Maintaining VFR altitudes when following N/S roads/rivers

BT writes:

What you are doing is not pilotage.
Fly a straight line based on compass and wind correction computations.
Time between visual points, towns, bridges, etc to compute ground speed.
Correct the heading slightly based on "observations" from pilotage.

just following a meandering river or road is not pilotage.

Pilotage is supposedly navigation by visual landmarks, which presumably
includes roads and rivers. Successful pilotage implies that you can navigate
with just the visual features and a chart. If you are using calculations to
determine your position, it's more like dead reckoning. I do try to navigate
that way, too, but periodically I like to practice navigation by visual
features on the land below alone.