RTPK Elevations vs Base Processed RTK Elevation from 6 Mile Baseline

Matt Johnson

Matt Johnson

Well-Known Member
5PLS
Like I said earlier in this topic, RPTK should always be better than RTK (assuming receivers are aligned to north) and I don’t understand why anyone would choose RTK over RTPK. I am still waiting for someone do the test so that we have the data needed to understand the issue here. J-Field has all the tools needed to this. The LS needs to be setup at least 6 miles from the base with both aligned to north. Then it should be set to auto repeat and allowed to collect points for 24 hours. After the points are collected the average coordinates and Survey Statistics for both the RTK and RPTK need need to be calculated and compared.
 
nusouthsc

nusouthsc

Active Member
Matt Johnson said:
Like I said earlier in this topic, RPTK should always be better than RTK (assuming receivers are aligned to north) and I don’t understand why anyone would choose RTK over RTPK. I am still waiting for someone do the test so that we have the data needed to understand the issue here. J-Field has all the tools needed to this. The LS needs to be setup at least 6 miles from the base with both aligned to north. Then it should be set to auto repeat and allowed to collect points for 24 hours. After the points are collected the average coordinates and Survey Statistics for both the RTK and RPTK need need to be calculated and compared.
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Matt,
There are a few reasons we need RTK vs RTPK. First, is the time aspect. If I have to wait 1 min for every shot on every job, that's terribly impractical. Second, and more importantly, is there are plenty of situations where we do not have RTPK. On tough shots there are times that RTPK fails and RTK has a good solution. In this situation, the shot is precise, just not accurate in comparison to RTPK. So its not practical to have some RTK and some RTPK when there is 0.20' separation. Especially on property corners.

In reference to the test, if you can give me clear criteria I will be more than willing to do it. What RTPK interval would you suggest?
 
Matt Johnson

Matt Johnson

Well-Known Member
5PLS
nusouthsc said:
If I have to wait 1 min for every shot on every job, that's terribly impractical
Click to expand...
RTPK sessions can be set to durations as low 10 seconds.

nusouthsc said:
Second, and more importantly, is there are plenty of situations where we do not have RTPK. On tough shots there are times that RTPK fails and RTK has a good solution.
Click to expand...
When this happens are you also trying to process the data from the Points screen? Processing from the Points screen works better than processing the data while it is being collected and can provide a solution when you don't get one while processing live.

Surveying with long baselines and under tree canopy is not ideal and does not work well. If you are working under tree canopy you should set up a local base with a short baseline.

nusouthsc said:
In this situation, the shot is precise, just not accurate in comparison to RTPK.
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How do you know it is precise? To prove it is precise, you would need to take many observation spread across a long period of time (to allow the satellite geometry to change).

nusouthsc said:
In reference to the test, if you can give me clear criteria I will be more than willing to do it. What RTPK interval would you suggest?
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I would start with an interval of 1 minute and min RTPK Verification Level of 3. Have it collect points on Auto Repeat for 12 hours or 24 hours if you can connect an external power supply. Both the base and rover need to be aligned to north.
 
nusouthsc

nusouthsc

Active Member
Matt Johnson said:
RTPK sessions can be set to durations as low 10 seconds.


When this happens are you also trying to process the data from the Points screen? Processing from the Points screen works better than processing the data while it is being collected and can provide a solution when you don't get one while processing live.

Surveying with long baselines and under tree canopy is not ideal and does not work well. If you are working under tree canopy you should set up a local base with a short baseline.


How do you know it is precise? To prove it is precise, you would need to take many observation spread across a long period of time (to allow the satellite geometry to change).


I would start with an interval of 1 minute and min RTPK Verification Level of 3. Have it collect points on Auto Repeat for 12 hours or 24 hours if you can connect an external power supply. Both the base and rover need to be aligned to north.
Click to expand...
Matt,
Thanks for the input. I will certainly try to get this test underway as time allows. Just to be clear, for the LS to be oriented to north, the bearing on the interface needs to read South, correct? How does the T-3 need to be oriented to be north?
 
Sdrake14

Sdrake14

Active Member
This is a great thread guys! I have used my permanent base trusting RTPK up to 25 miles away, with comparisons to RTN (single baseline) within 0.10'.
Out here in the wild west that is splitting hairs on fly's rump. A lot of the surveys I retrace, sometimes, you are lucky to find the last guy was within 5 or 10 feet.
I was so glad that I had RTPK on that day, any other brand would have given me a big fat zero. I am not getting spoiled here though am I. Let's see the new limits of closure in the BLM Manual of survey instructions is 1 part in 1810. If I did a section breakdown out there 33 miles away and closed it with 0.35' error in the 4 mile perimeter, that is over 1 in 60,000. Am I going to whine about that? And that is if I was using RTK (if I could), but with a smidge of patience and RTPK, or Lord forbid PPK, I would easily have 1 in 200,000.

Never the less, this is great stuff and I want to test more.

Matt I am using my old LS as a base with an external GrAnt-G3T, how do I orient this antenna, or does it matter?
Thanks,
 
Tom Bushelman

Tom Bushelman

Member
both the LS and T3 the side with the buttons should be to the north.

I would not have guessed that. I figured me facing north, the LS reading north would have been oriented north. I've been backwards all along. Great thread.
 
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