Fungus,
Your image is of an "inverted PPS".
On timing-oriented modules and boards there is often (always?) a jumper or switch which allows the user to select "inverted 1PPS" and/ or other kinds of time pulses. Then the pin may default to being usually in a high condition and will momentarily go low at the beginning of each second. That is quite common.
But the norm is the opposite with my non-timing equipment.
The change, nomatter what direction it is in, is hard to see unless you trigger on the leading or falling edge as is appropriate. Because its so short. Also, it wont show up for some time when a GPS is started cold because it takes a minimum of around 13 minutes for the GPS to acquire ephemeris information, usually longer.
Assuming access to a good quality active GPS antenna with a good sky view, I would expect to see a fix within half an hour or less, but almost never less than around 13 minutes unless the ephemeris is already in memory (AGPS, etc).
The following is from a datasheet for one module I own and this is the non-timing GPS norm.
"One-pulse-per-second (1PPS) time mark output, 3V LVTTL. The rising edge synchronized to UTC second when getting 3D position fix. The pulse duration is about 4msec at rate of 1 Hz" (actually, that is short, compared to most- most are longer- 10 usec might be more typical, not 4)
Ive never owned a timing specific GPS and my experience with GPS in the time measurement context is relatively recent (the last decade, basically).
But the main thing I wanted to say here is - they all are picky about when they will deliver the pulses. They need to be.
There have been many times that I have seen GPSs - especially indoors, and timing pulses, etc, suddenly spring to life after some long time. Usually right about when I was going to give up on it.
You can look at the NMEA data stream and track the process by selecting the appropriate sentences. Some indicate acquisition of SVs, and signal strength and quality, some don't.