Tara : On the Great Barrier reef

Links :

• Tara : In the wake of Bougainville and La Boudeuse
• GeoGarage blog : Tara coral odyssea
• Earth : Tara expedition track
  

Hole the size of Maine opens in Antarctica ice

Winter sea ice blankets the Weddell Sea around Antarctica with massive extra-tropical cyclones hovering over the Southern Ocean in this satellite image from September 25, 2017. The blue curves represent the ice edge.

The polynya is the dark region of open water within the ice pack.
Photograph Courtesy of MODIS-Aqua via NASA Worldview; sea ice contours from AMSR2 ASI

via University of Bremen

From National Geographic by Heather Brady

A mysterious hole as big as the state of Maine has been spotted in Antarctica’s winter sea ice cover.

The hole was discovered by researchers about a month ago.

The team, comprised of scientists from the University of Toronto and the Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project, was monitoring the area with satellite technology after a similar hole opened last year.

The blue curves represent the ice edge, and the polynya is the dark region of open water within the ice pack.
Photograph Courtesy of MODIS-Aqua via NASA Worldview; sea ice contours from AMSR2 ASI via University of Bremen

Known as a polynya, this year’s hole was about 30,000 square miles at its largest, making it the biggest polynya observed in Antarctica’s Weddell Sea since the 1970s.

“In the depths of winter, for more than a month, we’ve had this area of open water,” says Kent Moore, professor of physics at the University of Toronto.
“It’s just remarkable that this polynya went away for 40 years and then came back.”

Localization of the polynya on the GeoGarage platform (NGA chart)

Sea ice and clouds blanket the Weddell Sea around Antarctica in this satellite image from September 25, 2017. The dark area marked by the star is the polynya.
University of Bremen

The harsh winter in Antarctica makes it hard to find holes like this one, so it can be difficult to study them.
This is the second year that a polynya formed, though last year’s hole was not as big. Scientists knew to monitor the area for polynyas this year because of last year’s discovery.

As these ice gaps typically form in coastal regions, however, the appearance of a polynya ‘deep in the ice pack’ is an unusual occurrence.

The Weddell Polynya can be seen in the Southern Ocean, above

The deep water in that part of the Southern Ocean is warmer and saltier than the surface water.
Ocean currents bring the warmer water upwards, where it melts the blankets of ice that had formed on the ocean’s surface.
That melting created the polynya.

Since the hole continually exposes the water to the atmosphere above, it is difficult for new ice layers to form.
When the warmer water cools, on contact with the frigid temperatures in the atmosphere, it sinks.
Then it reheats in deeper areas, allowing the cycle to continue.

Moore says they are working to understand what is triggering the formation of these holes again after so many years.
He thinks it is likely that marine mammals could be using this new opening to breathe.

The cooling of the warmer ocean water when it reaches the surface may also have a broader impact on the ocean’s temperature, but Moore says outside of local weather effects, scientists aren’t sure what this polynya will mean for Antarctica’s oceans and climate, and whether it is related to climate change.
“We don’t really understand the long-term impacts this polynya will have,” he says.

Links :

• CBS : Giant hole reopens in Antarctic ice for the first time in 40 years
• DailyMail : Mystery of the massive hole nearly the size of Maine that has opened up in the sea ice around Antarctica 
• USA Today : Huge, 'mysterious' hole appears in sea ice near Antarctica
• NASA : A polynya seldom seen / Polynya off the Antarctic Coast / Polynyas and the Pine Island Glacier, Antarctica / Terra Nova Bay Polynya, Antarctica

Canada CHS layer update in the GeoGarage platform

Desolation Sound is a deep water sound at the northern end of the Sunshine Coast in British Columbia, Canada.

Flanked by Cortes Island and West Redonda Island, its spectacular fjords, mountains and wildlife make it a popular boating destination.

3554 a new nautical raster chart added in the GeoGarage platform with 24 charts updated 

see GeoGarage news

Mapping the Great Barrier Reef with cameras, drones and NASA tech

In this special report, CNET dives into the ways scientists and innovators are using technology to rescue the Great Barrier Reef.

From CNET by Jennifer Bisset

New and old technologies reveal what's killing Australia's great marine wonder.

Richard Vevers, a British underwater photographer, was horrified when he returned in 2015 to a colourful reef in American Samoa he had shot a year earlier.
It had turned pure white.

