The kms. provided on this site use GPS calculations within our route database, and are considered pretty accurate (unless the route itself is misplotted). This is the only independent site that provides independently computed kms. Every other site/publication uses the Govt. computed kms.
Many users compare IRI kms. with the Govt. kms. and may say IRI is wrong. However, "wrong" or "right" is only relative. Whenever there is a variance, we double-check the route and stations. In most cases, we let the variance in kms. stay, because the plotting is found to be correct, and according to this site, our kms are accurate and other sources are wrong (relatively speaking). There may be a slight variance in kms. between IRI and other...
more... sites, but who is wrong or right is only a relative thing.
Thanks.