Satellite survey of Libya with ground survey points

Are PhotoSat satellite surveys really more reliable than ground surveys?

By Gerry Mitchell, P.Geo, President PhotoSat

Satellite survey of Libya with ground survey points

World View 2 satellite survey in Libya with ground survey points for 3D oil and gas seismic survey.

 

In 2008, I would get a hollow feeling in the pit of my stomach whenever customers phoned or emailed to tell us that the PhotoSat surveys did not match their ground surveys. Back then, I was sure there was a problem with the satellite photos, or that we had made some terrible mistake in our processing.

However, by 2013 our customers were using PhotoSat satellite surveys to check and adjust their ground surveys.

Ground surveys right, PhotoSat surveys wrong?

Back in 2008 it was clear to everyone, including me, that ground survey data was right and satellite survey data wrong. After all, ground survey data was collected by someone who had stood on the ground. It was the “ground truth”.

In comparison, the PhotoSat surveys were produced from satellite photos taken from 750 kilometers above the earth. Of course the ground surveys were right and the satellite photo surveys were wrong. Or so we thought. As we did more and more satellite surveying projects, we began finding obvious ground survey errors. Some of these projects had thousands of ground survey points.

ground target at mining project drill hole

Ground target at a mining project drill hole with arms 20cm wide and 1m long. The image to the right show how this target appears on a 50cm ground resolution GeoEye satellite photo.

 

Some ground surveys wrong, PhotoSat right

We began finding projects with two sets of ground survey data, one set matching the PhotoSat surveying perfectly and the other set mismatching. Investigating these cases with customers was eye-opening and often entertaining.

On one project in southern Mexico, all of the ground survey points on or near roads matched the PhotoSat surveying perfectly. The points in remote areas, particularly on the tops of hills, had differences of two to five meters in elevation.

So what happened? The contract surveyor had used his high quality, bulky, GPS surveying equipment for the survey points that he could drive to. But he had sent his young assistant with a hiker’s GPS to all of the survey points on the hilltops. The surveyor was confident that the client would never check those remote points.

By 2010, we had become much more confident in the accuracy and reliability of our PhotoSat surveying. When there was a mismatch between PhotoSat surveying and ground GPS surveying we began suggesting that the PhotoSat surveying was “usually right”.  As you can well imagine, many of our customers, and all of their surveyors, were sure that I was delusional.

We had to find another strategy. We began saying, “Thanks for telling us about our mistake. Please send us a copy of your survey data and we will see if we can identify and fix our problem”.

Drill hole with 40cm by 40cm white concrete block

Drill hole with a 40cm by 40cm white concrete block on a mining project in central Mexico. The drill holes on this project were surveyed three times by three different GPS survey contractors. The coordinates of this drill hole on the three surveys are shown on an extreme zoom of the PhotoSat WorldView satellite survey. The PhotoSat survey has more reliable coordinates than any of the 3 GPS surveys.

 

Not all GPS surveys created equal

We also learned that not all ground GPS surveys are created equal. All good quality GPS systems record the GPS signals for later processing, so we began asking for copies of these GPS recordings along with the GPS ground survey coordinates.

The effect of this simple request on the quality of the survey data was remarkable. Some surveyors would immediately go and resurvey the ground points as soon as we asked for the GPS recordings.

By processing the GPS recordings we could see how long the surveyors had been at each point. In many of the significant mismatches, we discovered that the GPS recording times were much too short for ten centimeter accuracy. At first we had pushback from many surveyors when we suggested that their coordinates were probably inaccurate.

Then in June, 2011, the International Association of Oil and Gas producers published a thick report of guidelines for GPS surveying, freely available as a PDF file. For us this was a godsend.

Whenever there was debate about GPS accuracy, we would email a copy of the report saying, “These are the guidelines that we are relying on.  Please tell us where they are wrong”. All the discussions about recording times for GPS accuracy stopped.

Most ground surveys are good quality

Of course, it’s worth noting that most of the ground surveys that we receive are very good. Only occasionally are there serious problems that we cannot easily resolve. And of course PhotoSat also makes occasional processing errors and mistakes.

