I guess measure where the whales are, and hope that the flexibility of the thing you're using to re-create the line is close enough to what was used when the curve was initially created.
The order's different (the curve defining the points, as opposed to points defining the curve), but it might look like what Apple provides in their CAD files for accessory makers. Take a look at p. 362 for an example:
https://developer.apple.com/accessories/Accessory-Design-Gui...
Boat builders do talk about “fair battens”, where batten = spline, and “fair” refers to being linearly elastic. Boat building battens can be really long, so fairness is not guaranteed. Long battens are scarfed together out of pieces cut from the same timber plank to try to maximise uniformity.
The order's different (the curve defining the points, as opposed to points defining the curve), but it might look like what Apple provides in their CAD files for accessory makers. Take a look at p. 362 for an example: https://developer.apple.com/accessories/Accessory-Design-Gui...