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Base/Rover – what’s being transmitted?
My question is mostly a Trimble one, but may be applicable to other brands as well.
When working with a base/rover connected by radio, is there information other than that of the 4 constellations being sent to the rover by the base? Specifically, if a person is using a lower end receiver for a base, say an R8m4, and a higher end R12i for the Rover; is some functionality lost, or does all the magic happen on the Rover end?
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18 Replies
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The DC at the rover is doing the calculations. If the rover collects more satellite data than the base, the extra rover data isn’t used to refine the position of the rover.
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Not necessarily so. With the exception of the RX1230, every Leica unit I have owned or used has done the calculations on the receiver side. If I have it set to base/radio, my GS18 has a fixed location with or without the data collector. My rail geometry trolley sucks the NMEA stream out of the head, no DC in the equation.
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But it is still the rover receiver were the action is, right?
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Both receivers are doing lots of calculations. But the OP’s question made me think of Base/Rover RTK where the data is reduced real time at the rover, Javad has a built in DC, but it’s still calculating the solutions with the DC. A base/rover can operate without a DC, simply collect at the Rover and later post process the data.
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“The DC at the rover is doing the calculations”
This is not my understanding. The messages from the satellites and the messages from the base are being processed in the rover itself. The resulting position, accuracy assessment, etc are then sent to the DC. If you are using a network for your base, then it is probable that your DC is getting the base information and sending it to the rover.
Notice that for a lot of rovers, when you go “fixed” the rover head itself will produce a sound or flashing lights, etc.
As for using different base and rover configurations, certain quirky companies with dark green boxes encouraged this. I am not an expert, but I can tell you that from my experience, matching capabilities and configurations is the apex of RTK efficiency. YMMV on whatever other choices you may make. The OP’s situation should certainly work, but the ability to track and “see” all of the same constellations and vehicles is very useful. Only the satellites that are seen by both the rover and base are useful in the final solution, from what I understand.
I do acknowledge that I am on the edge of ignorance in these matters, so am open to “corrections from a based” knowledge source.
-All thoughts my own, except my typos and when I am wrong. -
Just to be clear, can you set accurate line points real time with only your receiver rover head?
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When you say the rover is doing all of the calculations do you mean up to the point of determining its current lat long position? Or do you mean that the rover also calculates the local coordinate position?
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This reply was modified 7 months, 2 weeks ago by lurker.
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This reply was modified 7 months, 2 weeks ago by
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This is not my understanding. The messages from the satellites and the messages from the base are being processed in the rover itself. The resulting position, accuracy assessment, etc are then sent to the DC. If you are using a network for your base, then it is probable that your DC is getting the base information and sending it to the rover.
Usually this is the case – that’s why those rovers cost $$$$. Dedicated processors with proprietary RTK engines are doing all the heavy lifting under the hood, with the data collector simply serving as an intermediary.
There are such things as Software-Defined Receivers (SDR), which utilize a cheaper, “dumb” antenna without those onboard chips, and perform all the actual signal processing and vector resolution in the data collector.
Trimble’s Catalyst is a good example of this – the antenna costs less than $500, but the software and subscription service is what will get you, because that’s where all the precise positioning happens – in a phone or tablet running the proprietary software to reduce those measurements down to survey-grade precision.
SDR is a really cool concept, but from I have read, the traditional dedicated rover method is still more efficient and reliable. I think that might change in the future.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman -
Mr. Moe said – “A base/rover can operate without a DC, simply collect at the Rover and later post process the data.”
The same base/rover can also operate in RTK mode without a DC. Take a look at the NMEA data strings that can be output by the rover receiver, those can be output without having a DC. They provide fix information as well as positions as accurate as anything you get by having a DC.
The DC certainly makes the information more usable, but the rover receiver is where the position problem (integer-abiguity solution, etc.) is solved.
GB
Edit – The preceding applies to Trimble – my knowledge of other products is nonexistent.
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This reply was modified 7 months, 2 weeks ago by Glenn Borkenhagen.
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This reply was modified 7 months, 2 weeks ago by
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“The DC certainly makes the information more usable”
So the information is there, but you can’t use it Real Time; kinda what I’ve been saying,,,,,,,,,I think.
What’s the point of thinking it’s RTK when the position has to be found after downloading the receiver files and processing them? Isn’t that simply PPK? We all know PPK is possible without a DC.
The contractor is asking you to give him an elevation at a stake as you’re both standing next to it, all you have is an R10 head picking up data, how do you find that elevation real time with just the head?
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Maybe I didn’t state my question clearly enough…
For this question, consider the Rover/DC as a single entity.
Say the rover unit is the top of the line sophisticated model.
Does it get faster or more accurate solutions if the base is a more sophisticated model – given that any base in question tracks the sMe four constellations??
Is there a benefit to having an R12 base vs an R8m4 with an R12 rover???
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MM sez: “What’s the point of thinking it’s RTK when the position has to be found
after downloading the receiver files and processing them?”Take a look at the following image lifted from a Trimble receiver manual showing the NMEA-183 string designated as GGA. It provides latitude, longitude, and elevation, along with other information, can easily be done without a DC. When field 6 is “4”, the position is RTK fixed. No need for downloading/ postprocessing; the receiver can produce the RTK position all by itself.
Granted, unless one is some sort of silicon-based lifeform it takes a device to see and use the information.
GB
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Well, it looks like all that will be integrated soon. No longer will there need to be a DC, all that data will be directedly bluetooth uploaded from the receiver into your brain.
Elon will have that brain direct interface ready soon. All the data can be processed with the brainchip.
No need for a TSC5.
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To answer the basic question, only satellites and signals both receivers are receiving can be used. So there are satellites and signals the R12i receives that the R8-4 cannot.
With R12i you will get faster initialization than R8-4 as a rover and tilted observations
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Does it get faster or more accurate solutions if the base is a more sophisticated model – given that any base in question tracks the sMe four constellations??
It’s not just constellations, but signals as well….but the answer is generally no.
If a “less sophisticated” base still tracks the same signals and constellations as a “more sophisticated” base….with the same rover and transmission protocol, all else being equal you will see the same results.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman -
Well maybe not set line, since the DC is still where the stakeout routines are completed. But when I use my GS16 and GS18 on our Amberg trolley, without a DC, the GS send fixed coordinates to the trolley’s brain via NMEA stream.
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For Trimble at least…the computations are being done at the rover, not the data collector. The data collector is receiving the processed data from the rover as positions and statistics, computing the average, etc.
I can connect my R10 directly to a another receiver running an NTrip caster over a cellular connection. The positions that can be output from the rover, for example via NMEA GGA, are RTK fixed solutions.
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It’s not Trimble (CMR, CMR+, CMRx), but this gives a good idea about what is (can be) transmitted:
https://www.use-snip.com/kb/article-categories/message-decoding/
use-snip.com
Helpful articles on decoding and viewing various RTCM messages with SNIP.
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