We always investigate whenever the PhotoSat surveying does not match the ground surveying. When we find it to be our mistake, we fix the PhotoSat survey data and resend it to the customer at no cost.

Correcting multiple mismatching ground surveys

By 2013, many of our repeat customers no longer assumed that the PhotoSat surveys were wrong when they did not match their ground surveys. In just five years there had been a 180 degree shift. In 2008, ground surveying always proved that PhotoSat surveying was wrong. By 2013 the PhotoSat surveying was being used to quality check and fix ground surveying.

This is great for projects with several different ground surveys. These are often surveyed by different contractors. For example, we have one case of an oil and gas project with five different ground GPS surveys performed by five different contractors. We proved that none of the ground surveys matched any of the other four ground surveys.

The key ground survey was for an oil well that discovered several hundred million barrels of oil. We matched the PhotoSat survey to the discovery well. All of the other four surveys mismatched the PhotoSat survey, each by different horizontal and vertical distances.

We used the PhotoSat survey to measure the offsets of each of the ground surveys from the oil well. Then we adjusted the other four surveys to match the oil well. This gave the project a consistent set of ground surveys all matched to the oil well.

This case history is described in more detail here.

Give GPS surveys on an oil and gas poject

Five GPS surveys on an oil and gas project. Each was done by a different survey contractor. None of the surveys matched each other. PhotoSat detected the mismatches and adjusted the survey data to produce a coherent survey data set.

 

Please see the experience section of the PhotoSat website for additional case histories and accuracy studies.

geologic formations in northern iraq

The accidental discovery of a new way to produce accurate elevation surveys from satellite photos

By Gerry Mitchell, P.Geo, President, PhotoSat

geologic formations in northern iraq

3D WorldView-2 image looking along dipping geologic formations in Northern Iraq. Produced by PhotoSat.

In an effort to find a faster way to produce elevation surveys from satellite photos, PhotoSat geophysicist Michael Ehling and I accidentally discovered a novel way to greatly improve the accuracy and resolution of satellite topographic survey results.

It was 2007, during the peak of the natural resource boom and PhotoSat could not keep up with the demand from Vancouver mining companies who needed accurate satellite survey data for their projects in remote parts of the globe. Without accurate ground surface surveys the mining engineers couldn’t produce reports of ore body volumes. Without the engineering reports the companies couldn’t report their mining discoveries to a booming stock market waiting expectantly for their news.

Interactive photogrammetric processes

Michael and I had been watching how photogrammeters produced elevation surveys from stereo satellite photos since 2004, when stereo IKONOS satellite photos first became available. PhotoSat was buying stereo IKONOS satellite photos from Space Imaging, now part of DigitalGlobe.

We were reformatting the photos so that the photogrammeters could produce elevation surveys using computer systems that had been designed for processing stereo photos taken from airplanes. They were using highly interactive processes and were taking an average of 150 hours to produce satellite surveys for 100 square kilometer projects.

Automatic matching

Michael and I could see that the processors spent most of their time interactively measuring the matches between identical features on pairs of satellite photos. The photos had been taken with the satellite looking at the same area on the ground from different directions. By identifying identical ground features on each of the photos, and precisely measuring their locations, the elevations of the features can be computed.

When Michael and I asked if the photo feature matching could be done automatically we were told that the automatic process usually didn’t work, but when it did, editing the results took more time than doing the matching interactively, so no one used it. As geophysicists we were intrigued by what looked like an interesting technical challenge.

Oil and gas seismic processing tool box

In the 1980’s and 90’s when I was working as a Geophysicist in oil and gas exploration I processed a lot of seismic data. Oil and gas seismic survey data is used to image geological formations thousands of meters below ground in the search for oil and gas. Seismic data processing has always been one of the most complex and computer intensive data processing fields, with expenditures of billions of dollars annually.

Over the past 50 years seismic processors have developed an immense array of data processing tools, including many automatic image matching tools, and I thought that we could probably apply these to the satellite photos.

Gerry and Michael at the siesmic workstation

Oil and Gas seismic processing and interpretation workstation. Gerry Mitchell on the left and Michael Ehling on the right. This technology was the inspiration for the PhotoSat satellite processing system.