Vevers, who runs a marine advocacy group called The Ocean Agency, knew bleaching, a process caused by global warming that starves coral, was the cause.
He also knew the public didn't understand the ocean's sorry shape because it couldn't see what was going on.
Cameras, he reckoned, could help.

 Great Barrier Reef with the GeoGarage platform (AHS chart)

So The Ocean Agency partnered with Google to take the search giant's Street View concept underwater at Australia's Great Barrier Reef.
It designed a military-grade scooter with an underwater camera mounted on top worth AU$50,000 (about $39,000 or £29,700).
The thousands of photographs it took were then processed by image-recognition software that group wrote for the project.

"As soon as we designed that [technology], the scientists all realised that this could revolutionise the study of coral reefs," Vevers says.
"You could suddenly look at coral reefs at a scale that was really unprecedented."

Conservationist Richard Vevers goes deep beneath the waves with his underwater camera.The Ocean Agency/XL Catlin Seaview Survey

Vevers and The Ocean Agency aren't the only researchers mapping the Great Barrier Reef, which is dying as man-made climate change wreaks havoc on its beautiful but delicate ecosystem.
Teams from Australia and around the world have projects to chart a complex, dynamic habitat that covers an area as big as Germany.
Their work is crucial to efforts to save the reef, which saw 29 percentof its shallow-water coral die last year.
After all, how can you save something if you can't see it?

The teams are using a range of technology both new and old in their projects.
In Archer Point, North Queensland, a team of indigenous rangers deploys drones to monitor the health of the reef and map the surrounding country.
A team from the University of Sydney takes thousands of photographs of the reef one second apart with GoPro cameras, stitching them into giant high-res images.
Off the reef's Whitsunday coast, marine biologist Johnny Gaskell used Google Maps to strike the location of a blue hole filled with healthy coral protected from the bleaching.

 Google Maps helped spot what has been dubbed "Gaskell's Blue Hole".

The task is daunting.
We think of the Great Barrier Reef as a single expanse of coral, but it's actually a network of 3,000 reefs that spans 2,300 kilometres (1,430 miles) along Australia's eastern coast.
Roughly 9,000 species live on it and 2 million tourists visit every year to drink in its splendour.

The sheer size of the reef makes mapping expeditions expensive, and, no surprise, funding is hard to come by.
Large ships that use remote sensing in deep waters can cost AU$40,000 (about $32,000 or £24,000) a day.
A big drilling ship used to recover parts of fossilized reefs, which shed light on past changes in climate, can cost up to AU$12 million per expedition (about $9.5 million or £7 million).
The Royal Australian Navy and Maritime Safety Queensland, a state department, shoulder some of the costs, as does the International Ocean Discovery Program, an international consortium that's the largest marine geoscience program in the world.

It's still not enough.
One estimate reckons $1 billion a year for the next 10 years is needed to have a chance to save the reef.

In the Navy

The Royal Australian Navy has protected the country's waters since before its formal establishment in 1911.
For the past three decades, it's used a homegrown technology to map the ocean floor around the country, too.

 The Royal Australian Navy uses LADS laser technology to map the ocean floor.

Known as Laser Airborne Depth Sounder (LADS), or airborne lidar, it took 20 years to develop and is now a fixture in marine mapping efforts around the world.
The concept is similar to multibeam sonar, but uses light rather than sound.

A LADS system shoots two beams of amplified light -- a green laser and a red one -- at the water below.
The green laser pierces the water and reaches the ocean floor.
The red one stops at the surface.
Each is precisely measured.
Subtract the red measurement from the green measurement and you have the depth.

Each survey is run by a team of specialists: two officers, three senior sailors and three junior sailors.
The pilots need the support so they can endure flights for up to seven hours at roughly a kilometre off the ground, which is unusually low by aviation standards.

The Navy needs to know where the coral reefs are to protect them, as well as the boats that ply the waters above them.
Chunks of the Great Barrier Reef, it turns out, are under busy shipping lanes.
An Australian government study showed that 3,947 ship voyages called at reef ports in 2012.
Port authorities and corporations expect that number to hit 5,871 in 2017, at a yearly growth rate of between 4 and 5 percent.

Alex Cowdery flew LADS sorties for the Navy when the tech debuted in the 1990s and now works for a company that sells the service to other navies.
He keeps charts from his early flights on his office walls to remind his clients this is a well-tested technology.

