Folks, have a look at what Hildy said in his first post. "If you look at the track side-on in google earth...". He isn't using GPS to as a navigation tool in the circuit, he's using it to review his flight performance back home in the comfort of his computer chair.
I did (and still do) exactly the same thing with a small portable GPS recorder that sits tucked out of the way, silently remembering what I've done. When I was learning circuits, it taught me that those nice 90deg turns were anything but, and these days I still review every flight later that night for track and altitude accuracy.
Hildy, the most likely reason that your altitude track doesn't look as expected is that the GPS will be 'smoothing' the recorded path - it assumes that a sudden change in direction (ie no longer descending) must be wrong, and so it continues your downward path for a little while. You may be able to remove the smoothing if you dig around in the configuration of the GPS or in the program that you use to upload the data, but I wouldn't worry too much. You know with much more accuracy whether you hit the ground hard or rounded out too high than any GPS recorder ever will.
(p.s. I just looked at your track. Given that I can see where you wandered around in the instructors office and when you did the pre-flight check, I'm guessing you were using a sports gps watch. Right? :thumb_up:)