Featured Research

from universities, journals, and other organizations

New tide gauge uses GPS signals to measure sea level change

Date:
May 21, 2014
Source:
Chalmers University of Technology
Summary:
A new way of measuring sea level using satellite navigation system signals, for instance GPS, has been implemented. Sea level and its variation can easily be monitored using existing coastal GPS stations, the scientists have shown.

When satellites pass over the sky, the GNSS tide gauge uses signals direct from the satellite and signals reflected off the sea surface to measure the sea level.
Credit: Johan Löfgren

A new way of measuring sea level using satellite navigation system signals, for instance GPS, has been implemented by scientists at Chalmers University of Technology in Sweden. Sea level and its variation can easily be monitored using existing coastal GPS stations, the scientists have shown.

Measuring sea level is an increasingly important part of climate research, and a rising mean sea level is one of the most tangible consequences of climate change. Researchers at Chalmers University of Technology have studied new ways of measuring sea level that could become important tools for testing climate models and for investigating how the sea level along the world's coasts is affected by climate change.

Johan Löfgren and Rüdiger Haas, scientists at Chalmers Department of Earth and Space Sciences, have developed and tested an instrument that measures the sea level using radio signals from satellite navigation systems: a GNSS tide gauge (GNSS stands for Global Navigation Satellite System).

"The global mean sea level is rising because of climate change, but the change depends on where you are in the world," says Rüdiger Haas. "We want to be able to make detailed measurements of sea level so that we can understand how coastal societies will be affected in the future."

The GNSS tide gauge uses radio signals from satellites in orbit around Earth that are part of satellite navigation systems like GPS and Glonass (Russia's equivalent of GPS).

"We measure the sea level using the same radio signals that mobile phones and cars use in their satellite navigation systems," says Johan Löfgren. "As the satellites pass over the sky, the instrument 'sees' their signals -- both those that come direct and those that are reflected off the sea surface."

Two antennas, covered by small white radomes, measure signals both directly from the satellites and signals reflected off the sea surface. By analyzing these signals together, the sea level and its variation can be measured, up to 20 times per second. The sea level time series is rich in physical phenomena such as tides (caused mostly by the gravitational pull of the Moon and the Sun), meteorological signals (high and low pressure), and signals from climate change. Through advanced signal processing, these signals can be studied further.

The new GNSS tide gauge has the advantage that it can measure changes in both land and sea at the same time, in the same location. That means that both long-term and short-term land movements (post-glacial rebound and earthquakes) can be taken into consideration.

"Now we can measure the sea level both relative to the coast and relative to the centre of Earth, which means we can clearly tell the difference between changes in the water level and changes in the land," says Johan Löfgren.

This summer the tide gauge station at Onsala Space Observatory will be complemented, in collaboration with SMHI, the Swedish Meteorological and Hydrological Institute. Other high-precision instruments will be installed to work together with the GNSS tide gauge.

"Our tide gauge station will become part of a network of stations along the coast of Sweden that will be able to monitor changes in the water level to millimetre precision well into the future," says Gunnar Elgered, professor at Chalmers Department of Earth and Space Sciences.

The scientists have also shown that existing coastal GNSS stations, installed primarily for the purpose of measuring land movements, can be used to make sea level measurements.

"We've successfully tested a method where only one of the antennas is used to receive the radio signals. That means that existing coastal GNSS stations -- there are hundreds of them all over the world -- can also be used to measure the sea level," says Johan Löfgren.


Story Source:

The above story is based on materials provided by Chalmers University of Technology. Note: Materials may be edited for content and length.


Journal Reference:

  1. Johan S Löfgren, Rüdiger Haas. Sea level measurements using multi-frequency GPS and GLONASS observations. EURASIP Journal on Advances in Signal Processing, 2014; 2014 (1): 50 DOI: 10.1186/1687-6180-2014-50

Cite This Page:

Chalmers University of Technology. "New tide gauge uses GPS signals to measure sea level change." ScienceDaily. ScienceDaily, 21 May 2014. <www.sciencedaily.com/releases/2014/05/140521094501.htm>.
Chalmers University of Technology. (2014, May 21). New tide gauge uses GPS signals to measure sea level change. ScienceDaily. Retrieved September 2, 2014 from www.sciencedaily.com/releases/2014/05/140521094501.htm
Chalmers University of Technology. "New tide gauge uses GPS signals to measure sea level change." ScienceDaily. www.sciencedaily.com/releases/2014/05/140521094501.htm (accessed September 2, 2014).

Share This




More Earth & Climate News

Tuesday, September 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Thousands of Fish Dead in Mexico Lake

Raw: Thousands of Fish Dead in Mexico Lake

AP (Sep. 2, 2014) — Over 53 tons of rotting fish have been removed from Lake Cajititlan in western Jalisco state. Authorities say that the thousands of fish did not die of natural causes. (Sep. 2) Video provided by AP
Powered by NewsLook.com
Raw: Iceland Volcano Spewing Smoke

Raw: Iceland Volcano Spewing Smoke

AP (Sep. 2, 2014) — The alert warning for the area surrounding Iceland's Bardarbunga volcano was kept at orange on Tuesday, indicating increased unrest with greater potential for an eruption. Smoke is spewing from the volcano, and lava is spouting nearby. (Sept. 2) Video provided by AP
Powered by NewsLook.com
U.N. Says Ebola Travel Restrictions Will Cause Food Shortage

U.N. Says Ebola Travel Restrictions Will Cause Food Shortage

Newsy (Sep. 2, 2014) — The U.N. says the problem is two-fold — quarantine zones and travel restrictions are limiting the movement of both people and food. Video provided by Newsy
Powered by NewsLook.com
Sharks Off the Menu and on the Tourist Trail in Palau

Sharks Off the Menu and on the Tourist Trail in Palau

AFP (Sep. 2, 2014) — Tourists in Palau clamour to dive with sharks thanks to a pioneering conservation initiative -- as the island nation plans to completely ban commercial fishing in its vast ocean territory. 01:15 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins