ZED-F9P and PPP processing

[John Ackermann N8UR]

As noted in my other message, submitting ZED-F9P GPS-only data to NRCan
results in a consistently high (could be 20 to 50 percent) number of
rejected epochs, much greater than other receivers recorded using the
same antenna at the same time.  I've learned what causes this.

The ZED-F9P and -F9T receivers do not do the "old style" (military) L2
code.  They will only use the "civilian" L2C signal on the later
generation satellites (IIR-M and later).  On the older satellites
without L2C, they only do L1.

Most processing sites will reject dual-frequency observations that only
have data for a single channel, so NRCan throws out all the -F9*
observations from the older satellites.  That results in more epochs
without enough birds to do a solution.

Turning on GLONASS helps this situation because the added SVs mean that
more epochs can generate a solution.

So my next step is to set up F9P and F9T with one tracking only GPS, and
the other both GPS and GLONASS, to compare results.

John