Pretty Parallax Planes

While scanning the European Space Agency’s (ESA) Sentinel-2 satellite images for signs of the Sanchi oil slick, I came across an unusual sight of what appeared to be three, brightly-colored aircraft flying in tight formation. I’m not enough of a GIS rookie to be fooled into thinking China’s latest stealth jets were malfunctioning, what I was observing was a single aircraft’s image split into three spectral bands of red, green, and blue.

This flight was snapped by Sentinel-2 on its way to Tokyo (flight data from Flightradar24.com).

To explain why this happens, we need to take a look at the source of these images: Sentinel-2’s MultiSpectral Instrument (MSI) sensor. This can be thought of as a very advanced camera that can see beyond the usual visual spectrum and into the near-infrared (great for monitoring vegetation) and shortwave infrared. Instead of just one sensor in a camera, the MSI sensor has 12 in a row. For a more technical explanation, take a look at ESA’s guide on the MSI sensor here. Imagine a push-broom with 12, wide bristles and you’ll have an idea of how these sensors sweep across the Earth as the satellite flies overhead. Each sensor splits the image into 10 different spectral bands using a stripe filter which means not only is each band detected at a slightly different angle, they are also detected at slightly different times. What this means for an image like the one above, a “true color” composite made up of the MSI’s red, green, and blue bands, is that when the bands are combined, an assumption has to be made about how far away the object is to correct for the parallax and “focus” the image on the target — and for earth-observation systems like Sentinel, the target is the surface of the earth. An element of parallax is factored in when we combine the bands in the same way that our brains adjust for the parallax of the different angles our eyeballs are seeing. This is called orthorectification. For an example of this, hold your finger halfway between this screen and your face and focus on these words. As well as being a bit blurry, you should be seeing more than one finger. In the same way, the RGB bands are combined with the focus on the surface of the Earth so an aircraft at a higher altitude splits into three images, one for each band. Since this Airbus A321 was cruising at an altitude of about 33,000 feet, the aircraft’s position was projected onto the Earth’s surface resulting in three different images, one for each of the bands.

The time difference between when each band is detected also adds to the offset. This isn’t noticeable for stationary or slow-moving objects but an aircraft is moving fast enough to see a difference. In the image we found, the aircraft’s speed, about 550kts (according to Flightradar24.com), is probably the biggest cause of the shift between images but if you look closely at the contrails, you can see some sideways drift between the first and last image of the plane. The image below, from just off the east coast of Bulgaria, better highlights the two effects of the forward motion of the aircraft and the sideways shift due to parallax.

Example of parallax off the east coast of Bulgaria.

If we really wanted to fix the aircraft’s image, we would need to adjust for the parallax at that distance as well as the delay between each band’s detection (to account for the aircraft’s speed). The result would be that the aircraft would now be one, complete image but everything else would be a multicolor mess.

For more info on this effect, check out this post by Tyler Erickson, or some direct information from the European Space Agency (skip to chapter 2.5).

What We Can See, In Heat Maps

Here at SkyTruth, we depend on our friends at the European Space Agency (ESA), NASA and the U.S. Geological Survey (USGS) for their support in providing access to data and images from their fleets of government-operated satellites.

The Sentinel missions are pairs of satellites that are part of the Copernicus program at ESA. Sentinel 1 is of particular use to us for offshore oil pollution monitoring as the radar sensor it carries can penetrate cloud cover and highlight oil slicks against water. The optical-infrared imaging system on Sentinel 2 covers a wide range of spectral bands that we can process to create a variety of true-color and false-color images, which we use to study environmental issues like drilling, mining, and deforestation.

Many folks assume these Earth-Observing satellites are continually collecting images as they orbit overhead, but for most systems that is not the case. Much of the time the sensors are turned off to save power, to conserve onboard storage, because of limited communications bandwidth, or because the operators just aren’t interested in covering large areas where there isn’t much demand for imagery (far out at sea, or over vast deserts, for example).  We thought it would be interesting and useful to analyze the archives of imagery collected by these systems, and map where they’ve taken images, to get a sense for how frequently they are covering various parts of the planet.   

