So, my local Trimble dealer tells me the R10 can't be configured to broadcast and receive 5HZ RTK.
I think he probably doesn't know what he's saying. Has anyone tried it? Figured it out? I will admit that it's not readily explained in any of their documentation.
Admittedly I'm not the brightest bulb in the box, but I fail to see how broadcasting at 5Hz provides any benefit when the satellites only transmit at 1Hz. Anything faster than 1Hz has to be interpolated whether it's at the base or the rover.
Lee D, post: 349013, member: 7971 wrote: Admittedly I'm not the brightest bulb in the box, but I fail to see how broadcasting at 5Hz provides any benefit when the satellites only transmit at 1Hz. Anything faster than 1Hz has to be interpolated whether it's at the base or the rover.
Are you saying that the "Chippers" on the satellites are only chipping at once per second?
I Recall that they are more like several hundred times per second.
What is the hz of a Satellite for GPS navigation?
N
The satellite carrier frequencies are around 1575 mhz
Navagation data is transmitted at 50 BPS
Lee D, post: 349013, member: 7971 wrote: Admittedly I'm not the brightest bulb in the box, but I fail to see how broadcasting at 5Hz provides any benefit when the satellites only transmit at 1Hz. Anything faster than 1Hz has to be interpolated whether it's at the base or the rover.
Lee,
I can assure you that there is no interpolation. The satellites to not broadcast a single message package. It is a constant stream of data.
Lee D, post: 349013, member: 7971 wrote: Admittedly I'm not the brightest bulb in the box, but I fail to see how broadcasting at 5Hz provides any benefit when the satellites only transmit at 1Hz. Anything faster than 1Hz has to be interpolated whether it's at the base or the rover.
There may not be any benefit, but I see even less benefit in not trying and poo pooing someone for doing so.
Just wanting to expirement. We as a group can argue until the cows come home (and I hope we do, it's good food for thought) about some things, but a lot of times the proof is in the doing.
It's been a while since I read it, but I seem to remember Van Sickle's book detailing that the information stream is near continuous.
Plumb Bill, post: 349038, member: 226 wrote: There may not be any benefit
The benefit is that it reduces the time to fix. With the Javad TRIUMPH-LS, I have found with 2 Hz corrections, the average time for 4 of the 6 engines to fix was reduced by 46 percent to 6.7 seconds compared to 12.5 seconds with 1 Hz corrections. With 5 Hz corrections it was reduced by 72 percent to 3.5 seconds. The benefit of this is that Javad's RTK Verification and Validation processes can be completed much faster. Javad's RTK Verification and Validation are processes of resetting the RTK engines at the beginning and end of observations to ensure the RTK engine initiations are correct.
Plumb Bill, post: 348977, member: 226 wrote: So, my local Trimble dealer tells me the R10 can't be configured to broadcast and receive 5HZ RTK.
That's probably correct. You see, there is NOTHING here to see. It does not do anything, UNTIL Trimble can do it, there will be nothing to see. When Trimble does it, THEN there will be something to see!
Ummm hmmm Seems I have heard that line before. Way back when Trimble could not do GLONASS. Trimble said the same thing. Until Trimble does it, it does not exist!
🙂
Nate
Actually, both Trimble and Leica built prototype GPS / GLONASS receivers in the '90s. The decision not to bring them to market was a conscious one driven, if I remember correctly, by the fact that the GLONASS constellation was failing and was not, at the time, being replenished. It was no coincidence that Trimble and Leica both introduced their GPS / GLONASS receivers within weeks (if not days) of each other, that was also driven by events.
Most likely your R10 can broadcast at 5hz (why do you want this?). However your communication between the Base and Rover probably cant.
With GPS/GLONASS it is very difficult to compress a message into 1 second intervals, much less 5hz.
For example a Pacific Crest Radio can only broadcast at 1hz.
"High Over-the-Air Link Rate
19,200 bps (both GMSK and 4FSK)
Supports 1Hz RTK corrections for
multi-GNSS receivers"
http://pacificcrest.com/library/DS_ADL_VantagePro.pdf
As Eric said, I doubt any radio link could handle it. An ntrip connection over cell maybe could. But the real question is why? I think latency would make it moot.
