wv3 accuracy study with histogram

The spark that ignited the PhotoSat accuracy studies

wv3 accuracy study with histogram

2016 PhotoSat WorldView-3 satellite surveying accuracy study, Asmara, Eritrea.

“Everything that the last speaker just told you is wrong”.   This shocked me since I was the last speaker.  I was just rejoining the audience after my presentation at a satellite data distributors’ conference in San Diego in 2008.

I had given a presentation on PhotoSat’s experience using satellite photos for elevation mapping.  I had shown comparisons between PhotoSat stereo IKONOS satellite elevation mapping and hundreds of mining exploration drill  collar elevations.  Our results suggested an IKONOS mapping accuracy of better than 1.0m in elevation.

The speaker who followed me showed the published specifications of the IKONOS satellite.  He declared that this proved that the results I had just shown were impossible. Then he went on to talk about his own stereo IKONOS mapping results.  His results showed 5m to 10m in elevation mapping accuracy.

 

Looking for a way to unambiguously measure our accuracy

The speaker who challenged PhotoSat’s results in the San Diego meeting actually did us a huge favor.  Although it did not feel like that as I sat fuming in my chair.  His comments provided the motivation for me to find a way to prove we were right.  After this meeting we set about looking for a way to unambiguously demonstrate the accuracy of the PhotoSat stereo satellite elevation mapping.

 

Searching for a detailed, high quality, ground survey data set

We concluded that to prove our accuracy we needed to find a highly accurate ground survey data set covering hundreds of square kilometers. But where to find it?

About two months later, a light came on.  I realized that we might find the elevation survey data that we needed from a large, regional, mining exploration gravity survey.  The topographic surveys associated with mining exploration gravity surveys are among the most accurate and carefully checked topographic surveys in the world.

 

An old friend tells me about an existing ground survey data set

I phoned Kevin MacNabb, president of MWH Geo-Surveys International.  Kevin did gravity survey contracts for me when I was a geophysicist at BP.  I said “Kevin, I am looking for a large regional gravity survey with thousands of accurate topographic survey points.  I want to use the topographic survey data to measure the accuracy of PhotoSat’s stereo IKONOS satellite mapping.”

I added “it would be great if the data is in an area of sparse vegetation in a remote region of the world.  This way we can prove the accuracy of our stereo satellite topographic mapping and show that we can do this anywhere in the world.”

Kevin replied “how would 45,000 ground survey points covering over a thousand square kilometers just west of Asmara, Eritrea do?”  For us this was the perfect data set. Eritrea was a challenging place to work.  It had just emerged from a civil war.  A perfect place to be mapping from satellites. For a fuller description, click this link.

 

Eritrea differential GPS survey crew and equiptment

Asmara Project, Eritrea. MWH Geo-Surveys differential GPS survey crew and equipment. Over 45,000 ground points were surveyed between 2004 and 2008. The Magellan RTK base with a ProMarkTM 500 GPS rover are shown in this photo.

 

The Eritea ground survey data is owned by an existing PhotoSat customer

It turned out that Kevin’s customer for the Eritrea gravity survey, Sunridge Gold, was also a PhotoSat customer for stereo IKONOS mapping.  We negotiated the right to use the 45,000 ground survey points for accuracy studies.  In return, we did some additional stereo IKONOS mapping for the company.

 

PhotoSat’s first comprehensive accuracy study

We were immediately able to use 10,000 of the Eritrea ground survey points to measure the elevation accuracy of 200 km² of stereo IKONOS elevation grid.  PhotoSat had already produced this elevation grid for Sunridge Gold.  We measured the accuracy of the PhotoSat elevation grid as 48cm Root Mean Square Error (RMSE).  The full 2008 IKONOS Eritrea Accuracy study is available to review.

 

PhotoSat accuracy measurement and improvement

Since 2008, PhotoSat has been using the 45,000 Eritrea ground survey points as a test bed to measure accuracy improvements in the PhotoSat processing.  This gives us a quantitative measure of accuracy improvements.  We have shown the results in many conferences and published them.  If there are still disbelievers they are certainly not challenging us publicly.

 

Satellite companies start to provide stereo test data over the Eritrea site.