The heat maps below show the locations of all the images collected by Sentinels 1 and 2 since they became active, and for a recent calendar year (2016). As you can see, the distribution of images is not at all uniform, with a strong bias toward covering Europe and the Arctic. Most of the ocean doesn’t get imaged at all. Please note that “scene count” means the image count at any particular point on the map.

The U.S. Geological Survey (USGS) manages the images produced by NASA-built satellites in the Landsat program which has been imaging the Earth since 1972, much longer than any other civilian satellite imaging program. Currently, only Landsat 7 and 8 are in operation (with Landsat 9 planned for 2020) and, similar to Sentinel 2; they provide us with instrumental data collected across a range of spectral wavelengths which we can process into color images.
Like the Sentinel satellites, the Landsat archives have sparse coverage in the ocean. While there is some pro-northern hemisphere bias, the operators of Landsat 8 have made a concerted effort to distribute the collection of imagery more evenly over all of the Earth’s land masses, with the exception of a few large areas that are chronically impaired by heavy haze, dust, smog, or cloud cover. Can you pick them out?  

Satellites Leave No Place to Hide for Rogue Thai Fishing Fleet

Despite a dearth of monitoring and law enforcement in the remote Saya de Malha bank, there’s nothing secret about what’s going on in this distant area of the Indian Ocean east of Madagascar.

Last month, Greenpeace published a report asserting that a significant number of Thai fishing vessels have repeatedly moved their operations, which were shown to include illegal fishing and human trafficking, to evade detection and capture, and that they may now be acting with impunity on the Saya de Malha bank more than 7,000 km from their home port in Thailand.

As we know, seeing is believing, and in collaboration with DigitalGlobe, we have obtained high-resolution satellite images that corroborate Greenpeace’s assertions and reveal just how active the fleet is. Since November, we have documented Thai vessels gathering in one specific location on the Saya de Malha bank for the apparent transfer of fish.

The report, “Turn the Tide: Human Rights Abuse and Illegal Fishing of Thailand’s Overseas Fishing Industry,” outlines the Thai fleet’s exodus: first from their staple fishing grounds in Indonesian waters to a remote region off of Papua New Guinea, then to the Saya de Malha Bank. The evasive moves correspond to the hardline stance against illegal fishing by Indonesia in 2014 that included blowing up illegal vessels, and to subsequent increases in enforcement by Papua New Guinea in August of 2015.

The imagery we’ve captured from Saya de Malha Bank is part of a larger effort to gather high resolution satellite imagery of ocean surface around refrigerated cargo vessels in different parts of the world. With their large carrying capacity, these refrigerated vessels, called “reefers,” collect catch from multiple fishing vessels for transport to shore.

Not only does this type of transshipment allow the fishing fleet to continue working the fishing grounds for months, or even years at a time, but it facilitates the mixing of legal and illegal catch, which is why it is prohibited in many circumstances. What’s more, fishing vessels that remain at sea almost indefinitely have greater potential for abusive labor practices, including the enslavement of crew. The move by the Thai fleet to Saya de Malha almost requires the use of reefers as an efficient way of transporting catch to the home port from such distant fishing grounds.

Using AIS signals from known reefer vessels, we identified precise locations for aiming DigitalGlobe’s satellite sensors. With the knowledge that fishing vessels often don’t broadcast AIS while engaged in illegal activities such as unauthorized transshipment, we were interested in finding out if we could capture suspect vessels using imagery in the vicinity of a reefer.

One of the reefers we chose for imaging, the Thai vessel Leelawadee, seemed a good target. “I saw that it was stopped at the north end of the bank,” says our analyst Bjorn Bergman. “It’s in a location where it may be shallow enough to anchor.” In addition, Bjorn had documented a possible transshipment between the Leelawadee and an unnamed vessel in 2015. That event was documented using AIS data as part of SkyTruth’s assistance with the investigation by the Associated Press into Thai vessels fishing with trafficked and enslaved crews.  It is no surprise that it occurred in the waters of Papua New Guinea.

The first image of Leelawadee on the Saya de Malha bank was captured on Nov 23, 2016. It showed her alongside a refueling vessel, the Mahachai Marine 1.  Refueling at sea, also known as “bunkering,” is another necessity for fishing vessels operating far from their home ports for extended periods of time.

