For the first time sea level has been mapped from space with GPS reflections, according to new research published in Geophysical Research Letters by the UK’s National Oceanography Centre (NOC) scientists.
Information from these GPS signal reflections can be potentially used by scientists to monitor ocean currents by measuring the slopes currents cause in the ocean’s surface.
Dr Paolo Cipollini from NOC, who co-authored this research, said “the sea surface is not flat at all, especially when looked at over long distances. The largest ‘bulges’ are due to variations in the Earth’s gravity field. On top of those there are smaller, shorter variations due to sea surface currents. We are really encouraged by our results since it demonstrates for the first time that we are able to map the overall sea surface height from space using the GPS-reflections technique. This leads us to think that in the near future we should be able to map currents from space by detecting even smaller variations in sea surface height.”
GNSS-Reflectometry (GNSS-R) is the general term for reflectometry using navigation signals, including GPS as well as the European equivalent Galileo. The advantage of using GNSS-R is that it uses the GNSS transmitters already in orbit, and the lightweight, low-power receivers can be launched into space relatively cost-effectively. Existing satellite altimeters, although very accurate, are not in enough number to sample the ocean well at scales below 100 km. A constellation of GNSS-Reflectometry receivers would provide a thirty-fold improvement on the amount of data that could be gathered. Such a constellation will be launched in late 2016 as part of the NASA CYGNSS mission.
Photo credit: Paolo Cipollini from the NOC