3D satellite photo showing some of the 775 ground survey points

PhotoSat publishes 21 new satellite surveying accuracy studies

3D satellite photo showing some of the 775 ground survey points

3D WorldView-2 satellite photo of Asmara, Eritrea, showing some of the 775 ground survey points that determine the 14cm PhotoSat surveying accuracy.

21 PhotoSat surveying accuracy studies from seven different stereo satellites

PhotoSat has published 21 new satellite surveying and mapping accuracy studies, now available on our website. The studies include data from seven different stereo satellite systems. The best results show elevation surveying accuracies of better than 15cm.

The accuracy studies include stereo satellite data from the following satellites:

  • WorldView-1
  • WorldView-2
  • WorldView-3
  • Pleiades-1B
  • KOMPSAT-3A
  • SPOT-7
  • ALOS PRISM

 

PhotoSat has measured accuracy on over 750 stereo satellite surveying projects

PhotoSat has delivered over 750 satellite surveying projects since 2007 and we have carried out accuracy evaluations on the majority of them. Most of the survey data on these projects belongs to our customers and cannot be shared publically; however, customers have provided feedback on many of these projects.

The results of these 21 new accuracy studies are consistent with our project accuracy evaluations and customer feedback.

 

PhotoSat accuracy test areas in Eritrea and California

The accuracy studies were conducted over two test areas. One test area is west of Asmara, Eritrea where PhotoSat has access to more than 45,000 ground survey points over a 50km by 20km block.

The second area is in SE California where PhotoSat uses a very accurate Opentopography.org open source LiDAR survey.

 

The effect of different numbers of ground survey points

The studies employed different numbers of ground survey control points for each test area and each satellite system. For some of the satellite stereo pairs the accuracy is significantly improved by increasing the number of ground survey control points.

For example, the WorldView-2 survey for Eritrea is accurate to 19cm in elevation with two ground control survey points, and accurate to 14cm in elevation with 21 ground control points.

In contrast, the accuracy of the WorldView-3 survey for the California test area is not improved by additional ground survey points. This WorldView-3 survey is accurate to 13cm in elevation with one ground survey control point and with 153 ground survey control points.

 

PhotoSat has been continuously producing satellite accuracy studies since 2007

In order to provide objective quantifiable accuracy data for stereo satellite surveying and mapping, PhotoSat has been continuously producing accuracy studies since 2007. We have previously published nine of these studies. The rest of the studies were used for calibrating and improving our processes.

 

21 new accuracy studies all processed with the same version of the PhotoSat processing system

The 21 new accuracy studies were produced with the most recent version (2016) of the PhotoSat processing system. Where possible we used satellite data produced by the 2015 or 2016 versions of the satellite operators’ ground processing systems.

 

Summary of PhotoSat 2016 accuracy study results

Satellite Test area km² GCP RMSE
WorldView-3 California 150 1 13cm
WorldView-3 California 146 153 13cm
WorldView-3 Eritrea 100 21 15cm
WorldView-2 California 173 1 15cm
WorldView-2 California 173 153 12cm
WorldView-2 Eritrea 100 21 14cm
WorldView-1 California 174 153 14cm
WorldView-3 Eritrea 198 2 19cm
WorldView-2 Eritrea 400 2 19cm
WorldView-1 Eritrea 100 21 19cm
WorldView-1 California 174 1 23cm
WorldView-1 Eritrea 420 9 23cm
Kompsat-3A California 144 14 21cm
Pleiades-1B Eritrea 189 74 26cm
Pleiades-1B Eritrea 189 1 28cm
Kompsat-3A California 144 1 50cm
Kompsat-3A Eritrea 130 11 48cm
Kompsat-3A Eritrea 130 1 53cm
SPOT 7 Eritrea 1,458 1 4m
ALOS PRISM Eritrea 2,300 3 2m
ALOS PRISM Eritrea 2,300 1 4m

See PhotoSat’s accuracy studies overview for full details.

For more information about PhotSat’s surveying accuracy, please see our satellite surveying case histories or visit the following links.

Satellite surveying

How can modern satellites photos possibly be accurate to 20 centimeters in 10 kilometers?

By Gerry Mitchell, P.Geo, President PhotoSat

ground control survey points in eritrea test area

3D WorldView-1 satellite view showing the ground survey points in PhotoSat’s Eritrea test area.

