Hey everybody, this is my first post here.  I'm curious if any of y'all have recently purchased the L5 Tracking OAF, and if so, did you notice any difference?  I realize that we don't have a full constellation yet, just curious what sort of results you're now seeing, especially in challenging environments.  The overwhelming majority of surveying I do is in Appalachian jungle, but I've seen pretty good results from my Topcon GR-5 with just GPS/GLONAS under the winter canopy.  I feel like it'll eventually be worth the $900 upgrade, but I'm not sure whether it'll make the difference in getting a fixed position in places where I'm currently only getting an autonomous solution. 



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Welcome Kurt!

I'm working daily with full GNSS receivers (base+rover equipments) and I realize, the biggest improvements are consequent to the build up of the Beidou and Galileo orbital segment.

In many sites, with a lot of obstructions, more satellites can reduce dramatically DOP values ....

Advantages of L5 should be:

  • increases the safety of system (is less attackable by jammin)
  • combination L1/L5 improves the estimate of ionospheric bias
  • L5 code wavelength is 10 times shorter than L1 C/A code wavelength (may improve accuracy in noisy conditions)
  • due L1/L5 and L2/L5 combination, theoretically the RTK FIX come faster ....
  • chip code on L5 is longer and its may improve performance where are obstructions and multipath

Cause the satellites with L5 are few, is difficult to compare the performance with 3rd frequency and its improvements with the contribution of Beidou and Galileo.

Have a nice day!

Carlo Alberto

Outstanding! Thanks for the reply. Yeah, I'm still experimenting with RTK in challenging environments, and right now I'm trying out the Topcon VRS network. My main enemy is getting a good 4G service in remote mountain National Forest areas. The Topcon rep told me that BeiDou isn't supported in their network yet, but it will be in a year or so.

So this might be a dumb question, but would I need to upgrade my Base unit in order to reap the benefits of L5 as BeiDou (in areas where I can't get VRS, obviously)? My base has GLONAS, and in almost all cases I set the base up in areas with really rockin' sky. If I can get by with just upgrading the Rover then I could afford to buy a 35 watt radio.
Also curious, how many epochs are you averaging per shot?

My normal MO is to set up, wait for fix, take a 20 epoch shot, reset RTK, take another 20 epoch shot, reset, take one last and then start inverseing... I haven't really done the math to see what would be an acceptable tolerance, nor have I ran the least squares program afterwards. I'm just used to giving a thumbs up at 0.02 with my robot so that's my instinctive tolerance.

Just curious what y'all think is an acceptable difference in shots. I mean, I've seen points differ by 0.02' and maybe as far out as 0.07. I reckon any of those would fall on the cap of my aluminum USFS monuments, so that should be fine.

I live (almost exclusively) in the retracement survey world and stake-out world. Retracing hundred year-old surveys, and marking/blazing property lines. I've done nearly 100% of this with my robot; never RTK for a solution for anything other than a pair-of-points.

The day I can survey exclusively with a GPS receiver is the day my job changes drastically. Gone will be the days of chainsaw crews just to traverse! I feel like I'm living in a dreamworld thinking like that, but I'm 34 and I reckon technology will allow me to do that at some point in my life. I'm halfway thinking that if I use my head and save my bigger projects for the winter that I might be able to get away with more GPS than I think...

That's the real angle of this thread: trying to learn how to use my equipment to my advantage!

Im really looking to get into Robotics, are there any instruments or data collectors you can recommend to me? 

I have been using robotics for 20 years or so. I have used Topcon, Leica, GeoMax, Geodimeter, Spectra Physics and Trimble. I did not have good experiences with early models of the Trimble or Spectra Physics so I have stayed away from them. The Topcons were adequate but somewhat slow and finicky locking on target. The Leica is exceptionally fast does not require any type of "active target" or any attachments to the rod to help find the prism and I have had excellent support from Leica staff. GeoMax is also an excellent robot and is comparable to Leica at a lower price point. As far as software goes I have used Carlson, Survey Pro, Magnet and Field Genius. My pick is Field Genius it works with most equipment except for the newer Trimbles and they have great tech support. Field Genius is very powerful for both land surveying and stakeout. As far as controllers go my favorite is a Mobile Demand windows tablet with 4 gb ram that has been used daily for over three years and no problems. Pricey but well worth the price if speed and large bright screen are needed. On the less expensive side I use GETAC PS 336 they are sturdy reliable. I also use a Ranger 3 which is comparable to the Getac in performance but has a better keyboard but cost more.

I've used a Trimble S6 and few different Topcon robots and I'm not sure which is my favorite. The Trimble is the smoothest operating machine that I've used, but I think you're stuck with Trimble hardware/software. My Topcons have allowed me to use non-Topcon stuff, like a Panasonic FZ-M1 data collector with Carlson, but it does not play well with my robot. I love that setup, but I need to spend some time ironing things out before it's really good. The Panasonic runs Windows 10 and has an amazing processor. The only true negative is that it's a stylus-only device. When you're doing a topo survey it's handy to have an actual button to "take the shot"...especially when you're taking a shot every ten steps.

I've got a Topcon Tesla, which might look nice but it's another Windows Mobile turd with a lousy processor. It hangs up and needs a hard-reset too often for what they cost. Nice screen size, but that's about it. Topcon Magnet software has grown on me, though it isn't perfect. It seems good for a retracement surveyor working in the woods. The icons for taking offset shots are tailored perfectly for a dude taking shots to the center of trees. Also like the feature that allows me to press/hold on the map and "find me here". The gun will turn and face that spot and start looking.

The Topcon robots with the RC-5 are pretty slick. Press a button (either in the data collector or a physical button on a device mounted atop the 360° prism) and the gun begins looking for you. The rod sends an infrared beam to the gun and it searches until it finds the glass. It does it pretty quick too (better if you're further away). Very sweet, and it works well in the bushes - handy for one-man operation.

The Trimble auto-lock instruments are amazing too. If you're doing a complicated topo in the woods you can work quickly with a man standing beside the gun. When it loses you they can redirect the gun in your direction and it'll automatically lock back on to your glass without having to go thru some searching routine. That's also bad though...can't tell you how many shots I've made to the taillight of the truck as I pass by it and inadvertently let the instrument lock onto it.

The Topcon uses little gears to rotate, Trimble uses some kind of silent magnets. Trimble wins the buttery smooth award hands down. Both of them were 3" instruments: plenty for retracement surveys (each is available in something more precise though).

Here's a pro tip: Best traverse results have come from sēco eclipse nodal prisms. Robots lock onto the prism in the exact same spot, so it's critical that your rod level bubbles are calibrated often. The nodal prisms stack the point over the center of the rod irrespective of how the glass is tilted (up/down/left/right) from looking dead at you. Those have been a great addition to the gear.

I think once you pick a brand you're pretty well stuck. You take a beating on trade in, and I'm not even sure you could trade a Topcon in for a Trimble... You'd be better off trying to sell it on your own first. Might check out Leica...or some of the other brands.

The Topcon FC-500 looks like a decent data collector. It's supposedly got a stronger processor and it's a little smaller/lighter than the Tesla. The FC-5000 looks nice if you want a full on tablet, but I bet it's heavy. The Tesla isn't light, but as long as I can get over it's trashy processor I'll be okay.

Not sure if any of that helped answer your question.
Forgot to say, my current Topcon robot is a PS-103. All in all it's a good gun. I just can't wait for the day that I can hang up total stations and use VRS for every job...even the ones in the summer time Appalachian jungle canopy. Keep dreaming, I guess...


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