Leelawadee reefer (larger vessel) tied to bunkering vessel Mahachai Marine 1. (DigitalGlobe)

Seven days later, on the November 30, the satellite captured five vessels in one pass: the Leelawadee with two vessels tied alongside her and a vessel tied to the stern of the Mahachai Marine 1 (see images below). Although the three unknown vessels appear to be fishing boats, none were broadcasting AIS signals.

The refrigerated cargo vessel (reefer) Leelawadee with two unidentified likely fishing vessels tied alongside. Captured by DigitalGlobe on November 30, 2016. (DigitalGlobe)

Refueling vessel, Mahachai Marine 1, with unidentified vessel tied astern. (DigitalGlobe)

Since we began our efforts to target imaging satellites on reefers, we have turned up several similar “dark” fleets of fishing vessels in other parts of the Indian Ocean and the Atlantic. Combined with AIS data, we are able to flesh out an even more complete picture of what these vessels are doing. In the case of the Leelawadee, AIS-derived tracks over four years indicate that she has made repeated trips between Thailand and an area inside Papua New Guinea’s exclusive economic zone known as The Dogleg, a poorly monitored, remote region rife with suspected illegal activity. Our data reveals many instances in which vessels have crossed from Indonesian waters into the Dogleg, likely to transship their catch. On July 29, 2015, the Leelawadee rendezvoused for many hours with an unnamed fishing vessel broadcasting an irregular AIS number not tied to a vessel identity.

Then in November 2016, both vessels met again, this time on the Saya de Malha bank. They spent several hours together, indicating a possible transshipment. That rendezvous occurred hours after we captured the photograph of the Leelawadee with two “dark” vessels tied alongside, and right before she left the area on a northeasterly course back to port in Thailand.

Track of the Leelawadee (red) and an unnamed fishing vessel (white) rendezvousing in Papua New Guinea waters in July 2015, then again on the Saya de Malha bank in November 2016.

“That both vessels were seen in the Dogleg, and have now moved to the Saya de Malha Bank provides tangible evidence to support the Greenpeace report” says Bjorn. “And what’s interesting is the pattern is similar to the situation we saw with the AP investigation where these Thai reefers would return again and again to one particular location.” It’s worth noting that the encounter between the Leelawadee and the unnamed vessel that occurred in the Dogleg also followed a transshipment that was photographed in the same location by DigitalGlobe. That photograph led to the capture of the reefer Silver Sea 2, which reportedly had been receiving catch from fishing vessels with enslaved crew.  [Read our earlier post on this investigation.]

2016 – The Good, the Bad, and the Future

2016 has been a very mixed year for the environment. Despite some positive developments for conservation over the past year, there are even greater threats to public and ecological health looming on the horizon. We have a lot of work ahead of us in 2017, but your support can help us continue to hold government and industry accountable in the new year (while giving you a break on your taxes for 2016).

Over the past year, documents came to light proving that federal officials made misleading and unsubstantiated edits to a major report from the Environmental Protection Agency (EPA) on the threats posed by hydraulic fracturing (aka fracking). SkyTruth was among the first in 2015 to specifically identify the inconsistencies in the draft report, but at least the final report more accurately quantifies the extent of known cases of contamination from fracking. However, while low oil and gas prices have slowed some of the push for new fracking and drilling, pipelines have emerged as a new point of contention. The Army Corps of Engineers has delayed approving a river crossing for the controversial Dakota Access Pipeline, but as we wrote this month there are many more pipeline projects underway – all of them posing risks to public safety, clean air, and clean water.

Above: Footage from the 2010 Enbridge Oil Spill into Michigan’s Kalamazoo River.

Off the coast of the United States, President Obama recently withdrew millions of acres of Arctic and Atlantic waters from offshore drilling. This environmental victory is the result of numerous environmental campaigns over many years, including our efforts to document the risks and accidents associated with new drilling. Additionally, President Obama is moving quickly to protect some areas from new offshore oil drilling before Donald Trump takes office in January 2017. We’ve already documented some of Exxon’s drilling activity in Russian Arctic waters (below), but we will have to be even more vigilant if ExxonMobil CEO Rex Tillerson becomes Secretary of State.