 

My intuition rebels at the notion that a satellite orbiting 750 kilometers above the earth, traveling at 7 kilometers per second, could possibly take photos of the ground accurate to 20 centimeters in 10 kilometers. When you take into consideration that these satellites have scanning cameras which take their photos like push brooms, with the north end of the photo taken a few milliseconds before or after the south end, and that the whole satellite is vibrating while the photos are taken, it boggles the mind. It just does not seem that such high accuracy should be possible. However, the satellite photos themselves, checked with tens of thousands of ground survey points, clearly demonstrate that the accuracy is real.

How do the satellites and cameras work?

We engineers and geoscientists in the commercial realm don’t actually know how these satellites and cameras work. Almost all of the technical details of the imaging satellites, their cameras, and their ground processing stations is classified. Or if it’s not classified it’s certainly very difficult to discover. I’ve had many conversations with satellite engineers who seem like they’d love to tell me why their satellites perform so amazingly well. Sadly, they simply aren’t allowed to discuss classified technology with anyone without the proper security clearances.

Whenever I have one of these conversations, it always seems to me that part of what the engineer knows is public and part is classified, but the engineer cannot be sure that he or she can remember what is still classified and what isn’t so it’s safest to say nothing. I’ve had satellite engineers decline to confirm information that is published on their own company’s website. Needless to say, this can make for some very awkward conversations.

We engineers and geoscientists in the commercial world only have access to the satellite photos themselves, and very general public information about the satellites and their cameras.

How accurate are the satellite photos?

When the Digital Globe WorldView-1 (WV1) satellite photos first became commercially available in 2008, PhotoSat acquired stereo photos for a test area in Eritrea where we have over 45,000 precisely surveyed ground points. When we shifted the WV1 photos 3m horizontally to match any survey point, we were amazed to discover that all of the survey points within 10km matched the satellite photos to within 20cm. We eventually documented this discovery in an accuracy study white paper that is now published on our website.

Now, eight years after that initial WorldView-1 accuracy study of the Eritrea test area, we have processed hundreds of satellite photos from the WorldView, Pleiades, SPOT and KOMPSAT satellites and have come to expect this incredible accuracy. I’m still in awe that this is possible and I still don’t know how it is achieved. I do know that the photos are amazingly accurate.

black and white photo of over 15000 ground survey points in PhotoSat Test Area

WorldView-1 satellite photo over the PhotoSat test area in Eritrea. The over 15,000 ground survey points used to confirm that the satellite photo accuracy is better than 20cm in 10km are shown as black dots. The completely black areas are survey points every 20m along lines separated by 100m.

 

 Colour image of a one meter PhotoSat survey grid produced from the WorldView-1 satellite photos

Colour image of a 1m PhotoSat survey grid produced from the WorldView-1 satellite photos. The ground survey points demonstrate that the PhotoSat grid is accurate to 35cm in elevation.

 

 

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.

Seismic survey points

Improve Seismic Survey Planning with Highly Accurate Elevation Models

When planning a seismic survey, petroleum engineers need to know which seismic source points can be accessed safely by vibroseis trucks. Using high detail elevation models generated from satellite imagery, PhotoSat can help.

We use elevation surveying to prepare the groundwork for seismic surveying. Before holes are drilled or vibroseis trucks are on the move, planners know where the likely best spots are. And thanks to PhotoSat’s 30cm accuracy elevation models, they also know where trucks can’t go.

Overturning vibroseis trucks on steep or sudden inclines is a real risk. Planners need more than contour lines: they need high resolution, accurate topographical data to allow them to plan how to best use their vibroseis equipment while keeping their trucks and crews safe. Mapping the ground slope to within 30cm elevation accuracy enables mapping of no-go zones that are too steep for vibrator truck operations, lowering the risk of overturning the vibes on steep inclines. Our clients tell us that this improvement in seismic survey planning helps them reduce project costs and saves time.

Seismic survey points

 

Advance scouting is expensive, risky and time-consuming. And it comes under fire for its environmental impact. PhotoSat’s proprietary geophysical processing system allows us to create usable digital elevation models and precision satellite images within just a few days of a satellite acquisition, with 30cm elevation accuracy and with no boots – or tires – on the ground. The resultant data can then be used for subsequent project engineering and design.

Another advantage of having accurate survey data in the early project stages is the ability to use the elevation models for quality control of the seismic shot and receiver point survey data. In addition, the data is engineering-quality and can be used for all future design and construction work. This reduces survey wait times and allows managers to have increased faith in the reliability of the data.

So how do we get these kinds of accuracies? We have developed our own unique process, and more information can be found on the Technology page. Also, we have published numerous Proof of Accuracy Reports, that compare our elevation data to tens of thousands of independent survey points.

If you’d like to learn more about how PhotoSat built software developed for seismic data processing into a powerful, fast and accurate satellite surveying tool, or find out how that tool can help your project happen, contact us at info@photosat.ca or 1-604-681-9770.

PhotoSat 3d elevation image

Comparison to LiDAR verifies accuracy of WorldView-3 satellite elevation mapping to within 15cm

Back in March this year, we were proud to announce that we’d verified the accuracy of DigitalGlobe’s WorldView-3 (WV3) satellite topography. The digital terrain model PhotoSat produced from DigitalGlobe’s WorldView-3 stereo satellite data was found to be accurate to within 15cm in elevation. Of course, that meant our customers could look forward to unprecedented accuracy from us, with an accuracy study to back it up. Here’s the original piece from PRNewswire:

 3d elevation image

PhotoSat 3d elevation image from WorldView-3 satellite data of the Garlock Fault in California

Engineers to benefit from high quality elevation products

VANCOUVER, March 25, 2015 /PRNewswire/ – PhotoSat is pleased to announce that the elevation data processed from DigitalGlobe’s new 30 centimeter resolution satellite, WorldView-3, has been verified as accurate to within 15 centimeters. DigitalGlobe is a leading global provider of commercial high-resolution earth imagery products and services, and is the first company to offer 30 cm resolution satellite imagery commercially.

For the study, PhotoSat produced a 50 cm grid of elevations using its proprietary geophysical processing technology with stereo satellite images taken by WorldView-3. The resulting elevations were then compared to a 50 cm LiDAR elevation grid in Southeast California, accurate to approximately 5 cm in elevation and available on the OpenTopography website. The size of the comparison area was 88 square kilometers. The resulting 15 cm RMSE elevation accuracy was impressively achieved using a single ground reference point. The full WorldView-3 accuracy study is available on the PhotoSat website at www.photosat.ca/pdf/garlock-30cm-wv3-elevation-accuracy-report-mar2015.pdf.

PhotoSat’s highly accurate elevation grids have been used for years by oil and gas and mining engineers as a cost-effective alternative to ground surveying and airborne LiDAR mapping. The satellite imagery from WorldView-3 will allow PhotoSat to deliver the highest quality topographic data yet.

“The DigitalGlobe WorldView-3 satellite data is the highest quality satellite photo data that PhotoSat has ever processed,” said Gerry Mitchell, President of PhotoSat. “In this test, an elevation grid extracted from stereo WorldView-3 satellite photos matches a highly accurate LiDAR elevation grid to better than 15 cm in elevation. This result takes satellite elevation mapping into the engineering design and construction markets and directly competes with LiDAR and high resolution air photo mapping for applications like flood plain monitoring.”

“The fact that PhotoSat has validated our elevation data to within 15 cm is amazing and even exceeds our initial expectations,” saidKenyon Waugh, DigitalGlobe’s senior director of vertical segment products. “With these elevation products, customers in the oil, gas, and mining sectors can leverage our truly global reach and realize cost savings on the order of 50 percent.”

LiDAR and satellite elevation data

LiDAR grid compared to PhotoSat’s WV3 grid. Comparison of the LiDAR and WV3 elevation grids for a 1000m wide area. Minor differences between the elevation grids are visible.

 

About PhotoSat

PhotoSat has invented a new technology that generates the world’s most accurate satellite topographic mapping.  This engineering quality data shortens timelines and eliminates surveying delays in all phases of resource and engineering projects. We have delivered over 500 highly accurate elevation mapping projects, and have published a number of accuracy studies which are available on our website. For more information please visit www.photosat.ca.

About DigitalGlobe

DigitalGlobe is a leading provider of commercial high-resolution earth observation and advanced geospatial solutions that help decision makers better understand our changing planet in order to save lives, resources and time. Sourced from the world’s leading constellation, our imagery solutions deliver unmatched coverage and capacity to meet our customers’ most demanding mission requirements. For more information, visit www.digitalglobe.com.

To find out more, either visit us at  www.photosat.ca, view the original accuracy report here or contact us at info@photosat.ca.

Surface topography image and pipeline routes

Surface topography and pipeline route selection

Oil and gas pipeline routes are absolutely pivotal information. The route that a line has to take is always a trade-off between what you’d ideally like to have and what you have to accept: an ideal oil pipeline would run in a trench across a totally flat surface with constant temperature and no seismic activity. In real life, we have mountains, deserts, heat and cold fluctuations, seismic activity of all sorts, permafrost or rocky outcrops that necessitate raising the line on supports, and other obstacles. (And that’s without mentioning regulatory environment…)

On the one hand, knowing the terrain you have to get across lets you know what kind of pipeline you can have. On the other, knowing the pipeline plans lets you know what kind of geotechnical data you’re going to need to bring it home safely and efficiently.

