Precision-geo-inc, post: 333407, member: 9801 wrote: All their features like SmartCheck, multipath mitigation, etc. are things that the squints in Switzerland developed and are unique only to Leica equipment.
I'm a big fan of Leica equipment and I worked for Leica for six years, but it's comical that they claim they're the only ones doing background checking of the ambiguities. They used to say (back in the System 500 days) that Trimble fixed the ambiguities and then held that solution with no background checking, which was not the case.
The striking difference between Leica and Trimble was that at Leica meetings they spent a significant amount of time talking about how Trimble did things and why Leica was better. At Trimble meetings they only talked about what Trimble was doing. I guess when you have (at the time, anyhow) 70% of the market share you're not worried about what the other 30% are up to.
I was always taught "Accurate GPS shots under canopy." doesn't exist. You can have one or the other but not both. I know one surveyor who had a Trimble and Lecia dealer give demos on the same points around his office with several being under canopy, which he tied in with a total station. One brand gave an answer for the points under the canopy and the other wouldn't. He bought the one that wouldn't.
Lamon Miller, post: 333924, member: 553 wrote: One brand gave an answer for the points under the canopy and the other wouldn't. He bought the one that wouldn't.
With some business models, I would support this decision 100%. If you are sending out crews that cannot be trusted to make the necessary checks to ensure that a differential GPS position (be it static or RTK) is correct, best to not give them the ability to abuse a system that fixes in poor environments. However, if you, or those under your responsible charge can be trusted to make the necessary checks, then I think it's wise to consider a system that will provide fixed solutions in those challenging places.
I did a review of a system several years ago. It accurately resolved ambiguities (fixed) in amazing places, particularly for the time. However, it did give some bad fixes in marginal places. Before I submitted the article, the manufacturer tightened up the tolerances required to report a "fixed" solution and then had me re-evaluate. In my re-evaluation the receiver still performed well, but didn't give fixes in the places I was able to fix previously. Of course, if a receiver is constantly giving bad fixes, then the statistical tolerances are probably too loose. I believe an occasional bad fix, that is discoverable, would suggest the receiver is more likely to be productive in more places. It just requires an operator that is paying attention and doing his part.
Like many politicians, my position on this point has evolved over the years and is specific to my workflow. I once believed that if a system gave any bad fixes, it was a failure on the part of the receiver. Now, I believe that if I can get to a remote location, in a poor environment and prove through preponderance of multiple fixes that a position is good (even if I have to weed through some bad fixes), that this is preferable in many instances to the alternatives. I have to be willing to accept the occasional bad to get the good. As long as I have a filter to recognize the difference, I can be more productive this way. If I weren't checking, I would want a much more restrictive indication of a fix. Thus far, every receiver I have ever used, I was able to trick into providing a bad fix, except for one. Unfortunately that one has an asterisk by it because I didn't have the time to really push it, although it did do very well in my limited test. My point being, it's possible to fool any of them, in my opinion and that's not necessarily a bad thing.
Lamon Miller, post: 333924, member: 553 wrote: I know one surveyor who had a Trimble and Lecia dealer give demos on the same points around his office with several being under canopy, which he tied in with a total station. One brand gave an answer for the points under the canopy and the other wouldn't. He bought the one that wouldn't.
@ Lamon - Yeah I know that guy too; I was the salesman that lost that deal. He was definitely not a fan of the shots under canopy, but I had some other problems that probably had at least as much to do with it - I had some shots out in the wide open that were off a good bit. The only thing I could even begin to speculate on was that there's a big radio tower of some kind right by his office, I thought at the time that I might have been getting interfered with.
I think the dealer that won that one may have sweetened the pot by putting a free reference station on his office, but I'm not sure about that... I didn't dwell on the losses, you can't win 'em all.
What about once the leaves fall off? Any better results?
"What about once the leaves fall off? Any better results?"
Somewhat. But that doesn't equate to just patrolling around all winter getting trouble free positions in the woods. The bare branches will still give you multipath fits.
The best thing available today for better reception under canopy is more satellites. So you definitely want GLONASS capability.
The "new" L5 signal of GPS is much stronger than the others. So you want that in the long term. Trouble is that there aren't enough satellites up there broadcasting the L5 signal to make a real difference yet.
I'm close to buying but will it be worth the debt I'm going in for the potential profits I can make. It's not looking like it. I only get a handful of partly open jobs a year. It's all woods here.
The one I'm looking at has: GPS, GLONASS, BeiDou, Galileo & SBAS
Static, static, static with long session can give you decent results in deciduous canopy. But you will need at least three GNSS collecting static simultaneously. This way you can check the closure of the vectors between receivers. When working on large hardwood tracts we often use 6 receivers. Always keep one in wide open area at a fixed location all day and send only this to OPUS.