In 2009, two commercial high resolution satellite companies, GeoEye and DigitaGlobe, provided stereo satellite photos over the PhotoSat Eritrea test area.   The DigitalGlobe data was from the 50cm ground resolution WorldView-1 satellite launched in September 18, 2007.  The GeoEye data was from the 50cm ground resolution GeoEye-1 satellite launched on September 6, 2008.

PhotoSat published elevation mapping accuracy reports for both new satellite systems.  The stereo GeoEye-1 PhotoSat elevation grid had an accuracy of 31cm RMSE, determined by 8,893 ground survey points.  The stereo WorldView-1 PhotoSat elevation grid had an accuracy of 35cm RMSE, determined by over 15,000 ground survey points.

 

WorldView-2 joint DigitalGlobe and PhotoSat news release on Eritrea accuracy study

Soon after the commissioning of the WorldView-2 satellite in early 2010 DigitalGlobe asked PhotoSat to use its new processing system to conduct an accuracy study over the Eritrea test area using stereo WorldView-2 photos.  The PhotoSat Eritrea Accuracy study showed WorldView-2 accuracy of better than 30cm RMSE.  These results were issued on March 16, 2010.  The news release is available here.

 

With accuracy improvement PhotoSat mapping becomes PhotoSat surveying

Once the PhotoSat elevation grids achieved an accuracy of better than 30cm many of our customers began using them in place of ground surveying.  We consequently renamed our products that have accuracy better than 30cm to surveying products.

 

The Eritrea ground survey data set has been used for hundreds of PhotoSat accuracy tests and studies

Since PhotoSat first acquired the 45,000 ground survey points in Eritrea, we have used the data for hundreds of accuracy test and studies.

 

2016 PhotoSat Eritrea accuracy studies

In 2016, we used the current version of the PhotoSat Geophysical Processing System to process a full range a stereo satellite photos over the Eritrea test area.  Some of these results are published on our website on the links below.  The link names include the satellite name, the number of ground control points used in the processing and the RMSE accuracy.

 

WorldView-3, Eritrea, 21 GCP, RMSE 15cm

WorldView-2, Eritrea, 21 GCP, RMSE 14cm

WorldView-3, Eritrea, 2 GCP, RMSE 19cm

WorldView-2, Eritrea, 2 GCP, RMSE 19cm

WorldView-1, Eritrea, 21 GCP, RMSE 19cm

WorldView-1, Eritrea, 9 GCP, RMSE 23cm

Pleiades-1B, Eritrea, 74 GCP, RMSE 26cm

Pleiades-1B, Eritrea, 1 GCP, RMSE 28cm

Kompsat-3A, Eritrea, 11 GCP, RMSE 48cm

Kompsat-3A, Eritrea, 1 GCP, RMSE 53cm

ALOS PRISM, Eritrea, 3 GCP, RMSE 1.4m 

SPOT 7, Eritrea, 1 GCP, RMSE 1.4m

ALOS PRISM, Eritrea, 1 GCP, RMSE 2.4m 

 

If you would like more information on PhotoSat surveying you can visit the following links.

Satellite surveying

Mining Industry Applications

Oil and Gas Industry Applications

Case histories

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

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.

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.

 

 

Tailings dyke elevation image number 2.

Monitoring Tailings Dykes with Satellite Elevation Data

In both the oil sands and mining industries, the integrity of tailings dykes is extremely important. Recent tailings incidents demonstrate this. Mapping the tailings dykes and beaches can be challenging with hazardous conditions restricting access for ground surveyors. Using satellite-based elevation mapping allows for data to be collected remotely, with no risk for ground personnel and no permits needed. Regular topographic mapping during construction allows the design engineers to confirm that the dykes are being built to design specifications.

Currently PhotoSat regularly surveys the topography of tailings dykes for the Alberta oil sands mines to an accuracy of 15cm in elevation. In fact, we map the entire tailings systems for Suncor’s Millennium and Steepbank mines about every two weeks. These surveys are used by a wide range of engineers and planners at Suncor. They even did a presentation about their experience comparing different survey options and why they settled on PhotoSat’s technology as their main topographic survey method.

Tailings dyke elevation image

Elevation image of a tailings dyke, December. Red is high, blue is low.

Tailings dyke elevation image number 2.

