Swtich from waypoints to turn by turn

Today I did a race with 2 waypoints.  In the beginning it showed the distance to the next waypoint (at 10km500).  But after 10km500 things became weird.  First of all instead of starting to show the distance to the second waypoint it switched to showing the distance to the next turn.  I didn't think about it at first but I do remember my watch told me at the start it would show only the first 50 points and the last 29 would not be shown.  Then the second weird thing.  According to my watch I was at the first waypoint after 10km500, but actually the first waypoint was after 9km750 because the course didn't correspond with the route I got.  So actually I only had to remember the distance on witch distancemarker the waypoint are to have the same information.  Anyone knows or has made an app that shows the distance along the course to the next waypoint based on the coordinates and not on the distancemarker on the course?