[time-nuts] Lady Heather V6.0 and RINEX files...

[Michael Baker]

Time Nutters--

There are several cosmetic tweaks.

A major new feature is the ability to write RINEX files for receivers that can output satellite RAW observation data. RINEX files can be processed to produce very accurate positions (typically 150-250mm for L1 only receivers, 10mm for L1/L2 receivers). The recommended online processor is CSRS-PPP from Natural Resources of Canada (NARCAN)... they seem to be the only service that supports L1 only data.
************

In layman's terms, what does this mean with regard to being
able to set an *AFFORDABLE* GPS RX out in the field and use it
to do site surveys and process the recorded RINEX data later to
establish the geo-position of each of the sites within a precision
of +/- a few centimeters? I presume this may not be a simple as
setting up my Trimble Thunderbolt and Lady Heather V6.0 in the
field and gathering RINEX files for a few minutes....??

Mike Baker
Micanopy, FL
*************


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[Mark Sims]

Actually it is that simple. The relevant RINEX commands are in the new "M" (mesurement) keyboard menu. The MW command is used to write the file. MR is used to set the measurement rate (defaiult 1 second). The other commands mostly provide various info that can be added to the RINEX file (marker name, number, antenna type, number, etc).

The Trimble and Furuno GT87xx receivers are not the best ones for precise positioning since they only have pseudorange data to work with. The Ublox, NVS, and Venus RTK receivers also output carrier phase data. The Ashtech Z12 is the best since it is L1/L2 with carrier phase data..

As far as "a few minutes"... you need at least a couple of hours of data. 12-24 hours can improve the results by 50+%. I am getting reported error ellipses in the 150mm range (< 10mm for the Z12)

---------------

Post by Michael Baker
I presume this may not be a simple as

setting up my Trimble Thunderbolt and Lady Heather V6.0 in the
field and gathering RINEX files for a few minutes....??
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[Bob kb8tq]

Hi

Post by Michael Baker
Time Nutters--

There are several cosmetic tweaks.

A major new feature is the ability to write RINEX files for receivers that can output satellite RAW observation data. RINEX files can be processed to produce very accurate positions (typically 150-250mm for L1 only receivers, 10mm for L1/L2 receivers). The recommended online processor is CSRS-PPP from Natural Resources of Canada (NARCAN)... they seem to be the only service that supports L1 only data.
************
In layman's terms, what does this mean with regard to being
able to set an *AFFORDABLE* GPS RX out in the field and use it
to do site surveys and process the recorded RINEX data later to
establish the geo-position of each of the sites within a precision
of +/- a few centimeters? I presume this may not be a simple as
setting up my Trimble Thunderbolt and Lady Heather V6.0 in the
field and gathering RINEX files for a few minutes....??

Even with L1/L2 survey gear, “a few centimeters” is a bit more than a
few minutes of data. So far, 24 hour records with L1 gear have given
meter level precision.

Bob

Post by Michael Baker
Mike Baker
Micanopy, FL
*************
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[Michael Wouters]

I've done some experiments with the NV08C and NEO8MT recently. Both of
these receivers report L1 carrier phase. Using the CSRS-PPP service, I
don't get quite as good results as Mark. The errors are more like 0.5 m
(95% confidence interval) in X,Y,Z. However, there is a systematic error
too of about 0.5 m, mostly in Z. My guess is that it's because I'm in
Australia and CSRS don't have as much data as they do in North America for
estimating ionosphere. There is a dense local CORS network but access is
not free.

The other thing I tried was using the receivers in base-rover configuration
with various CORS stations out to 100 km and this worked very well. The
positions I got using RTKLIB were good to 5 cm or so. I know exactly where
the antenna is because it's an IGS station. The NV08 worked best. Antenna
quality was important too. When I moved from the choke ring to a 'cheap and
cheerful' there was a marked decrease in the quality of the data - the
RTKLIB positioning solution would drop in and out of lock. Nonetheless,
useable data could be obtained. Other things I have read suggest that this
could be improved with more sophisticated software.

Cheers
Michael

Post by Michael Baker
Hi

Post by Michael Baker
Time Nutters--

There are several cosmetic tweaks.

A major new feature is the ability to write RINEX files for receivers

that can output satellite RAW observation data. RINEX files can be
processed to produce very accurate positions (typically 150-250mm for L1
only receivers, 10mm for L1/L2 receivers). The recommended online
processor is CSRS-PPP from Natural Resources of Canada (NARCAN)... they
seem to be the only service that supports L1 only data.

Post by Michael Baker
************
In layman's terms, what does this mean with regard to being
able to set an *AFFORDABLE* GPS RX out in the field and use it
to do site surveys and process the recorded RINEX data later to
establish the geo-position of each of the sites within a precision
of +/- a few centimeters? I presume this may not be a simple as
setting up my Trimble Thunderbolt and Lady Heather V6.0 in the
field and gathering RINEX files for a few minutes....??

Even with L1/L2 survey gear, “a few centimeters” is a bit more than a
few minutes of data. So far, 24 hour records with L1 gear have given
meter level precision.
Bob

Post by Michael Baker
Mike Baker
Micanopy, FL
*************
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[Mark Sims]

Yes, the altitude error estimates are generally around twice the lat/lon values.

I'm currently playing with taking the same 16 hour/1 sec interval data set (from a Trimble Acutime GG receiver) and decimating it to 5/10/30 second intervals and also to 2/4/8/16 hour lengths and seeing how the results change.
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