You wonder how a ship could run aground in the age of GPS, but it's happened before.
Excerpt from the book Taming Hal:
http://ti.arc.nasa.gov/m/profile/adegani/Grounding%20of%20the%20Royal%20Majesty.pdf

The short version is that the GPS antenna cable failed, so the GPS switched to ded reconing mode and kept on displaying what appeared to be a valid position, as well as feeding it to the autopilot.

You can blame it on a very poor human interface design, but the humans were also complacent and ignored a number of warning signs that all was not well, "bending the map" as described in Deep Survival.