GPS Units are typically limited to controlled airspace (60kfeet, 18km), and 1000 knots. These are commonly known as the COCOM limits. For anything outside of that, you will probably have to go for a higher-end GPS unit and possibly some additional paperwork.
I believe that the uBlox module that is on that board implements the COCOM limits correctly. In the uBlox G5010 datasheet, it gives the operational limits as 972 knots and 50km.
The DoD specification (I believe) says that a GPS unit should not operate above 60kfeet and 1000 or knots, but most of the manufacturers don't actually implement it this way. The commonly cited list of high-altitude capable GPS receivers is here.
Some other companies produce GPS units to spec: most notably Inventek.
I think Majenko's answer misses the mark a bit.
In order to get a rapid first fix, a GPS receiver needs to figure out quickly which satellites are in view, and their approximate Doppler shifts. In order to accomplish this, it needs two pieces of information: It needs to know roughly where in the world it is, and it needs to know roughly where the satellites are as well.
A-GPS refers to the former: by some means other than GPS, the receiver gets an approximate idea of where it is located. There are a number of ways of doing this; some WiFi access points broadcast their own geographic coordinates, which gives a pretty good idea of the receiver's loocation, since the coverage area of any particuar access point is fairly limited. Somewhat looser precision is available from cell towers, since their "footprint" is generally larger.
CGEE and SGEE are two methods of getting the second piece of data, the "ephemeris", which is a bunch of numbers that describe the orbits of all of the satellites and where they are currently located in those orbits. Without this information, the receiver must do a "blind search" until it finds at least one satellite, and then wait until that satellite broadcasts the ephemeris data for the rest of the constellation. Note that finding a satellite also helps narrow down the receiver's own position, since it must be somewhere within the "ground footprint" of that particular satellite, along an arc defined by the particular Doppler shift found.
CGEE basically means that the receiver extrapolates forward in time from information it had when it was last operating. Obviously, if the receiver is off for a long time, this information will become stale and relatively useless.
SGEE means that it gets current ephemeris information from an exernal server of some sort. Obviously, this requires that the receiver must have regular access to a network connection of some sort, which is readily achieved when it is embedded in a cell phone, for example.
Best Answer
PPS is not a fundamental function of GPS receivers. It is a axillary function that a GPS receiver can provide from it's internal timing systems that are used for actually measuring GPS position.
However, in many contexts, having a very precise local timestamp is highly beneficial. It is these applications where the PPS output is helpful.
Take a example where you have two sensor systems, perhaps a mile or two apart. They're going to have separate local clock oscillators, which will have different drift rates. The PPS signal, referenced to the GPS timestamp, is extremely useful for providing a way to accurately determine timing between the two systems. The GPS system compensates for the transmission time between each receiver and the GPS sattelite, so the PPS signals can be said to occur "simultaneously" to a considerable degree of precision, sometimes greater then the actual time-of-light transit between their positions!
For example, the LEA-6T timing GPS has a RMS time-pulse (e.g. PPS) output accuracy of 30 nanoseconds. Critically, that timing accuracy is position invariant compared to a theoretical global GPS time-base.
Note that this has fun effects like making the effects of the theory of relativity important to measurements. Light travels ~11.8" per nanosecond, but the GPS PPS output has a functionally infinite propagation speed, as all PPS pins theoretically would go high within the error band (~30 nanoseconds), invariant of their physical distance.
This works because the PPS output is not driven by an external pulse, but rather an internal clock that is adjusted to account for distance from the GPS sattelites, so each GPS receiver independently maintains it's own timebase, and the system conspires to make each discrete timebase phase and frequency align with each other.
Edit: You are asking about inertial measurement and navigation systems? If you're asking for the role of a PPS signal in something like a IMU, there isn't one. It's not used, except perhaps for setting the clock of the IMU's output timestamps (if it has timestamps).
To be clear, GPS systems are a critical component of many IMU systems, but the IMU uses the position output of the GPS, not the precision timing output.