Unfortunately, little has changed in the Gulf of Mexico where even after a court settlement negotiated by our partners at the Waterkeeper Alliance, Taylor Energy platform #23051 continues to leak. Taylor Energy, however, is now reneging on their responsibility to contain the ongoing leak, and is suing the federal government to recover $423 million out of $666 million which they were compelled set aside for cleanup and containment.

In July, a federal appeals court again upheld an EPA decision to revoke a massive mountaintop mine expansion permit in Logan County, West Virginia. The EPA decision was supported by scientific studies on the health and environmental impacts of mountaintop removal coal mining, some directly informed by SkyTruth’s satellite derived mountaintop removal footprint data. Yet across Appalachia, Trump and other pro-coal politicians won overwhelmingly on the promise of bringing back coal jobs. These promises likely mean decrease in regulatory oversight and cutting enforcement capability, so we will need satellites and citizen scientists to be even more vigilant.

Donald Trump and supporters at a campaign rally in Charleston, West Virginia. Image Credit: Getty Images

Out at sea, things have been looking up. In partnership with Google and Oceana and with keynote addresses from U.S. Secretary of State John Kerry and actor/ocean advocate Leonardo DiCaprio, we officially launched the first public version of Global Fishing Watch. Our work using satellite data to track suspicious vessel activity on the open ocean has been chronicled in the New York Times Magazine, helped bust a Chinese fleet illegally using drift-nets in the southern Indian Ocean, and prompted the government of Belize to halt seismic testing around a protected reef – sending an oil and gas survey vessel packing. But we can’t do it alone, which is why we are making tools like Global Fishing Watch open to the public for all to use.

On November 9, 2016, the day after the U.S. elections made it clear that we will be facing at least four years of a pro-drilling, pro-mining, anti-regulation Administration, SkyTruth President John Amos wrote:

We believe governments and businesses work better to protect the environment, and to ensure human health and well being, when the consequences of their action and inaction are plain for all to see. Persistent public vigilance has always been necessary for a functioning democracy. It’s especially crucial when governments are disdainful of environmental protection and public health and safety, dismissive of science-based decisionmaking with public participation, and openly hostile toward the public ownership and long-term stewardship of our lands and waters.

This means we need you. We need your support, your engagement, and your vigilance. If you can see it, you can change it.

 

Impact Story: Global Fishing Watch

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Global Fishing Watch is the product of a technology partnership between SkyTruth, Oceana, and Google, designed to enable anyone to see and understand apparent fishing effort worldwide. This, in turn, will help reduce overfishing and illegal fishing and help restore the ocean to sustainability and abundance.

The story of Global Fishing Watch is really the story of a team coming together over the vision of what might be possible with satellite data on a global scale.

More than a decade after its founding, SkyTruth had become known as the small nonprofit with a big-picture view of the world. Environmental organizations had been coming to us for help solving challenging problems with remote sensing. We had become a trusted source for unbiased analysis and indisputable imagery that revealed what was once invisible. So when we were asked to turn our analysis to the issue of commercial fishing far out at sea, it was a natural fit.

In 2012, Pew Charitable Trust’s Global Ocean Legacy program was encouraging conservation in the rich and diverse waters of Easter Island Province, a remote territory of Chile located in the southeastern Pacific Ocean, about 2,500 west of the mainland. Hoping to demonstrate the need for protection and the feasibility of monitoring, they looked to us for a solution.

Satellite photographs of illegal fishing in the area would have easily made the point, but such photos don’t exist. Contrary to common belief, no one is actually taking high resolution, fine-scale images of the entire world at all times. So we had to come up with a new method of looking at fishing behavior far over the horizon.

