Just curious

[Nate The Surveyor]

What are the parameters of RTK GPS, @ 5hz? What is it doing?
What are the parameters of PPS, GPS @ 1 Hz? What is it doing?

I am imagining that 5 hz RTK is processing, and sending more data, base to rover, than 1 hz stored.

I am imagining that 1 hz stored, means that it can pile up ALL the differential data, and "Lump sum" it at the computer, that is "differencing" them.

So... In theory, if the base were storing at the 5 hz rate, (humongous files!) and so were the rover, then the solution could be maybe a few percentage points stronger. Because, more data to pick through, yields a larger sampling, to analyze. (also much slower)
And, the 5hz mode, in RTK is in actuality transferring a huge data stream, base to rover. IF this were allowed to "Accumulate", then potentially, (and data stream, base to rover was un interrupted) then potentially, the RTK solution could be more robust?

I have been guilty, as a kid, of taking things apart, that I knew nothing about, just to "See how they worked".
I was VERY disappointed, when I took my first transistor radio apart.... Those "People inside, singing, must have run off very fast!". (funny)

Just curious. It's OBVIOUS that 5 hz is superior. I may be meddling deeper than my education. (like I have never done that!)


Nate

 

[Matt Johnson]

Positions measured by GNSS receivers contain errors caused by inaccuracies in the satellite and receiver clocks, the satellite orbits and by the ionosphere and troposphere. When a base station is used, these errors are nearly identical to both the rover and base station receivers when the baseline distance is short. By removing these common errors through RTK double difference processing, centimeter level accurate vectors can be calculated between the base and the rover.

When the double difference ambiguities are estimated as real numbers, a float solution is obtained. When the ambiguities can be constrained to fixed integers, a fixed solution is achieved. Determining the correct integer ambiguities of a fixed solution is a statistical process and the probability of fixed solutions providing inaccurate position solutions increases in poor environments.

At 5Hz, the base transmits corrections 5 times a second and there are 5 times as many data points available for processing as compared to 1 Hz. With more data points available, a fixed solution can be solved for faster. The time required to acquire a fix is inversely proportional to the rate of the corrections. 5Hz doesn't give an RTK solution a higher degree of confidence, it just makes it faster to obtain.

 

[Nate The Surveyor]

OK, so the 5hz rate is not going to improve accuracy, if used to solve the PPS, solution.

 

[Matt Johnson]

5hz data could help the PPS if the recording period is not long enough to get a fixed solution but other than that it probably won't help much.

 

[Nate The Surveyor]

Ok, so I conclude that although 5 hz is great, for getting a strong fix fast... It is not a substitute for time, which is the mechanism, for developing high accuracy coords.
So the 5hz relates to fast verification. And time relates to high accuracy.
So, I'd derive that... For a high certainty shot, leave the confidence counter high. But time can be lower.
For a shot that's important, like a ctrl station, to move the base on, give it more time. Last wk, I did 2, 200 second observations, on an extra ctrl station. The 2 points were in the clear, and wound up less than 0.01' apart.
Thoughts? These are my own "educated assumptions".

 

[Adam]

I think you are on track, Nate.