Science is based upon repetition. If you accept the idea that one crossing is immediately reliable, then you must in turn accept that the world is flat due to experiments such as the Bedford Level Experiment.
Worsley died in the attempt of crossing Antarctica: one of many.
Therein lies your problem, the Bedford Level Experiment proved the Earth's Curvature, In fact it was taught in schools as proof of curvature, up until satellite images became available.
The Definitive Bedford Level Experiment was done by Henry Yule Oldham.
"Oldham used a plate camera and theodolite for his careful observations along the length of the river and he presented his results at an illustrated lecture held at the British Association for the Advancement of Science.[5][6] His experiment, because of its photographic proof, is regarded as definitive and was taught in schools[7] until images taken from orbiting satellites became available."
In any event, an experiment which is subject to errors of method and interpretation, is not the same logically, as crossing a continent, you either crossed it or you didn't, No room for systemic error or interpretation.
As I said before, Tiddles brain function seems to be impaired. He keeps bringing up things long since dismissed by the rest of the flat earth community.