Is a subset of a problem solution, used to recreate complete solution considered a heuristic? This is a question about a nomenclature - we already have the algorithm/solution, but we're not sure whether it qualifies as utilizing heuristics or not.



feel free to skip the problem explanation:


  A friend is writing a path-finding algorithm - an autopilot for an
  (off-road) vehicle in a computer game. This is a pretty classic
  problem - he finds a viable, not necessarily optimal but "good enough"
  route using the A* algorithm, by taking the terrain layout and vehicle
  capabilities into account, and modifying a direct (straight) line path
  to account for these. The whole map is known a'priori and invariant,
  though the start and destination are arbitrary (user-chosen) and the
  path is not guaranteed to exist at all.
  
  This cookie-cutter approach comes with a twist: limited storage space.
  We can afford some more volatile memory on start, but we should free
  most of it once the route has been found. The travel may take days -
  of real time too, so the path must be saved to disk, and the space in
  the save file for custom data like this is severely limited. Too
  limited to save all the waypoints - even after culling trivial
  solution waypoints ('continue straight ahead'), and by a rather large
  margin, order of 20% the size of our data set.
  
  A solution we came up with is to calculate the route once on start,
  then 'forget' all the trivial and 90% of the non-trivial waypoints.
  This both serves as a proof that a solution exists, and provides a set
  of points reaching which, in sequence, guarantees the route will take
  us to the destination.
  
  Once the vehicle reaches a waypoint, the route to the next one is
  calculated again, from scratch. It's known to exist and be correct
  (because we did it once, and it was correct), it doesn't put too much
  strain on the CPU and the memory (it's only about 10% the total route
  length) and it doesn't need to go into permanent storage (restarting
  from any point along the path is just a subset of the solution
  connecting two saved waypoints).




Now for the actual question:

The pathfinding algorithm follows a sparse set of waypoints which by themselves are not nearly sufficient as a route, but allow for easy, efficient  calculation of the actual route, simultaneously guarantying its existence; they are a subset of the full solution. 

Is this a heuristic approach?

(as I understand, normally, heuristics don't guarantee existence of a solution, and merely suggest more likely candidates. In this case, the 'hints' are taken straight out of an actual working solution, thus my doubts.)
Whether or not a label fits any particular instance depends on what you're using the label for. If something specific is riding on whether this approach is a 'heuristic' or not, that context is important.

But I wouldn't call this a heuristic, because I think of that as a shortcut for solving a problem, not either storing a solution or reformulating the problem (which is how I'd think of this).