Since 1993, the Navy has mapped roughly 240,000 square kilometres of the Great Barrier Reef, more than half of its 347,800-square-kilometre area, he says.
The Navy flies an average of one sortie every other day to keep its charts updated.
Mapping takes discipline.

"It was exciting back then," Cowdery tells me of his early days flying LADS planes.
"And it's still exciting right now."

NASA took to the air with a new instrument that measures the wavelength of light, gathering data on healthy and unhealthy coral.

A space agency maps coral

A NASA-run project called CORAL, the Coral Reef Airborne Laboratory, took to the air from September to October in 2016 to map what's underwater.
Developed by the Jet Propulsion Laboratory, CORAL tests a next-generation hyperspectral instrument important to scientists for distinguishing healthy coral reef systems from unhealthy ones.

The project uses PRISM, an acronym for the JPL's Portable Remote Imaging Spectrometer, to capture spectrum data that previously couldn't be collected.
Spectrometers measure the wavelength of light, which provides insight into what something is made of.
The PRISM system was mounted in the belly of an airplane that flew at low altitudes above the reef and pierced the water's surface to capture high-resolution spectrum data.

The US space agency and Australia's CSIRO proposed the project five years ago but it stalled amid funding issues, a common hurdle for scientific research.
Then in 2016, money was found and the project was back on.
By September, a NASAteam decked out in caps and T-shirts bearing the organisation's iconic logo had arrived in an Australian government facility in Brisbane.


"It's pretty cool," Tim Malthus, who runs a CSIRO coastal studies group, says of working with the NASA team, which he describes as extremely well-organised.The PRISM system is a prototype that's much smaller than previous hyperspectral systems and that will eventually be deployed on satellites.
The PRISM technology has an advantage over multibeam and lidar surveys, Malthus says, because it's uniform and doesn't require corrections.

Multibeam sonar technology bounces acoustic pulses off the seabed to reveal the shape of the seafloor.

Beaman, the James Cook University researcher, brings multibeam and satellite technologies together in generating his 3D models of the reef.
Those models are now being used in a range of projects aimed at saving the reef.

The accuracy of 3D models helps researchers understand natural hazards and features of the seafloor.
For example, E-reefs, a government modeling program, uses the 3D landscapes to model particles as they move through the reef to predict how pollution travels through the area.
The model is also used to make decisions on where fishing can be allowed.

"Unless you map it, you don't know what it is," Beaman says.
"That's really what it comes down to."

Vevers, the head of The Ocean Agency, says that's what the Google Street View project was all about.
If people see the Great Barrier Reef and other reefs around the world, they'll be more emotionally involved in saving them.

The Ocean Agency technology that was designed for the Street View project is now being used to document the state of reefs in 25 countries around the world.
Vevers says the results will be made public so everyone can see what's at stake.

"Everyone feels like a child when they see that new environment for the first time," Vevers says.
"You just get excited."

Links :

• GeoGarage blog : A computer just changed the Coral research ... / Scientists capture amazing views of the Great ... / Google SeaView : Ocean survey launches on Great Barrier Reef / Great Barrier Reef: 93% of reefs hit by coral ... / The quest to save coral reefs / Vast reef discovered behind Great Barrier Reef / David Attenborough's Great Barrier Reef ... 

Technology in focus: GNSS Receivers

Trimble Catalyst software defined receiver with an Android device

connected capable of RTK solutions.

Image courtesy: Trimble.

From Hydro Int. by Huibert-Jan Lekkerkerk

Evolution Towards Higher Accuracies

GNSS has now been operational in the surveying industry, and especially in hydrography, for more than 25 years.
Where the first receivers such as the Sercel NR103 (once the workhorse of the industry) boasted 10 parallel GPS L1 channels, current receiver technology has evolved to multi GNSS, multi-channel and multi-frequency solutions.
In this article, we will look at the current state of affairs and try to identify the areas where development can be expected in the years to come.

In hydrography, we can distinguish between ‘land use’ and ‘marine use’ of our GNSS receivers.
Especially in the dredging, nearshore and inshore domains both land survey as well as maritime receivers are employed.
They do not differ in their basic capabilities such as positioning accuracy of number of channels (and GNSS) they can receive.
The main differences lie in the form factor of the receiver (portable for land survey, rack mounted for marine survey) and the method of operation.
Whereas a land survey receiver is almost always combined with a separate controller running extensive data acquisition software, the marine receiver is more and more of the black box type with at most a minimal display (and sometimes none).
Setting of the pure marine receiver is done using a network interface with the computer browser whereas the positioning data is transported over the network (or if required RS232) connections to the data acquisition software.