Michael tested seismic processing image matching tools on stereo IKONOS satellite photos for several months in 2007. He had to format the digital satellite photos so that they would look like seismic data to the seismic processing systems, run tests, and then reformat the results to look like photos again.

We were in search of a faster way to produce the survey results that the photogrammeters were spending hundreds of hours to produce. We were testing with a pair of IKONOS satellite photos that had already been processed by the photogrammeters so that we could compare our results with theirs.

Gerry, Michael and Jayda at workstation

Michael, Jayda and Gerry using the PhotoSat Workstation on a satellite surveying project.

Initial PhotoSat processing test results were amazing

After three months of testing we had our first real success. We were astounded by the results. We could see many fine topographic details on our test data that were simply not visible at all in the photogrammetric processing.

We continued to refine the process over the next few months until we had produced satellite survey results that were over three times as accurate as the photogrammetric processing and had much more topographic detail. The initial process took over 100 hours of computer processing time to process 100 square kilometers, so we had not really found a faster way to produce the results, but completely unexpectedly, we had found a way to produce better results.

comparision of photosat survey

Satellite survey of a river valley processed by conventional photogrammetric methods on the left and by PhotoSat processing on the right. The PhotoSat surveying shows fine topographic detail on the river flood plain that has no expression on the conventional processing.

New PhotoSat Workstation built from scratch

Now, nine years after our initial accidental discovery we still have a team of researchers and software engineers improving our satellite processing system.

Several years ago they replaced the seismic processing system with a computer system built from scratch to efficiently apply the seismic algorithms and processes to satellite photos. This system, the PhotoSat Workstation, was designed to harness the processing power and speed of Graphics Processing Units (GPUs). The GPUs process numerical data a thousand times faster than CPUs. Older software that is retrofitted to use GPUs typically shows speed improvements of two to five times.

It took several years and several million dollars of software development, but since our initial discovery in 2007 we have successfully created an automatic process that produces satellite surveys much faster than the photogrammeters, with much higher accuracy and better topographic detail.

Measure Twice, Cut Once: The Importance of Satellite Surveying in Mine Site Planning and Construction

Oil sands elevation map with 50cm contours

Tailings elevation map with 50cm contours

Keeping a mine safe, profitable and compliant with legislation means frequent, accurate surveying. Planning begins with exploration and identification of likely sites, and particularly in oil and gas projects this can result in delays and false starts. Traditional methods of identifying potential sites suffer from major shortfalls, including the challenges of surveying large areas with traditional methods. The gap between geologists’ opinions and test drilling with a high likelihood of success has never been adequately filled, resulting in continuing requirements for multiple overlapping exploration techniques including exploratory drilling and ground-based surveying.

Mine site planning and construction has surveying needs that no other project matches. Like any engineering project mine site construction requires accurate surveying, but few other large engineering projects are built in hostile, difficult to reach terrain. And few others change so much or so fast. The fundamental fact about a mine is that it is dynamic – it alters the landscape and has to change itself too. That’s true of deep underground mining, open cast, leach mining and every other kind of mine operation.

Surveying Challenges

This presents surveying challenges. Mine sites are typically more remote than other engineering sites: the typical engineering project expands or connects to some built environment, while mines are usually in isolated places far from cities and infrastructure, meaning that they often require their own infrastructure. They’re often in rugged terrain too, or in climatic conditions that make surveying more difficult, such as the mountains of Argentina, the Australian outback, or the Arctic.

All of this means that mine surveying often can’t be done well with traditional tools. Even using modern on-the-ground tools like LiDAR and GPS, survey teams still need to travel to inhospitable terrain and map the site in weather that can range from uncomfortable to downright dangerous.

Then there’s the issue of changes to the mine site. While many of these occur underground in tunnel mines, even these produce significant amounts of waste rock. And larger open pit mines produce both overburden and (usually) tailings which must be monitored. Neither GPS nor LiDAR is usually fast enough to provide mine operators with monthly updates that allow monitoring and ongoing tailings planning and control. This is going to become a bigger issue over the next couple of years, post-Brazil.

