Does anyone know, if a PM2, in S&G with 6 sats on the kinematic-indicator, but 8, or even 9 sats pegged on the sat-view indicator, will indicate a lock-loss, if 2 of the sats shown on the kinematic screen are blocked?

I did some xperimentation with this today. I began on a clear hill-top(5-6 sats on the S&G indicator, with 8-9 on the sat-view(pegged). Walked down a hill, under a large tree with more "blockage", to the south and never got a peep or warning.

The base was in open view.

After going under the tree, my GPS positions were off by almost 2 feet . . .1.78 and 1.89(spot on before leaving the hill-top).

It will show the alarm when it drops down to five satellites.

It really only needs four, but it is conservatively set to five.

Remember, the system doesn't know whether you have the COMMON satellites you really need, you only know that after you process your data.

John, are you saying that you got "fixed" post processed solutions that were actually off by about two feet after walking by a tree?

How long were your observation times after walking by the tree and how many observations were bad after that?

Were you using GNSS or AS 2.x post processing?

The number of satellites that are shown collecting data on the bar screen of the PM2 does not always correspond with the number of satellites on the main screen. Sometimes the main screen also indicates something different than what you see at post processing time.

You can get good S&G data with six satellites but if the PDOPs are jumping around over 4 it becomes questionable.

When the number of satellites are good but you you get a loss of lock alarm due to walking under temporary obstructions I've learned that it does not always mean the next S&G observations are going to be problems at post processing time.

But I think this has now been explained... the warning buzzer is set conservatively... you can sometimes get good results with brief shortages of satelites down to 5 as long as the next observations come right back up to good coverage- say 7-8 sats or more

And of course the control GPS unit is always nearby collecting clean data from all 8 satellites.

As I said, the base was in the open. It was actually on a nob with full coverage.

If any unit would've been affected by any sat-losses or blockage, it had to be the rover, which I purposely took into a somewhat questionable area.

See Data Cleaning Part 2.

ftp://ftp.magellangps.com

Land Survey --> EOL --> Ashtech Solutions --> Application Notes

Losing the solution is possible even if you never lose lock. Data Cleaning Part 2 illustrates how this can happen.