Basics

LORAN-C was a radio navigation system before GPS which allowed a receiver to determine its position by listening to low frequency radio signals transmitted by radio beacon basestations.
They essentially sent out blips like GPS, and the device did the calculation based of the beacons' prerecorded location, and the time delay of the different signals.
A new version has been explored called eLORAN which uses more modern systems (Such as networking between radio basestations for time syncing, and error correction for improved accuracy.

Provides

Easy DIY GPS Like Navigation in Under-served Areas
Redundancy to GPS Navigation
Possibly Cheaper, Simpler, and More Precise Navigation (All that is needed for reading could be as simple as an antennae and an ossiloscope for manual, or a simple arduino circuit and an antennae for automatic
Benefits Automation like the Open Source Robotic Tractor

The Wikipedia Page on All forms of LORAN C was the last widely used version, e is being investigated, and has some current niche use