So what about drones? Drone technology is in its infancy, so it’s likely to improve. Camera-carrying, real-time streaming drones are available to consumers for almost pocket-money prices; professional models can fly for hours and provide images of remote areas without risking human operators. Surely they can offer a solution?

Drones can do that. But they’re dependent on weather: just as much as larger aircraft, they can’t fly in high winds or see through clouds. They also require an on-site operator. Drones can do things a survey team can’t, like overflying tailings ponds, and they’re increasingly being offered as a solution to a mining industry that has more need for accurate, timely surveying than ever before – and less spare cash than before to spend on it. But they can’t provide the consistency and climate resistance that some mines require.

So far we’ve talked about surveying itself: gathering data. But the majority of data gathered, whether by ground or airborne LiDAR, GPS, drone overfly, or any other method, is just that: data, not information. Translating it into 3D models that resemble what’s happening on the ground and tells observers something they didn’t already know is a time-consuming, computer power-eating process. The acquisition and processing speeds, taken together, simply don’t match up to the pace of decision making that modern mining requires.

Satellite Surveying to the Rescue

All, that is, apart from satellite mapping. Satellites are unaffected by remoteness and inhospitable terrain. They’re definitely out of danger; whole mine sites can be imaged from space in one shot, including those areas where it would simply be impossible to send a survey team. And the accuracy of PhotoSat’s satellite elevation data is unparallelled: we deliver 30cm accuracy for mine site mapping, for instance.

More telling yet is the availability of the information. In contrast to processing times measured in weeks, PhotoSat uses a proprietary technology based on seismic survey data processing tools to drastically cut the time between data acquisition and final deliverables. For example, we map one of Suncor’s mine sites biweekly and deliver within just five days in order to meet their planning meeting deadlines.

PhotoSat’s proprietary image processing tech can be adapted to specific client needs too. For instance, our contract with Suncor involves using a mixture of high and low resolution elevation grids, depending on where the imagery is used and taken. We use high resolution data to map Suncor’s mature fine tailings pond, overburden dump, and mine pit advance to an accuracy of 15cm elevation or more. One result of this approach is that the same images can be used by multiple departments – PhotoSat derived images are passed along to Suncor’s Tailings Engineers, Geotechs and Production Planning departments.

Well sites in Alberta

Well sites in Alberta

During an unrelated project for producing SAGD well sites in Alberta, PhotoSat was able to identify 70 well sites, resulting in a total project cost of $12,000 – just $170 per well – during a project that lasted from initiation on January 30, 2015 through image acquisition on February 4th to processing completion on February 6, 2015. The accuracy of the well head locations we provided were within 11cm RMSE, as compared to Government of Alberta certified RTK surveying. We were able to provide 50cm contours and a 1m elevation grid over potential well pad areas without needing exploratory drilling, and without a single boot on the ground or drone in the air.

To learn more about PhotoSat’s revolutionary satellite topography system and what it can do for your business, contact us at info@photosat.ca or 604-681-9770.

Suncor mature fine tailings

Canadian Mining Association Adopts New Tailings Recommendations

The Canadian Mining Association has agreed to implement a new set of guidelines aimed at improving tailings storage practices. In the wake of the Mount Polley incident, Canada’s principal mining industry group has agreed to adopt a raft of new waste management policies.

Tailings have been in the news recently following several major spillages, and the industry is responding by tightening up codes of practice to ensure better waste management becomes the norm.

Following Mount Polley, when mining waste was accidentally released into Canadian lakes and rivers, an independent review was commissioned by the B.C. government. The Chief Inspector of Mines weighed in, finding that geological features under the dam including a layer of clay weren’t taken into account at the design stage. The CIM found that while mining operations there didn’t break any laws or regulations, they didn’t meet best practices either. In response, the Energy and Mines Minister Bill Bennet announced in 2014, the government planned new regulations that would make British Columbia a world leader in tailings storage.

The government-commissioned review, completed in January last year, recommended that all mining companies operating in the region should abide by the MAC’s code of best practice: in response the MAC organized its own independent review, seeking to improve that code.

