[teqc] Explain some symbols in plot file

[Lou Estey]

mimo wrote:

> Hi my name is Mike and Im a student at Slovak Technic University in 
> Bratislava. Im finishing UNI this summer and now Im doing on my 
> graduation theses .  I have done quality check. And in final report 
> graph there are three symbols –dn,+dn +10 I don’t know what they are? 
> Would you  be so kind and send me the explanation of these three symbols 
> by email?

Mike,

 From http://facility.unavco.org/software/teqc/tutorial.html#sec_21

For qc full runs, the "Obs" line is replaced by four lines, labeled "-dn", "+dn", "+XX", and "Pos". The "+XX" line is the one most like the 
qc lite "Obs" line; the XX is replaced by the elevation mask in degrees (rounded to the nearest degree) and indicates the maximum expected 
number of SVs that are above the elevation mask, according to the supplied ephemerides, again using a hexidecimal notation. The difference 
between the qc lite "Obs" line and the qc full "+XX" line is the difference between reality and theory: "Obs" shows what was seen, where 
"+XX" shows what could have been seen (above the elevation mask).

The discrepancy between reality and theory is recorded in the "-dn" and "+dn" lines, which are the SV tracking discrepancy counts, and 
record the two bounds of the discrepancy. They can be thought of as the "good new/bad news" to the number of SVs not tracked. The line "-dn" 
records the minimum discrepancy of all observation epochs for that time bin while the line "+dn" records the maximum discrepancy of all 
observation epochs for that time bin. The discrepancy count is also shown in hexidecimal notation, with (blank) for 0.

For the discrepancy lines to work correctly, the option -max_rx_SVs must be set correctly. This states the maximum number of SVs that are 
capable of being tracked by the receiver, and currently has a default value of 12. If a complete observation gap occurs with qc full, a 
group of c characters will be shown (c is hex for 12), at least on the "+dn" line, and if the gap is large enough, on the "-dn" line as well.

cheers,
--lou

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