UltraTrac for Biking

Ultratrac IS a GPS usage setting.  There are no suboptions for Ultratrac.  It is barely adequate for hiking/walking.  Useless for anything else.

I would recommend something else.

Use GPS only when riding - it will give you good enough accuracy. When you stop, disable the GPS manually, to save battery life. I've noticed quite noticeable battery drain while I am resting, not when moving. And this makes sense, because I usually stop under a tree or under some sort of a roof, which blocks the signal and makes the watch work much harder. This way, I have managed to do an 8 hour ride only at the cost of 1/5 of battery charge.

The downside, obviously, is that you have to remember to turn off and on the GPS on every break.

On the positive side, I would recalibrate everytime you turn it on, so position and elevation would be very accurate. Second, you would be able to do even a two day ride on a single charge.

Ultratrac is broken. If you only want to have a rough gps trace on the map with your activity you will be fine. Garmin decided not to interpolate data between gps  wakeups (in ultratrac it wakes every minute), so the speed and distance is completely wrong (during hiking with ultratrac in my instinct my distance was half the real distance - and more than half compared to my wives Vivoactive4 with regular gps...). The only viable use for this feature IMO is to have gps record your route so you can use Instincts' navigation to go back the way you came. 

EDIT: You could download GPX file from your watch and try to do the interpolation yourself - but it doesn't seem to be easy to do.