The raft of 29 recommendations will extend tailings policy in both directions – up and in, to the heart of mining companies with tailings ponds or storage, and out to the communities nearby. MAC chief executive officer Pierre Gratton said in December, ‘Everyone of these recommendations, if it’s going to reduce the incidents, we want to implement as quickly as possible.’

Communities who may be affected by tailings incidents are to be involved in accident response planning and training, reflecting increased recognition within the industry of local communities as stakeholders in the industry. Meanwhile responsibility for signing off on tailings measures will be taken into the C-suite, effectively making the core of the company responsible for tailings.

Other measures recommended by the government review include the phased introduction of Best available Technologies, an increased role for tailings review boards and expanded corporate design commitments.

Satellite Surveying for Improved Tailings Monitoring

PhotoSat has extensive experience mapping tailings areas to help improve monitoring and management. We have been providing 20cm accuracy satellite surveying for Suncor’s Millennium Mine about twice a month since 2013, after they compared our mapping to alternative methods. The engineers at Suncor use our elevation data (DEM) for most of the mapping and surveying of their Tailings Reduction Operation. They also use it to help reduce their Mature Fine Tailings inventory.

Satellite ortho photo and PhotoSat elevation image of Suncor’s mature fine tailings

Suncor mature fine tailings

© DigitalGlobe 2014

 

In addition, Golder Associates uses our elevation models for satellite monitoring of the Penasquito Tailings Storage Facility. They presented their results at the Tailings & Mine Waste Conference in Vancouver in October 2015.

To find out more about using our high accuracy elevation models for tailings operations, contact us at info@photosat.ca, or 604-681-9770.

 

50cm satellite ortho photo

Alberta to Ease Tailings Regulations

Alberta has announced that it is easing up on tailings regulations, as several mine operators in the region are asking for reduced regulatory pressure. It’s a move away from the regulations, known as Directive 74, that have governed Alberta oil sands for the last six years.

Directive 74 required mining companies to ‘reduce tailings and provide target dates for closure and reclamation of ponds,’ and to report to the industry watchdog on their progress. But the industry has failed to meet the requirements of the legislation – and the Energy Resources Conservation Board (ERCB) watchdog stopped enforcing them in 2013, the last time a company was punished for not hitting its cleanup targets.

Parker Hogan, a spokesman for Kyle Fawcett, the Alberta Environment and Sustainable Resource Development Minister, said, ‘What we have heard is that despite the best efforts and significant investments, companies have had significant challenges to achieve the requirements that are in Directive 74.’

Since then, the ERCB has been replaced by a new regulatory body, the Alberta Energy Regulator (AER), and Directive 74 has been replaced by the Tailings Management Framework (TMF), a new regulatory structure with different aims. (The new framework is accompanied by strict groundwater use rules.)

The key change has been to refocus efforts on growing industry sustainably rather than directly on reducing tailings ponds. The new regulations give industry more leeway in some areas, allowing them to slow the growth of tailings ponds rather than working to actually reduce them; but they also promise new restrictions in other areas.

Kyle Fawcett laid out in more detail the requirements of TMF:

  • limit the amount of tailings that can be accumulated,
  • push companies to invest in technology to reduce tailings
  • establish thresholds to identify when companies must act to prevent harm to the environment
  • require companies to post financial security to deal with potential remediation issues and
  • ensure tailings are treated and reclaimed throughout the life of the project and are ready to reclaim within 10 years of the end-of-mine-life of that project.

Hogan said, ‘this is a shift towards the management of tailings in a way that respects the needs to mobilize new technologies and harness innovation so we can manage this size and scale of environmental impacts to a point we can move away and into reclamation.’ Directive 74 may have been abandoned, but the long-term goals that informed it are still in place.

So what does that mean for mining in Alberta? Are things getting easier or tighter? Overall, the new regulations are mining-friendly. They’re designed to facilitate industry expansion without making unacceptable environmental sacrifices. And that means they’re more long-term, but also that there’s a missing piece of the puzzle: for TMF to come together, new technology that isn’t online yet will be needed. Kyle Fawcett points out: ‘Technology unlocked the oilsands. It will be key to finding the long-term, effective solutions to tailings ponds management.’

