I don't understand the speed reading for the CRS-12 misson's stage 1.
While being around an altitude of ~100km the minimum speed that is shown in the webcast for stage 1 is ~1600km/h.
If the speed shown were the horizontal speed measured relative to earth it should reach zero at some point, as it turns around and flies back to the Landing Zone in Cape Caneveral.
It can't be the vertical speed as it is still a couple of thousand km/h while being on a constant altitude.
A combination of the two couldn't be much more than 100km/h at some point during the turnaround / minimal climb period.
So how am I to read that velocity data, does anyone know?
There is a nice plot of the trajectory in the image shown below, which seems plausible because of the fact that the stage 1 actually lands only a few km away from the lift-off site, but the speed data shown in the video simply does not match with that plotted trajectory.
So what am I missing here?
After looking at the great answers below i now realize that even with the 'not to scale' image above you can understand whats happening (once the nice ppl on stackoverflow explain it to you ;) ), the turnaround is 'roughly' circular, so imagening it as almost circular explains why the speed does not drop to zero, the combination of vertical + horizontal movement keeps the total speed high.
Thanks guys :)