Using low-resolution satellite radar images, we detected the presence of ships in the water based on the radar reflectivity of their metal hulls. Then we learned to work with radio signals broadcast via the Automatic Identification System (AIS) used by many ships to avoid collisions at sea. Combining the data, our analysis showed that fishing was occurring in the open ocean right up to the edge of Chile’s territorial waters. It also revealed that not all fishing vessels were broadcasting their presence with AIS. That was enough to demonstrate that Chilean waters could be vulnerable to unscrupulous fishing behavior, and the Chilean government subsequently stationed a long-range reconnaissance airplane on Easter Island to monitor activity in the area. With that project, we quickly realized the power of AIS data to identify and track fishing activity over the horizon and out of sight. And that’s where the vision began.

Impact Story: Chevron Spill May Have Reset the Tone for Oil Boom in Brazil

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2011 turned out to be both a banner year for Brazilian oil exploration and a big eye-opener for the people of Brazil. Fueled by the discovery of 19 new oil and gas reserves and hungry for the spoils, big multi-national companies poured billions of new investment dollars into the South American nation.

Most Brazilians expressed little concern over the potential safety risks of the offshore boom. But then SkyTruth president John Amos noticed an inconspicuous report of a seemingly insignificant oil leak buried in the daily cycle of business news.

On November 8, 2011, Reuters reported that Brazil’s oil regulator, the National Petroleum Agency (ANP), was investigating an offshore oil leak near Chevron’s Frade field, 230 miles from the coast of Rio de Janeiro. According to the report, Chevron was checking to see if oil was leaking from a crack in the seafloor.

When John reviewed satellite photos of the area, he saw a slick originating near an exploratory drilling site that extended for 35 miles and covered about 180 square kilometers. By his estimates the sheen on the water represented about 47,000 gallons of oil.

Three days later it had grown to 56 miles in length, and Chevron had declared it a natural seep unrelated to their drilling activities. “It is possible, but call us skeptical,” John posted on our blog. “From my previous years working as an exploration geologist I know there are natural seeps off Brazil. But I’ve never seen a natural seep create a slick this large on a satellite image.” What’s more, comparisons with historical satellite photos showed the slick had not been there before.

Over the following days we watched the spread of oil on the water’s surface. While Chevron maintained that it was natural and estimated a leak rate of 8,400 to 13,860 gallons (200 -330 barrels) per day, John posted satellite images that hinted at a much bigger problem. By his analysis the spill was leaking 157,000 gallons (3,700 barrels) per day. That was more than ten times the official estimate.

John’s reports and the indisputable images he posted gained international media attention,  spurred a vigorous discussion on our site, and led to a public outcry in Brazil.

Unable to hide the true nature of the spill, Chevron came under scrutiny from Brazilian legislators and state agencies, and the tone of their official story began to shift.

Under pressure for more transparency, the oil and gas giant eventually conceded they had lost control of a well. They claimed the pressure of the reservoir had exceeded their expectations and forced oil up through fissures in the seafloor.

Kerick Leite who was working for ANP in offshore inspections at the time reflects on the situation this way: “In my opinion, if were not for SkyTruth’s independent assessment of the spill existence and size, I believe the Chevron Spill would have been dismissed as a minor one,” says Leite, “maybe even a natural seep, as initially reported, and remain mostly unknown by the public even today.”

According to the New York Times, Brazil’s former environment minister, Marina Silva, said “This event is a three-dimensional alert to the problems that may occur.” She told the Times that the spill served as a warning just as Brazil was preparing to expand its oil production and exploit its tremendously rich presalt reserves—an extremely complicated process because the presalt lies in 10,000 feet of water beneath thick layers of sand, salt and rock.

As a result of the spill and Chevron’s misleading response, the ANP banned the company from all drilling activities in Brazil onshore and off, pending a full investigation. After lengthy court battles, the company ended up paying  24 violations, and the company paying $17 million in fines to the ANP, more than $18 million to the Brazilian Ministry of the Environment, and $42 million to settle civil lawsuits.

What’s more, it emphasized how small the playing field is in the deepwater oil and gas drilling industry. As we learned through our Twitter followers, the drilling contractor on the job had been Transocean—the same company involved in the disastrous BP / Deepwater Horizon spill in the Gulf of Mexico just a year earlier. Brazil dodged a bullet with this accident, but the new understanding of how bad it might have been made Brazilians pay attention.

