New results from a satellite measuring the earth's gravity have just been released enabling much more accurate mapping.
The Secretariat of the Pacific Community's geographic specialist, Dr Wolf Forstreuter, says the Pacific region was mapped relatively late and he hopes the new data will help governments.
He says changes can also be recorded and mapped by the WorldView 2 satellite which has been in space for a year.
"Islands are moving. Moving partly especially Tonga very fast. This is related to the tectonic movement of islands and for very small low lying islands, current drifts sands away from one side of the island and builds sand on the other side of the island."
Dr Forstreuter says the higher resolution pictures from the satellite could also help in mapping crops or tracking damage from natural disasters.