John_V 

I use Cyclemeter on all my rides and have been doing so for just over three years now. I had the same issues as you are having when I first started using it and comparing it against my Cateye Double Wireless computer. The reason is that one is using the wheel circumference and rotation and the other is using GPS. When the Cateye quit working, I opted to use Cyclemeter exclusively and added my wife's old Garmin HRM and speed/cadence sensor to the mix via a Wahoo RFLKT+. Once I added the speed/cadence sensor, Cyclemeter was tracking as accurate as my friends Garmin 800 (± .2 mile). I've since gone to all Bluetooth sensors. If you use a Bluetooth speed/cadence sensor, you should see that problem go away. As for the altimeter, my iPhone 5c does not have one built in so I use the one from the RFLKT+, which does. It's a bit spotty but I'm in Florida, which is really flat, so altitude isn't really a big issue for us that live here. As mentioned, if you have an iPhone 6, make sure you turn on the "Barometric Altimeter" switch in Settings. It's located just under the Share section.