“It was a wake-up call,” said John. “These are multi-national organizations. The same contractors are working for most of the major name-brand oil companies. This kind of thing can happen anywhere.” Chevron’s reluctance to claim culpability and their delayed response to the spill drove home the need for diligence in regulation and enforcement by Brazilian authorities.

Leite said the spill has led to increased public awareness and concern over safety in the oil and gas industry in Brazil that persists today. “I believe the issue of offshore safety now has more priority than before the chevron spill,” he says. “Back when I still worked at the ANP sector dedicated to environmental issues and operational safety, it had around 16 to 18 servants. Today there are around 40 servants dedicated to it.”

It was a full year before Chevron was allowed to resume doing business Brazil. During that time, a significant portion of the company’s global investments remained inaccessible to them. We hope the loss of profits, over and above the fines levied by Brazilian authorities, will provide incentives for Chevron to do a better job and will send a message to other oil and gas companies. Accidents can no longer be hidden or brushed aside. Chevron’s Frade field spill demonstrated that a satellite image can be worth a thousand words — and in this case, millions of dollars.

 

Impact Story: BP Spill — Using Science to Hold BP and Federal Regulators Accountable

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Within a day of the April 20, 2010 explosion on BP’s Deepwater Horizon drill rig in the Gulf of Mexico, we began our high tech surveillance of the spill. Examining satellite images and aerial survey data, SkyTruth quickly became a leading source of independent, unbiased information on the size and scope of the disaster.

It was the largest oil spill in the nation’s history, releasing almost five million barrels of oil into the Gulf of Mexico. As bad as it was, it could have been even worse. Had BP continued to downplay the extent of the disaster, delaying mobilization of the appropriate response, it may have taken even longer than the 87 days it took to cap the well. Our work challenged the official story, spurred government science agencies to get off the sidelines,  and opened a public dialogue about the magnitude of the risk posed by modern offshore drilling..

Throughout the spring and into mid-summer of 2010, as BP’s disabled well continued to pump oil into the Gulf, SkyTruth president John Amos was quoted in hundreds of news reports, and his interpretation and analysis of the raw imagery helped policy makers, the press and the general public make sense of events as they unfolded.

SkyTruth also played a vital watchdog role. One week after the accident, we raised concerns that the amount of oil spilling into the Gulf was likely much higher than the 1,000 barrels-a-day estimated by BP and repeated by government officials. The New York Times and other media outlets picked up the analysis published on the SkyTruth blog on April 27. The next day, government officials publicly broke ranks with BP and raised its estimate to 5,000 barrels a day, the amount we had initially calculated.

John and other independent experts kept the issue in the headlines by presenting new estimates of 20,000 and then 26,500 barrels per day as new images and data became available, leading the public to question whether BP was low-balling the spill rate. On May 4th, the company privately acknowledged the possibility that the well was likely gushing as much as 60,000 barrels of oil a day, 10 times more than the government had previously estimated.  (Later, the government’s scientific teams concluded that the higher estimate was closer to the truth; they estimated that 53,000 barrels were leaking each day immediately before the well was capped on July 15.)

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While NASA and the governments of several foreign countries made their satellite images freely available, without organizations like SkyTruth to interpret those images, the public may have never known the true impact of the spill.

Equally important, we invited people directly into the conversation. Tens of thousands visited our website, blog, Twitter and Facebook pages. During the first ten days of June, for instance, our Blog received more than 70,000 visits – 25,000 in a single day. Meanwhile, our Oil Spill Tracker site, deployed on the fly in the first days of the spill, allowed Gulf residents to act as citizen journalists posting commentary and observations, as well as photos and videos of oil awash on the beaches and petroleum-drenched wildlife.

Oceanographer Ian R. MacDonald, who collaborated with the organization during the three-month Gulf spill and an earlier one in Australia’s Timor Sea in 2009, likens SkyTruth’s mission to that of “a fire truck.”

“When there’s an emergency, SkyTruth is there,” says MacDonald, a professor at Florida State University and one of the world’s foremost experts in remote sensing of oil slicks. “From the beginning of the BP spill to the end, SkyTruth was a public source of very timely raw satellite images and interpreted products, as well as a thoughtful commentary that pulled in the views of other people.”