 GNSS constellations, their associated frequencies and the number of satellites ultimately transmitting these signals.

Source: gsa.europa.eu

GNSS Signal Reception

If we look at the major developments over the last few years, then it is the continuous addition of systems to the satellite constellation such as Beidou and Galileo as well as the longer existing GPS and Galileo.
But even within the existing systems developments are ongoing, with new frequencies such as L1C, L2C and L5 being added to the spectrum of available signals.
Most receivers are ahead of actual GNSS operations and will supply their receivers prepared to receive all GNSS and the maximum number of satellites and signals available.
As a result, a modern receiver may boast over 400 channels with an average of around 200 channels in a receiver.
A single channel will receive a single frequency from a single satellite for a single GNSS.
Thus, current high-end receivers can track over 125 satellites at the same time! Be aware however that not all systems are currently at full operational capability (FOC).
GPS and Galileo are at FOC whereas both Beidou and Galileo have limited coverage.
Those working in the far East will benefit from Chinese Beidou, the Japanese QZSS and the Indian IRNSS as the local coverage is very stable.
However, elsewhere in the world Beidou coverage is still marginal and QZSS and IRNSS coverage non-existent due to their regional character.

 Percentage of GNSS receivers able to receive a certain constellation in 2016.

Image courtesy: gsa.europa.eu

Signal Processing

The processing of GNSS signals is still being improved although this is more evolutionary than revolutionary.
The availability of ever greater processing power allows the GNSS receiver to allow, for example, for a better multi-path rejection.
Also, receiving weak signals and being able to detect the direct signal from a confused set of GNSS signals is currently possible..
Better tracking and multi-path rejection is not only the result of higher processing power but also of developments in antenna design.
Thus, it becomes easier to move the GNSS in difficult situations whilst still keeping relatively stable and accurate positioning.
The increased computing power also makes it easier to implement algorithms that have an increased accuracy when processing multiple GNSS signals at the same time.
The increased processing power also makes it easier to integrate Precise Point Positioning (PPP) and heading solutions on a single receiver board making the units effectively smaller.

In general, the use of PPP seems to be increasing with major suppliers of correction signals now supplying PPP corrections for all four global GNSS.
Most professional receivers are now dual frequency receivers, but these are expected to be replaced by triple frequency systems as the Galileo commercial service becomes available and GPS will have introduced L5 in more satellites.
Triple frequency processing promises even more accurate RTK and PPP solutions with faster initialisation times.

A modern GNSS receiver will start within a minute even in situations where it has not been started for a while if connected to the internet such as in most land survey receivers.
Without assisted-GNSS start-up times can be longer for a cold start.
Re-acquisition times are now well below 15 seconds with the more high-end receivers boasting re-acquisition times of just a few seconds in most situations.

Software Defined Receiver

One of the latest developments is the low-cost software defined receiver.
Where a traditional receiver has all the processing power in a standalone device, the software defined receiver uses the computing power of an existing device.
This means that the actual receiver is reduced to an antenna and analogue-digital converter to allow the GNSS signals to be processed by the positioning device, for example, a tablet.
The lack of dedicated hardware means that the software defined receiver is relatively cheap and lightweight and can be integrated into existing applications that have direct access to the positioning system rather than to just the output.

Data Output

As stated earlier, most modern receivers employ internet connection to transmit their data to the survey computer.
Serial connection (RS232) is still available with modern receivers although the number of ports are being reduced in favour of the network connection.
The frequency of data output is becoming higher with less latency for the signals with a higher update rate.
While in the past the interpolation of ‘intermediate’ positions between the 1s formal output was very visible, modern GNSS receivers can output at relatively high frequencies without a significant degradation of positioning accuracy.
However, most manufacturers still advise using the 1 second output if the utmost accuracy is required in favour of update rates of 20 – 100Hz.
The main advantage of the higher update rates is that for applications where this high update rate is required such as in dynamic positioning it is available with a limited degradation of positioning accuracy, especially when operating in PPP.

Links :

• GeoGarage blog :  Superaccurate GPS chips coming to ... / New Air Force satellites launched to improve GPS / Europe's own satnav, Galileo, due to go live / Happy 20th Anniversary, GPS! / Behind the master controls of gps  ...