Positioning rates (not RTK transmit) are 1 hz, 2hz, 5 hz, 10 hz, and 20 hz.
John Hamilton, post: 349086, member: 640 wrote: As Eric said, I doubt any radio link could handle it. An ntrip connection over cell maybe could. But the real question is why? I think latency would make it moot.
Javad base stations with UHF (with 12.5 kHz channel spacing and D16QAM modulation) or spread spectrum radios can transmit 5 Hz GPS/GLONASS corrections. I explained the reasons why you would want to above, it reduced the time to fix.
5Hz has been discussed quite a bit in other threads. It's been determined that transmission rates much higher than 5Hz have been available for some time from various manufacturers based on spec sheets (including older Trimble receivers). It's not immediately clear how various manufacturers would use the 5Hz or more transmissions at the rover. Most (all?) have said there is no practical benefit to surveyors for high rate transmission. The way Javad uses the signals, it does make a demonstrable difference in Time to Fix (TTF). Whether other manufacturers' rovers would actually see a benefit is unclear. Whether other manufacturers' can disseminate data at a rate greater than 1Hz seems clear based on Gavin's posts lately as well as private messages I've had with a knowledgeable vendor. Even if the R10 broadcast at 5Hz, I don't know, nor would I speculate, as to whether it would improve performance of an R10 rover.
Even though it was poo-pooed a bit that Javad advertised 5Hz as a new feature worthy of comment, it seems that transmission of 5Hz may need to include an asterisk:
*Just because the base can transmit 5Hz doesn't necessarily indicate that performance is improved at the rover with 5Hz.
Whether performance improves or not with various new and legacy receivers is a question for others to answer.
I need to get the new addition of Van Sickle's book, everything I've found on line just confuses the issue. I'm basing my 1Hz satellite transmission rate comment primarily on the fact of that's what I was taught, which doesn't mean it's correct. We were always told that anything faster than 1Hz was predictive interpolation.
We used to set up spread spectrum networks that operated at 128K baud, they'd be able to handle it, but there's no way a Trimble TDL (Pac Crest ADL) could. As an R10 user I still believe that if there was a practical benefit to it they'd be doing it, especially on the construction / machine control side. Time to fix is a non - issue with the R10 with Trimble Access, it's never more than a few seconds unless you're someplace you probably shouldn't be with GPS.
Lee D, post: 349138, member: 7971 wrote: I need to get the new addition of Van Sickle's book, everything I've found on line just confuses the issue. I'm basing my 1Hz satellite transmission rate comment primarily on the fact of that's what I was taught, which doesn't mean it's correct. We were always told that anything faster than 1Hz was predictive interpolation.
Even if the data is interpolated, one would think you could interpolate the future position of an SV rather accurately over one second of travel.
I do a lot of continuous topo of road location. It doesn't have to be survey grade, but 5HZ broadcast rate would increase the quality of the position.
I also can rather easily imagine that, if you are in canopy, you could just get more shots at 5HZ. Sort of like if the satellites were blinking like strobe lights through the trees instead of just a blinking flashlight. That's a very simple analogy, but I can't help but think that if you streamed more correction data, that you could get more shots through the trees. I am not in any way implying that the data would be better, just that you would BE ABLE TO COLLECT the data with initialization where you previously couldn't.
When taking shots with an R10 in rapid mode, I could possibly get a topo shot, wait a minute, reset init and check the shot - all in less time than I got the topo shot with 1HZ, simply because the receiver is looking for SVs more often. They're still playing peek-a-boo, just doing it much, much faster.
As I said before, I'm not sure if there is any benefit at all - I just want to see for myself. This document details that the signals are broadcast at rather high frequencies:
http://www.gps.gov/technical/ps/2007-PPS-performance-standard.pdf
Another thing to consider, even if the SVs only "ping" their message once per second, if there are 24 overhead - due to iono and tropo delays - you would receive 24 different signals spread throughout one second.
This paper gives a more detailed report of the message structure:
