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.