Complex sentence: The sand is sprayed by the dredging ships, which are guided by DGPS, on to the required area in a process known as rainbowing because of the arcs in the air when the sand is sprayed.
Split into simpler sentences: The sand is sprayed from the dredging ships, which are guided by a Digital Global Positioning System, on to the required area in a process known as rainbowing. The process is known as rainbowing because of the arcs produced in the air when the sand is sprayed.