Elevation image of the same tailings dyke 6 months later. Red is high, blue is low.

Unique Methods for Elevation Mapping

Satellites can collect imagery anywhere in the world, and with new high resolution satellites being launched regularly, there are more options and collection times keep getting faster. Also, PhotoSat has a unique, automatic system for processing stereo satellite imagery to extract the bare-earth elevation values. That’s right – we invented this process ourselves here in Vancouver, and continuously improve the system to get better and better accuracy results. Additional information about the technology we use can be found on the Technology page. And we test our system regularly by publishing accuracy studies that are available on our website here.

We also survey all parts of tailings projects beyond the dykes for a complete profile of a mine site tailings area, including the sand dumps, tailings beaches, and mature fine tailings. The advantage of satellites is that they can collect imagery over a large area in one shot, providing an instantaneous snapshot of the entire tailings beach waterline, the geometry of the beaches, and the height of the tailings dykes. Areas from 100-200 sq km can be collected in one satellite pass.

Our standard elevation accuracy specs for mining projects is better than 30cm, and you can find out more about our digital elevation data package here. If even higher accuracy is required, contact us as we often can provide higher accuracies depending on the project.

To find out more about our engineering grade satellite topography, 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.

Toes and crests, satellite image

Automatic toes & crests mapping at Suncor’s oil sands mine

In this article we’ll look at how the engineers at Suncor have adopted our toes and crests mapping as an integral part of their mine planning process. This is the last post in a 3 part Suncor case study series. In the first post, we discussed Suncor’s comparison of various survey methods, and in the second article we showed how they use satellite elevation mapping for monitoring mature fine tailings.

Mapping of toes and crests is important for monitoring open-pit mining. On the ground, vehicular access, overburden removal and bench integrity needs to be ascertained if the mine is to continue to be profitable and safe. But on the ground is the worst place for surveyors to be: survey teams that examine mine sites directly are exposed to hazards like falling debris and bench wall slumping as well as heavy vehicle traffic. Which is where PhotoSat comes in.

In collaboration with Suncor, PhotoSat has developed a process to automatically map toes and crests to an accuracy of 15cm without survey teams requiring access to hazardous areas of the mine site. Production isn’t interrupted, surveyors are working on tasks that actually require boots on the ground, and accurate mapping of toes and crests allows the engineers to monitor bench integrity and check mine progression against projections.

Toes and crests over a satellite photo

Toes and crests data draped over a satellite photo

 

Toes and crests over PhotoSat’s elevation image

Toes and crests data draped over PhotoSat’s elevation image

 

Bird’s eye view of toes and crests over a mine site

Bird’s eye view of toes and crests data over a mine site

 

Mine planning often takes place on a biweekly or monthly basis, reflecting production speed. We’re able to supply our oil sands clients with useable data within 5 days, meaning analysis of progress and erosion is more granular and data is available in a timely manner.

There are several mine surveying options on the market, many of which Suncor has tried (see our first post for Suncor’s comparison of various surveying methods). Typically these rely on LiDAR, which uses reflected laser light to build images. Terrestrial laser scanning involves survey teams setting up and using multiple scanning stations and consequently requires more time to produce images. And survey teams are still on the ground! Aerial LiDAR avoids this issue but results in huge point clouds that have to be processed before an image is usable, which can take a very long time. GPS survey equipment can also be used, but data paucity and safety remain serious issues.

Using satellites, Photosat offers instantaneous snapshots of all mine site toes and crests derived from our elevation grids. Our proprietary geophysical processing system results in far greater accuracy than conventional satellite mapping processes such as photogrammetry.

Oil sands mines change fast and digital vector data for toes and crests are vital to the engineers for keeping track of what is usually softer rock. Suncor switched over to using PhotoSat’s satellite topography as their main survey method in 2013. While some areas of the mine still use GPS surveying, toe and crest mapping has been carried out exclusively by PhotoSat.

Our elevation mapping is also used for other applications at oil sands and hard rock mines, such as:

  • Sloughing in nonactive areas
  • Pipelines and roads
  • Power poles
  • Buildings and structures
  • In-pit geotech surveying
  • Correcting LiDAR issues

For more information on satellite elevation mapping and toes and crests, feel free to contact us at info@photosat.ca or 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.

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