Context Navigation

Timing

-                      v1
+                      v2
 If there is a timing error between navigation and imagery, movements of the aircraft will be incorrectly compensated for early or late in the imagery.  This means that in straight flight, timing errors are not visible.
 The symptom of a timing error is a wobble in a known-straight feature (e.g. a road) that corresponds to a matching but mistimed wobble in the aircraft flightline (see the edge of the swath for these).  If there's not a matching wobble, it's more likely to be a DEM mismatch caused by datum or geometric shift issues.
+The symptom of a timing error is a wobble in a known-straight feature (e.g. a road) that corresponds to a matching but mistimed wobble in the aircraft flightline (see the edge of the swath for these).
+Note that "matching" means a movement of image placement that would compensate for the movement of the aircraft.  It's difficult to correctly judge which direction the wobble should be in (as it depends on the direction of flight and the timing error), but the size of the shift should match.
+If there's not a matching wobble, it's more likely to be a DEM mismatch caused by datum or geometric shift issues.
+== Image with timing error ==
+[[Image(gpt-0.2.png, 500px)]]
+== Image with correct timing ==
+[[Image(gpt-0.07.png, 500px)]]