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.

Case study: Reducing Suncor’s mature fine tailings inventory

This post is part 2 in a series looking at how Suncor uses our topographic survey data to  assist their Tailings Reduction Operation (TRO). In this post we’ll look at how they use the data to measure the thickness of their mature fine tailings (MFT) dewatering cells.

Background on mature fine tailings

Mature fine tailings are the clays from the bitumen ore that are suspended in the tailings water. To reduce the area and volume of oil sands tailings ponds, tailings water with suspended clay is mixed with a flocculent which causes the clay to settle out. The tailings water is pumped into dewatering cells where clear water drains off for reuse in bitumen processing while the clay is left behind.

PhotoSat has developed a process to measure the thickness of the clay in each of the mature fine tailings cells in thickness intervals of 15cm. We use our highly accurate topographic mapping between two satellite photo dates to create the detailed elevation maps.

Suncor’s MFT designated drying areas:

  • Total surface area 7.5M m2 (1,866 acres)
  • 697 tailings cells
  • 2788 discharge locations
Suncor mature fine tailings areas

Suncor mature fine tailings areas

 

Zoom of MFT designated drying areas

Zoom of MFT designated drying areas

 

How it works

In last week’s post, we saw that Suncor compared our satellite topographic surveys to other survey methods, and has switched to using PhotoSat mapping as their main surveying method for their TRO operation. The success of this service led PhotoSat, in collaboration with Suncor, to develop a process for automatically mapping the thickness of the mature fine tailings dewatering cells in increments of 15cm. This helps them reduce existing mature fine tailings inventory. The isopachs are provided in map (polygons) and tabular forms.

Satellite photo of MFT system 1

Satellite photo of MFT system 1, July 27, 2014                     Elevation image of MFT system 1, July 27, 2014

 

 

Isopachs (thickness) of MFT System 1

Isopachs (thickness) of MFT System 1, June 29 to July 13                  Thickness changes, July 13 to July 27

 

The spreadsheet data we provide also includes MFT volumes since the last pour, the total area in m2 covered by MFTs, the area of the polygons, the utilization of the polygons, and the MFT lift thickness.

Mature fine tailings mapping from our 15cm accuracy topographic surveys improves the monitoring and measurement of the tailings, providing Suncor with a cost-effective and reliable alternative to GPS surveying and aerial LiDAR mapping. Using satellites also reduces safety risks for field crews.

Next time we’ll look at how Suncor has adopted toes and crests mapping as part of their TRO process.

For more info on our topographic surveys contact us at info@photosat.ca.

 

 

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.

Penasquito satellite photo

Seeing in Stereo: Satellite Mapping, Mining Volumetrics, and Gold

Peñasquito gold mine is Mexico’s largest gold producer. Two pits, Peñasco and Chile Colorado, produce gold, silver, lead and zinc, to the tune of 567,800 ounces of gold in 2014. The mine sees its future in a copper-gold ore located in tactites beneath the current workings.

Peñasquito’s owners boast proudly on their website that the mine ‘achieved commercial production in 2010, on schedule and on budget.’ That’s no small feat in an industry dogged by unexpected setbacks, and in turn it’s no small measure thanks to fast, accurate and effective mapping and volumetric measurements.

Back in early 2010, Photosat stepped in to calculate mining volumetrics at the Peñasquito mine site.

The goal was to estimate the volume of rock and overburden mined at the site. We used our own high accuracy geophysical processing technology to make volume estimations directly from stereo satellite images that could show detailed 3-dimensional changes.

We started by taking two sets of stereo satellite images, a month apart: one in January and the next at the end of February.

Then we ran these stereo Worldview-2 satellite photos through our own proprietary geophysical elevation processing system.

The beauty of this approach was that we could work directly from the automatically derived elevations to estimate mining volumetric changes in the leach pad, the waste dumps, the ore stockpiles and even the pit itself. All calculations can be done with instantaneous sets of satellite photos – a snapshot of the entire mine site.

Penasquito mine volume decreases

Using the changes in the month-long gap we could determine the volume decrease from January to February, giving highly accurate calculations of the amount of rock and overburden removed from the mine pit.

We based our volume calculations on a 125% expansion factor for blasted rock, and came up with an estimate for the total removed from the pit in a month of 6,928,100 m3 of blasted rock, or 5,542,400 m3 of unblasted rock. This is necessarily a slightly inaccurate figure, but as mining operations go on fine-tuning becomes possible; knowing the proportion of the total removed made up of overburden with a lower expansion factor would tighten up the figures, for instance.

 

Penasquito mine volume increases

Meanwhile, waste dumps, ore stockpiles and leach pads grew by an estimated 6,091,000 m3 during the same period.

 

Leach pad satellite images

This final image shows a detailed view of the volumetric calculations over the leach pad, with an addition of 505,400 m3 over the month.

Find out more about PhotoSat’s mining volume calculations.

Accelerate Mining Volume Measurements with Satellite Topography

Accurate mine planning requires continually adjusting the plans for the situation on – and underneath – the ground. Resource quantities and locations are changing frequently, and mine layout is affected by blasting, tunneling and ore removal. That’s especially true in open pit mines, but all mining engineers face the difficulty of working with the same digital elevation data while the ground shifts.

In fact, that’s one problem that more efficient communication between the mine face and site and the engineer simply can’t solve, because no one on the ground has a high-level overview either. What’s needed is an update of the original elevation data to reflect what’s happened since.

A common method of doing this is with LiDAR (Light Detection and Ranging). But LiDAR is expensive and time consuming, so we need a mapping system that can be used more often. The only snag is that it has to both deliver similar accuracy and cost significantly less to permit more frequent use.

Step forward satellite topography.

Satellite topography using new, geophysical processing techniques results in similar accuracies to LiDAR and can be used for yearly, quarterly or monthly reconciliations, allowing engineers to work with accurate representations of what’s really happening on the ground. PhotoSat’s satellite elevation mapping for mining volumes has proven accuracies of better than 30cm, providing a clearer picture.

Mining volume changes over an open pit

Volume changes over an open pit mine

 

That means that when it’s time to make volumetric change measurements in pits, stockpiles, waste dumps and tailings, satellite mapping lets you view and analyze the situation simply and easily. Our clients tell us that one of the main advantages of using our satellite system is the ease with which they can check on as-built locations of buildings and structures and reconcile them to the original plan. Reconciliation can even be on a biweekly basis if the project is moving fast. That helps engineers with tailings management, and also makes life easier and safer for on-the-ground surveyors, resulting in greater accuracy and fewer injuries.

How can a satellite system deliver biweekly updates? Partly because after ground-based scans have been acquired, the images have to be compiled. In the case of a system like vehicle-mounted ILRIS (Intelligent Laser Ranging and Imaging) that’s the bottleneck; from raw data to point cloud to the computer processing and satellite location necessary to produce a useable image, nothing much can compete with the 8 days PhotoSat’s technology can take to produce a useable result.

Satellite image with mining volumes

Satellite photo with mining volume changes

 

Finally, using satellites rather than ground-based methods removes the need for surveying to take place on or near the mine site. As a result, the surveying process is safe and never needs to interfere with mine operations. There’s no risk of damage to vehicles or injury to surveying personnel when your imaging is done from space!

To find out more about how satellite topographic mapping can help make mining a safer and more efficient process, leave us a comment or contact us at info@photosat.ca.

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