Error Budget for Chronometric Levelling Across a 1000 Kilometre Fibre Clock Network

A continental fibre network does not fail because its clocks are insufficient; it fails, if it does, in the accumulation of small link terms and in correlated environmental terms that do not average down with segment count. This study builds a segment-by-segment budget for a thousand-kilometre chain. The design question is concrete: with ten repeater segments, two endpoint clocks and a stated tide-model term, what height uncertainty survives, and which term should money be spent reducing first? The computed results, taken from the deposited script, are as follows in summary: The computed segments is 10. The computed link_per_seg is 2e-19. The computed clock_each is 1e-18. The computed rss_frac is 1.55e-18. The computed tide_frac is 5.46e-19. The computed total_frac is 1.64e-18. The computed total_height_cm is 1.51. The computed clock_only_cm is 1.3. The study is a computation from stated assumptions, not a measurement, and its figures should be read at the precision those assumptions support. SIMULATED, NOT MEASURED.