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TC

Tom Curlee

Tue, Dec 20, 2016 6:28 AM

A couple of questions:
I've just started using LH 5.0 with my 2 GPSDO units (Thanks Mark!) - a Trimble UCCM and a Z3801A. Oddly, I'm very getting different survey altitude values. The Z3801A is around 81 M, which agrees within 1 or 2 meters with Google maps (not a perfect source, but close), but the UCCM is usually around 48M to 53M depending on which survey I want to believe. Both receivers are locked and both are fed off the same antenna through a splitter. I admit that the antenna placement is very poor - anything below 60 degrees elevation to the north is blocked (LH is great for antenna placement analysis). Anyone have any ideas?
A question on LH usage. When the UCCM is in the position hold mode, what happens when a precision survey is run? Looking at the .lla file shows that every position, including the final processed location, is the same as that shown as the position hold location on the main LH screen. Do you need to take the receiver out of the hold mode to run a precision survey? How? How is the position scatter plot used with a survey? I usually don't see any positions plotted, certainly not when running a precision survey. I think I saw data plotted when I did an internal survey.
Many thanks for any info. And thanks again to Mark and John for all the work.
Tom

A couple of questions: I've just started using LH 5.0 with my 2 GPSDO units (Thanks Mark!) - a Trimble UCCM and a Z3801A. Oddly, I'm very getting different survey altitude values. The Z3801A is around 81 M, which agrees within 1 or 2 meters with Google maps (not a perfect source, but close), but the UCCM is usually around 48M to 53M depending on which survey I want to believe. Both receivers are locked and both are fed off the same antenna through a splitter. I admit that the antenna placement is very poor - anything below 60 degrees elevation to the north is blocked (LH is great for antenna placement analysis). Anyone have any ideas? A question on LH usage. When the UCCM is in the position hold mode, what happens when a precision survey is run? Looking at the .lla file shows that every position, including the final processed location, is the same as that shown as the position hold location on the main LH screen. Do you need to take the receiver out of the hold mode to run a precision survey? How? How is the position scatter plot used with a survey? I usually don't see any positions plotted, certainly not when running a precision survey. I think I saw data plotted when I did an internal survey. Many thanks for any info. And thanks again to Mark and John for all the work. Tom

E

EB4APL

Tue, Dec 20, 2016 11:21 AM

Elevation differences between GPS receivers usually come from the
elevation reference used, i.e. from the ellipsoid or the geoid, even
from the geoid being used.

Regards,

Ignacio , EB4APL

El 20/12/2016 a las 7:28, Tom Curlee escribió:

A couple of questions:
I've just started using LH 5.0 with my 2 GPSDO units (Thanks Mark!) - a Trimble UCCM and a Z3801A. Oddly, I'm very getting different survey altitude values. The Z3801A is around 81 M, which agrees within 1 or 2 meters with Google maps (not a perfect source, but close), but the UCCM is usually around 48M to 53M depending on which survey I want to believe. Both receivers are locked and both are fed off the same antenna through a splitter. I admit that the antenna placement is very poor - anything below 60 degrees elevation to the north is blocked (LH is great for antenna placement analysis). Anyone have any ideas?
A question on LH usage. When the UCCM is in the position hold mode, what happens when a precision survey is run? Looking at the .lla file shows that every position, including the final processed location, is the same as that shown as the position hold location on the main LH screen. Do you need to take the receiver out of the hold mode to run a precision survey? How? How is the position scatter plot used with a survey? I usually don't see any positions plotted, certainly not when running a precision survey. I think I saw data plotted when I did an internal survey.
Many thanks for any info. And thanks again to Mark and John for all the work.
Tom

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Elevation differences between GPS receivers usually come from the elevation reference used, i.e. from the ellipsoid or the geoid, even from the geoid being used. Regards, Ignacio , EB4APL El 20/12/2016 a las 7:28, Tom Curlee escribió: > A couple of questions: > I've just started using LH 5.0 with my 2 GPSDO units (Thanks Mark!) - a Trimble UCCM and a Z3801A. Oddly, I'm very getting different survey altitude values. The Z3801A is around 81 M, which agrees within 1 or 2 meters with Google maps (not a perfect source, but close), but the UCCM is usually around 48M to 53M depending on which survey I want to believe. Both receivers are locked and both are fed off the same antenna through a splitter. I admit that the antenna placement is very poor - anything below 60 degrees elevation to the north is blocked (LH is great for antenna placement analysis). Anyone have any ideas? > A question on LH usage. When the UCCM is in the position hold mode, what happens when a precision survey is run? Looking at the .lla file shows that every position, including the final processed location, is the same as that shown as the position hold location on the main LH screen. Do you need to take the receiver out of the hold mode to run a precision survey? How? How is the position scatter plot used with a survey? I usually don't see any positions plotted, certainly not when running a precision survey. I think I saw data plotted when I did an internal survey. > Many thanks for any info. And thanks again to Mark and John for all the work. > Tom > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

OP

Ole Petter Ronningen

Tue, Dec 20, 2016 12:24 PM

Possibly the z3801 reports heigh as MSL, whereas the UCCM use some other
reference frame.

Ole

On Tue, Dec 20, 2016 at 7:28 AM, Tom Curlee tcurlee@sbcglobal.net wrote:

A couple of questions:
I've just started using LH 5.0 with my 2 GPSDO units (Thanks Mark!) - a
Trimble UCCM and a Z3801A. Oddly, I'm very getting different survey
altitude values. The Z3801A is around 81 M, which agrees within 1 or 2
meters with Google maps (not a perfect source, but close), but the UCCM is
usually around 48M to 53M depending on which survey I want to believe.
Both receivers are locked and both are fed off the same antenna through a
splitter. I admit that the antenna placement is very poor - anything below
60 degrees elevation to the north is blocked (LH is great for antenna
placement analysis). Anyone have any ideas?
A question on LH usage. When the UCCM is in the position hold mode, what
happens when a precision survey is run? Looking at the .lla file shows
that every position, including the final processed location, is the same
as that shown as the position hold location on the main LH screen. Do you
need to take the receiver out of the hold mode to run a precision survey?
How? How is the position scatter plot used with a survey? I usually don't
see any positions plotted, certainly not when running a precision survey.
I think I saw data plotted when I did an internal survey.
Many thanks for any info. And thanks again to Mark and John for all the
work.
Tom

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.

