On a recent ride, my GPS stopped functioning about half way through. From other sources I have approximate times for the missing data and I know the route, so (in principle, though I'm really not sure how) I could manually create a track for the second half of the ride. But how do I combine this data with the GPS data from the first half of my ride?
Is there a way to take two separate GPX tracks and combine them into a single one? What issues arise in "syncing" overall times, speeds, etc.? Are there tools that assist in reconciling them?