A hill on a seemingly flat ride

Summary Data
Total Time (h:m:s)	1:33:33	3:10 pace
Moving Time (h:m:s)	1:32:56	3:09 pace
Distance (mi )	29.43
Moving Speed (mph)	19.0 avg.	27.3 max.
Elevation Gain (ft)	+565 / -564
Temperature (°F)	61.4°F avg.	62.6°F high
Wind Speed ( mph)	N 0.0 avg.	N 0.0 max.

Start time: 06:16:40AM (CDT)
Odometer: 1061.72

My inclination is to say that this trail is entirely flat, but at numerous times I felt like I was going distinctly uphill or downhill for long stretches at an almost imperceptible grade. I think I noticed it most because sometimes, without actually causing me to slow down, pushing forward was more labored than at other times.


Interesting that on this ride the elevation is perfectly symmetrical. I am sure that the Chicago rides also bear such symmetery, but it is harder to notice there since we do not have such a distinct climb from 12 to 81 feet from start to finish.