Possibly the z3801 reports heigh as MSL, whereas the UCCM use some other reference frame. Ole On Tue, Dec 20, 2016 at 7:28 AM, Tom Curlee <tcurlee@sbcglobal.net> wrote: > A couple of questions: > I've just started using LH 5.0 with my 2 GPSDO units (Thanks Mark!) - a > Trimble UCCM and a Z3801A. Oddly, I'm very getting different survey > altitude values. The Z3801A is around 81 M, which agrees within 1 or 2 > meters with Google maps (not a perfect source, but close), but the UCCM is > usually around 48M to 53M depending on which survey I want to believe. > Both receivers are locked and both are fed off the same antenna through a > splitter. I admit that the antenna placement is very poor - anything below > 60 degrees elevation to the north is blocked (LH is great for antenna > placement analysis). Anyone have any ideas? > A question on LH usage. When the UCCM is in the position hold mode, what > happens when a precision survey is run? Looking at the .lla file shows > that every position, including the final processed location, is the same > as that shown as the position hold location on the main LH screen. Do you > need to take the receiver out of the hold mode to run a precision survey? > How? How is the position scatter plot used with a survey? I usually don't > see any positions plotted, certainly not when running a precision survey. > I think I saw data plotted when I did an internal survey. > Many thanks for any info. And thanks again to Mark and John for all the > work. > Tom > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. >

BC

Bob Camp

Tue, Dec 20, 2016 7:54 PM

Hi

The simple answer is that you want to do the survey on the specific GPSDO you will be using.
You feed the results of that survey back into the GPSDO as it’s fixed location. There are a number
of subtle issues that can creep into the GPS module’s location estimate. Whatever the issues are,
they are also (hopefully) built into the survey data the GPS reports. This is also another reason to
run very long surveys (many days). That way you include as much of the weirdness into the survey
as you can.

Would it be better to have a perfect GPS that is always correct in all regards? Sure it would be. Since
these devices are done on a budget that is probably not going to happen. A GPS module that originally
sold for < $50 is not going to compete with a $4,000 survey receiver (which also may have anomalies).

Bob

On Dec 20, 2016, at 1:28 AM, Tom Curlee tcurlee@sbcglobal.net wrote:

A couple of questions:
I've just started using LH 5.0 with my 2 GPSDO units (Thanks Mark!) - a Trimble UCCM and a Z3801A. Oddly, I'm very getting different survey altitude values. The Z3801A is around 81 M, which agrees within 1 or 2 meters with Google maps (not a perfect source, but close), but the UCCM is usually around 48M to 53M depending on which survey I want to believe. Both receivers are locked and both are fed off the same antenna through a splitter. I admit that the antenna placement is very poor - anything below 60 degrees elevation to the north is blocked (LH is great for antenna placement analysis). Anyone have any ideas?
A question on LH usage. When the UCCM is in the position hold mode, what happens when a precision survey is run? Looking at the .lla file shows that every position, including the final processed location, is the same as that shown as the position hold location on the main LH screen. Do you need to take the receiver out of the hold mode to run a precision survey? How? How is the position scatter plot used with a survey? I usually don't see any positions plotted, certainly not when running a precision survey. I think I saw data plotted when I did an internal survey.
Many thanks for any info. And thanks again to Mark and John for all the work.
Tom

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Hi The simple answer is that you want to do the survey on the specific GPSDO you will be using. You feed the results of that survey back into the GPSDO as it’s fixed location. There are a number of subtle issues that can creep into the GPS module’s location estimate. Whatever the issues are, they are also (hopefully) built into the survey data the GPS reports. This is also another reason to run very long surveys (many days). That way you include as much of the weirdness into the survey as you can. Would it be better to have a perfect GPS that is always correct in all regards? Sure it would be. Since these devices are done on a budget that is probably not going to happen. A GPS module that originally sold for < $50 is not going to compete with a $4,000 survey receiver (which also may have anomalies). Bob > On Dec 20, 2016, at 1:28 AM, Tom Curlee <tcurlee@sbcglobal.net> wrote: > > A couple of questions: > I've just started using LH 5.0 with my 2 GPSDO units (Thanks Mark!) - a Trimble UCCM and a Z3801A. Oddly, I'm very getting different survey altitude values. The Z3801A is around 81 M, which agrees within 1 or 2 meters with Google maps (not a perfect source, but close), but the UCCM is usually around 48M to 53M depending on which survey I want to believe. Both receivers are locked and both are fed off the same antenna through a splitter. I admit that the antenna placement is very poor - anything below 60 degrees elevation to the north is blocked (LH is great for antenna placement analysis). Anyone have any ideas? > A question on LH usage. When the UCCM is in the position hold mode, what happens when a precision survey is run? Looking at the .lla file shows that every position, including the final processed location, is the same as that shown as the position hold location on the main LH screen. Do you need to take the receiver out of the hold mode to run a precision survey? How? How is the position scatter plot used with a survey? I usually don't see any positions plotted, certainly not when running a precision survey. I think I saw data plotted when I did an internal survey. > Many thanks for any info. And thanks again to Mark and John for all the work. > Tom > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

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Trimble UCCM survey results