Does anyone use an outdoor gym?

There's an outdoor gym outside my flat in London which I've just started using, in the name of seeing if I can keep doing the free one outside before investing in an actual gym membership.

Does anyone have idea how to log the calories I've worked?
Been doing this machine every day:
http://www.tgogc.com/useagym/how-to-use/equipment.html?id=84
(don't know how to make it clicky, sorry) and the best match I can come up with is calling it a low resistance stationary bike, as they call it a 'cross trainer', but the calories burned on a gym one look far too high for it to be that.

Does anyone have any suggestions please?