What if you would pull Ob to a straight line?

Ob with Irtysh
total track length: 5513.5km (1px matches approx 20m)

slitscanning over satellite imaginary along a (spline-interpolated) GPS track file
aerial image source: LANDSAT7 Global Mosaic, Courtesy: NASA/JPL-Caltech (public domain)
original track source © OpenStreetMap contributors (CC-BY-SA)

Michael Aschauer, 2010

Michael Aschauer, 2011