1 vs 5 Hz Base Transmission Accuracy

[Jim Campi]

Gentlemen,

Is there a difference in pt accuracy under the following 3 conditions:

Condition 1 - 1 hz base trans
6 fixed engines
12 epochs
8 seconds

Condition 2 - 5 hz base transmission
6 fixed engines
12 epochs
1.6 seconds.

 

[Shawn Billings]

I do not believe that you would see any difference in accuracy in such a short span of time. It's possible that comparing 300 seconds at 1Hz might be better than 60 seconds at 5 Hz because multipath might be meaned out a bit better. But I think in short time frames (inside of a couple of minutes), that equal epoch counts will have equal precision, regardless of time. This is kind of gut feel and a little bit observation, but I don't have any hard data to share right now.

 

[Jim Campi]

Thanks Shawn.

I perform more topographic mapping than any other type of survey. Javad has been recommending the following settings for a "precise topo":

 Start with Start Button or Start When Tilted
 Stop After: 10 epochs
 Verify without V6 Reset
 Consistency Counter: 10
 Correct for Tilts: On*

I believe the sertings were discussed here and found in the current LS Users's Guide.

2 questions:
1. What do you think of these serrings for precise topo work; and
2. Do you see any reason to increase occupation time/epochs (or verificaion settings in general) when utilizing a 5 hz base update rate?

 

[Shawn Billings]

In my own work I would use those settings plus add the validate with two engines. That adds ten epochs after a reset. Every point gets one reset that way. At five hertz it cost about three seconds including time to fix and you end up with 20 epochs in about 6 or 7 seconds.

 

[Shawn Billings]

Regarding occupation times, Javad has made some changes recently that I would like to test a bit more, but in tests I ran earlier in the summer I found that 4 minute occupations were about 15% more precise (lower standard deviation in point clusters) than 20 second occupations. It seems that past 4 or five minutes there is a point of diminishing returns. In reality the returns are only about 15% improvement in precision. I still tend to occupy control for several minutes though. Mostly old habits.

This information is regarding points in the open. Things change under tree canopy. More time does mean out multipath errors to some degree.

 

[Jim Campi]

Thanks Shawn. I'm going to add a reset to my protocol.