix of open fields and wooded tracts. I figure that I will save many hours in the field with a biggerbetterfaster system. Some say theirs will "fix" in a basement (yeah, right). 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. 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.
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.
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.
Come to think of it, if the company doesn't advertise on this site, they are pretty suspect.
Harold, excellent, well written OP. You are singing my song, and I am only 51, though. Watching this thread with interest.