[teqc] +QC report

Lou Estey lou at unavco.org
Tue Aug 14 10:32:29 MDT 2018


hi Colleen,

MP12 and MP21 are what (in UNAVCO's qc history) used to be called MP1 and MP2, respectively.
MP12 is the rms of a linear combination of L1 pseudorange and phase with L2 phase, whereas MP2
is the rms of a linear combination of L2 pseudorange and phase with L1 phase.  (When there was
just signals on GPS on L1 and L2 the older designations were enough to disambiguate the two
possible combinations.)

For the equipment at most sites, MP12 is often smaller than MP21 by 10-30%, but one can
easily find situations where the reverse is the case.

If you are looking at a long enough time period of data, say, hours, I'd say that one should
see MP12 and MP21 having values of no more than a couple of meters -- as a general guideline.

But due to the design of the algorithm, there is a trade-off between multipath slips and the
rms values: as counts of detected multipath slips go up, the rms values go down.  (In the
limit of multipath slips at every epoch, the rms is zero.)

For 30- or 15-second sampling, I'd say that observations per slip should be something like
500 or higher, but there are certainly many cases where one can successfully process data where
the observations per slip value is lower.   If there were the same number of slips per
unit time in high rate data, then one might expect the observations per slip to go up
by the factor of increased sampling rate, i.e. for 20-Hz sampling one might expect an
observation per slip counts of 100000 - 200000 or even higher, but I somehow doubt you're
actually going to see that.  You'll just have to experiment and see how your processing
software does with different observation per slip values.

Personally, I don't put too much stock in actual MP12 or MP21 values for setting hard-and-fast
"good" vs. "bad" thresholds.  There are just too many exceptions.

The utility of multipath rms, to me, is in monitoring these values over time and looking for
significant degradations, i.e. multipath rms increases.

--lou

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Louis H. Estey, Ph.D.              office:  [+001] 303-381-7456
UNAVCO, 6350 Nautilus Drive           FAX:  [+001] 303-381-7451
Boulder, CO  80301-5554            e-mail:  lou  unavco.org

"If the universe is the answer, what is the question?"
                                                -- Leon Lederman
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

On 10-Aug-18 09:00 AM, Brooks, Colleen (GSFC-694.0)[SCIENCE SYSTEMS AND APPLICATIONS INC] wrote:
> Good Morning,
> 
> Im trying to find out some information about the QC report and what certain things mean. Ive read through teh interperting teqc's qc Mode 
> output, and found a lot of useful information.  However im still missing some information regarding MP12 and MP21.
> 
> first off the code that i used to create my filename.##S file is as follows (its a 20hz file):
>      teqc +qc -iod_jump 18000 -ion_jump 8 -mp_win 900 filename.##o
> 
> I am trying to determine the quality of the data we receive from the receiver based on some of the information from the S file.  Im looking 
> at the tables under "MP12 RMS summary" and "MP21 RMS summary". I understand the tables themselves, but my question is about what is MP12 and 
> MP21 and what is the difference between the two.  And also should one summary be valued more heavily over the other?
> 
> And a second question, how many cycle slips is ok to see on a receiver/satelleite before we should become concerned?
> 
> -- 
> Colleen Brooks
> SSAI - Science Systems and Applications Inc.
> NASA/GSFC - Goddard Space Flight Center
> LVIS (Land Vegetation Ice Sensor)
> Bldg 22 Rm C135A
> Phone 301-614-6505
> e-mail:Colleen.Brooks at nasa.gov



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