From orbit - it's the only way to be sure.

[the_s_guy]

I wonder if Mexico would be interested in a transoceanic channel able to pass two Emma Mærsks side by side?

*does the calculations*

Hm. About one cubic kilometre of rock to be blasted, a number of roads to be turned into bridges, and I'm not entirely sure how to rig existing rivers to allow them to cross over the resulting channel. Maybe run them underneath somehow.