Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers Improving GPS Accuracy in the 3rd Dimension

19.08.2011
Researchers who are working to fix global positioning system (GPS) errors have devised software to take a more accurate measurement of altitude – particularly in mountainous areas.

The software is still under development, but in initial tests it enabled centimeter-scale GPS positioning – including altitude – as often as 97 percent of the time.

Researchers hope the software will help to improve the vertical accuracy of measurements in potentially hazardous regions at high altitudes, such as areas of soft, loose land that may be prone to landslides. They also claim that their software could be used to measure how quickly glaciers at high altitudes are melting.

The GPS is most commonly known for its ability to provide on-the-spot locations for drivers, but this application is just one of many possible uses, explained Dorota Grejner-Brzezinska, professor of civil and environmental engineering and geodetic science at Ohio State University. As the level of GPS precision increases, so do potential applications for scientific research.

While drivers are generally concerned with tracking their own location in two dimensions on the earth’s surface, the third dimension of altitude has always been available through GPS – just with lower accuracy than that of the horizontal coordinates.

Recently, Grejner-Brzezinska and her colleagues from the University of Warmia and Mazury in Poland have developed software that will allow GPS to relay locations to within a few centimeters’ accuracy, including altitude. While this high level of precision is not necessary for driving directions, it is necessary for recognizing small shifts in topsoil that may lead to dangerously destructive landslides.

She explained that a lot is going on behind the scenes during a typical use of GPS.

GPS satellites transmit information in the form of radio waves to the GPS receiver held by the user. At the same time, the signals must also travel to at least one other ground-based receiver to obtain a location reference, which allows the user’s receiver in turn to accurately calculate its own position in 3D. Before the satellite signals reach the receivers, they must travel through Earth’s atmosphere, which results in time delays that affect accuracy.

When the user’s receiver and the reference receiver reside at drastically different altitudes, however, each location experiences different amounts of time delay, which complicates matters even further. So, in mountainous regions where height differences can vary greatly over a short distance, acquiring the altitude of locations to within a few centimeters is difficult.

“Time is the heart that drives GPS, so it is important that we have a proficient method that accounts for delays from earth’s atmospheric layers,” said Grejner-Brzezinska. “It would be ideal for all GPS signals to travel in a straight line directly to their destination, but due to electron interaction and refraction in the lower atmosphere, the signal’s path is far from straight,” she continued.

Electron interaction and tropospheric refraction effectively re-route the GPS signal, which means that the signal travels an extra distance and requires extra time, said Grejner-Brzezinska.

She and her colleagues looked specifically at troposphere delays – those caused by the lowest level of the atmosphere. Their study can be found in a recent issue of the journal Measurement Science and Technology.

In the past, scientists have tried to account for troposphere delays by using basic models of Earth’s atmosphere, said Grejner-Brzezinska. But these models may not fully account for changes in the weather or temperature, which can have a significant effect on the amount of interference the GPS signals experience on their way down to earth.

Not only weather and temperature, but also the height difference between two stations can greatly affect the accuracy of a GPS-based height determination.

Using ground station receivers located in the Carpathian Mountains in Poland – a region known for its steep slopes – the researchers collected GPS information over a 13-hour period.

They looked at two pairs of receivers with different height changes. The first pair was located 72 kilometers apart and had a height difference of 32 meters. The second pair was 66 kilometers apart with a total height difference of 380 meters.

“We figured that the easiest scenario would be provided by the receivers with 32-meter height difference, and the most challenging one with a height difference of 380 meters,” said Grejner-Brzezinska.

Using processing software developed originally in Grejner-Brzezinska’s lab at Ohio State, and further expanded by her research collaborators at the University of Warmia and Mazury in Poland, the researchers applied three different methods to measure GPS accuracy for the receivers.

The results showed that, out of the three methods of handling tropospheric delay in GPS measurements that were tested, there was one that provided an accurate location, including the height of the receivers, 97 percent of the time.

“Of the three methods we tested, the third and most accurate was also the most complicated,” said Grejner-Brzezinska. “This method was developed by our team, and required knowledge of three or four reference stations in order to perform the calculations properly.”

The other two methods did not require the use of multiple reference points – just a single one – but their levels of accuracy did not match the third method’s positioning capabilities.

Further testing will follow. But this early study shows that GPS accuracy for altitude estimation can be improved, and may lead to the precision estimates that researchers need to analyze, for example, the stability of mountaintops and glaciers with 10-minute temporal resolution.

This research was funded by the European Space Agency Plan for European Cooperating States project and a grant from the Polish Ministry of Science and Higher Education.

Grejner-Brzezinska’s collaborators at the University of Warmia and Mazury include Pawel Wielgosz, Slawomir Cellmer and Zofia Rzepecka.

Contact: Dorota Grejner-Brzezinska, 614-292-8787; dbrzezinska@osu.edu
Media Contact: Pam Frost Gorder, (614) 292-9475; Gorder.1@osu.edu
Written by Jessica Orwig.

Pam Frost Gorder | Newswise Science News
Further information:
http://www.osu.edu

More articles from Information Technology:

nachricht Cloud technology: Dynamic certificates make cloud service providers more secure
15.01.2018 | Technische Universität München

nachricht New discovery could improve brain-like memory and computing
10.01.2018 | University of Minnesota

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>