When you’re researching pipeline route corridor alternatives, you’re equally faced with compromises. You need reliable, accurate surface topography data for the whole potential route corridor. Solid geotechnical data allows correct pipeline route selection and implementation, but getting it by traditional means is costly, time-consuming and environmentally damaging and can run the risk of damaging your local reputation.

Surface topography image and pipeline routes

PhotoSat elevation image and pipeline route options

 

PhotoSat’s highly accurate, engineering-quality digital surface topography allows you to examine and select multiple pipeline corridors and plan final routes, based on elevation data accurate to 30cm vertically. You can do it without risking survey teams in inaccessible locations or hostile environments. Usable engineering survey data is generated fast, typically within five days. We’ll typically supply our oil and gas clients with an engineering quality 1m topographic grid accurate to 30cm in elevation, 50cm or 1m contours, and a 50cm satellite ortho photo. And after it’s been used to select pipeline routes, the surface topography can be used for all phases of the project, because it’s accurate and comprehensive enough for most engineering tasks.

The accuracy of our surface topography has been proven in many accuracy studies using tens of thousands of ground survey points for comparison. View our proof of accuracy reports for more information. We have completed over 500 projects all over the world.

To learn more about our revolutionary satellite image processing system, or to find out how it could facilitate your oil and gas project, contact us at info@photosat.ca or 1-604-681-9770.

LiDAR and satellite elevation data

PhotoSat verifies accuracy of DigitalGlobe’s 30cm WorldView-3 satellite elevation data to within 15cm

PhotoSat has recently completed a study to measure the accuracy of the elevation grid produced from the new 30cm resolution WorldView-3 (WV3) satellite. We measured the accuracy of our topographic mapping by comparing it to a highly accurate LiDAR elevation grid. The study was carried out over an 88 km2 area in Southeast California that overlaps an Open Topography LiDAR survey.

Read the full elevation accuracy report here (PDF)

For the study, PhotoSat produced a 50cm grid of elevations using our proprietary geophysical processing technology with stereo satellite images taken by WV3. Our resulting elevations were then compared to a 50cm LiDAR elevation grid, which is accurate to about 5cm. The resulting 15cm RMSE elevation accuracy was impressively achieved using a single ground reference point.

Below are some images of the elevation surveys and the differences between the datasets. You can also view the full WorldView-3 elevation accuracy study (PDF) on our website.

For more information on our highly accurate satellite topography, contact us at info@photosat.ca or 1-604-681-9770.

WV3 30cm resolution satellite ortho photo
Figure 1: WV3 30cm resolution satellite ortho photo created from WV3 stereo photos, for the area of the LiDAR survey used in this study.

LiDAR elevation grid
Figure 2: An image showing a portion of the LiDAR elevation grid. Lower elevations are blue, and higher elevations are red.

PhotoSat’s WV3 elevation grid image
Figure 3: PhotoSat’s WV3 elevation grid image covering the area of the LiDAR image. The grid has an elevation point every 50cm. At this scale, the LiDAR and WV3 images are identical. Lower elevations are blue, and higher elevations are red.

PhotoSat’s WV3 elevation grid clipped to the LiDAR extents
Figure 4: PhotoSat’s WV3 elevation grid clipped to the LiDAR extents, for areas with slopes less than 20% grade. Areas where development occurred since the 2008 LiDAR survey were removed for the accuracy analysis.

Differences between our WV3 elevation grid and the LiDAR elevation grid
Figure 5: The differences between our WV3 elevation grid and the LiDAR elevation grid, for areas with slopes less than 20% grade, are shown in a standard histogram on the left and a cumulative histogram on the right. If we assume that the LiDAR is perfect, the WV3 elevations have a Root Mean Square Error (RMSE) of 15cm. Ninety percent of the WV3 elevations are within 22cm of the LiDAR elevations giving a 90% Linear Error (LE90) of 22cm.

Comparison of the LiDAR and WV3 elevation grids for 1000m wide area
Figure 6: Comparison of the LiDAR and WV3 elevation grids for 1000m wide area. Minor differences between the elevation grids are visible at this scale.

Continue reading PhotoSat verifies accuracy of DigitalGlobe’s 30cm WorldView-3 satellite elevation data to within 15cm