Some of that new technology, though, is in place. PhotoSat has extensive experience working with players in the oil sands sector: while oil sands companies seek to accelerate tailings reclamation, reduce the need to build more tailings ponds and reduce their inventories of mature fine tailings, they struggle to do it without accurate, up-to-date survey data. Scanning tailings areas with GPS or ground-based LiDAR comes with a host of problems, including team safety.

50cm resolution satellite ortho photo

50cm satellite ortho photo

© DigitalGlobe 2014

 

1m PhotoSat elevation image (accurate to better than 15cm in elevation)

1m PhotoSat elevation image

1m contours (accurate to better than 15cm in elevation)

1m contours

 

By comparison, PhotoSat’s unique satellite surveying technology, facilitated by software that builds on seismic data processing tools, produces highly accurate elevation data faster, with better definition of steep slopes and without subjecting survey crews to risky environments. It’s a process that’s used to safely survey Suncor’s TRO (Tailings Reduction Operation) in Alberta. PhotoSat has mapped their tailings site twice monthly since 2013, as well as producing automated toes and crests. Many oil sands and other types of mines have adopted PhotoSat mapping to improve tailings monitoring and measurement.

To learn more about our topographic processing system, or to find out how it could facilitate your resource project, contact us at info@photosat.ca or 1-604-681-9770.

A comparison of survey methods for Suncor’s oil sands mine

At the Trimble Dimensions conference in 2014 Suncor and PhotoSat presented the results of Suncor’s use of our satellite surveying for their Tailings Reduction Operation (TRO) at their oil sands mine in Northern Alberta. The mapping area is about 271 km2.

The full conference presentation PDF can be seen here.

suncor tailings areas

Suncor’s tailings: 50cm WorldView satellite photo                                         1m elevation image

 

In 2012, Suncor’s survey department was given the challenge to do monthly topographic surveys of all TRO cells. They tried surveying with GPS equipment, however less than 20% of the area was safely accessible by ground crews. Suncor also tried 3D scanners but found them very slow, requiring multiple set-ups and the data was sparse. They had previously tried airborne LiDAR but found the point clouds to be prohibitively large, and the data delivery to be frustratingly slow.

In 2013, the engineers at Suncor knew they were in need of a surveying method that would have high accuracy, fast delivery, and improve safety for field crews. PhotoSat stepped in to produce engineering quality elevation mapping from satellite photos quickly and safely. Stereo satellite photos were collected over the mine site, providing a snapshot of the entire site every two weeks. Highly accurate elevation data was then produced from the stereo photos using our unique geophysical processing technology.

We provided Suncor’s team with the satellite survey data within 5 days of the satellite photo acquisition to use at their biweekly planning meetings.

Elevation image differences

Elevation image: January 20                                                           Elevation image: February 23

Many features visible in the January 20 topography were buried by tailings by February 23.

Oil sands sand dump with contours

50cm tailings lift thickness contours: Jan 20 to Feb 23

 

During the presentation, Suncor also discussed the advantages of the customization available with our data. For example, PhotoSat provides Suncor with data in their local mine grid coordinate system. Also, we provided a ‘thinned’ version of the elevation grid, which reduces the density of point clouds in flat areas without degrading the quality and accuracy.

Taking all this into account, since 2013 Suncor has switched to satellite surveying as their main surveying method for their TRO Operation. We have been surveying this area about every 2 weeks since 2013, and continue to at the time of this post.

 

Suncor still uses GPS equipment for surveys of some areas of the mine, but for all the non accessible areas PhotoSat’s satellite mapping is the preferred method. The high resolution elevation data is also used for the tailings pond beaches, as well as mine pit advance and overburden dumps. One of the great features is that the satellite surveying is used by a variety of groups, including Tailings Engineers, Geotechs, and Production Planning.

For the full story, view or download the conference presentation PDF here.

In later posts we’ll look at how Suncor has adopted satellite surveying for mapping mature fine tailings cells, as well as mine site toes and crests.

If you have any questions feel free to contact us at 604-681-9770 or info@photosat.ca.