Done Mapping [Eyes in the Sky]

Part 1

As everyone knows Drones or UAV [Unmanned Aerial Vehicle] have become part of everyday life, love them or hate them they are here to stay for better or worse. Not so long-ago drones were limited to people with budgets of $10000+, then companies like DJI and Parrot entered the consumer market offering drones with professional features for under $2000. Why you could even go to your local market and grab a cheap Chinese drone for as little as $30, good luck with using one of them for professional photography. I am actually guilty of buying one of those cheap drones purely to learn the basics of drone flying, as I knew that a crash or 2 wouldn’t hurt the hip pocket. Needless to say, the market drone has gone where all $30 drones end up 😉

Drones have both a fun aspect and a serious side, buzzing around a park with your mate can be seen as fun and harmless, however you still have responsibilities and law’s you must abide by. Due to the proliferation of cheap drones dumped on the Australian market CASA [Civil Aviation Safety Authority] have introduced a number of rules that must be followed when in control of a UAV. Then there is the professional use of drones from Military, Emergency Rescue, Farming, to High Resolution Mapping.

The Technology that is built into drones is simply amazing.

The latest drones have dual Global Navigational Satellite Systems (GNSS) such as GPS and GLONASS.

Highly accurate drone navigation is very important when flying, especially in drone applications such as creating 3D maps, surveying landscape and Search & Rescue missions.

When the UAV is first switched on, it searches and detects GNSS satellites. High end GNSS systems use Satellite Constellation technology. Basically, a satellite constellation is a group of satellites working together giving coordinated coverage and are synchronized, so that they overlap well in coverage.

The latest high-tech drones are now also equipped with collision avoidance systems. These use obstacle detection sensors to scan the surroundings, while software algorithms and SLAM [Simultaneous localisation and Mapping] technology produce the images into 3D maps allowing the drone to sense and avoid.  These systems use one or more of the following sensors to sense and avoid obstacles:

• Vision Sensor [digital cameras]
• Ultrasonic
• Infrared
• Lidar

The DJI Mavic 2 Pro and Mavic 2 Zoom have obstacle sensing on all 6 sides. The Mavic 2 uses both Vision and Infrared sensors fused into a vision system known as omni-directional Obstacle Sensing.

The DJI Mavic 2 obstacle sensing system is considered high-end drone technology.  The Mavic 2 will sense objects, then fly around obstacles in front. It can do the same when flying backwards. Or hover if it is not possible to fly around the obstacle.

When it comes to flight stability in windy conditions Gyro stabilization technology give the UAV drone its smooth flight capabilities. The gyroscope works almost instantly to the forces moving against the drone, keeping it flying or hovering very smoothly.  The gyroscope provides essential navigational information to the central flight controller.

The inertial measurement unit (IMU) works by detecting the current rate of acceleration using one or more accelerometers. The IMU detects changes in rotational attributes like pitch, roll and yaw using one or more gyroscopes.  Some IMU’s include a magnetometer to assist with calibration against orientation drift. This technology leads to ultra-stable positioning which is extremely important in the area of survey quality Photogrammetry.

Now that I have given you a brief taste of what technology goes into a drone let’s talk about its use and benefits in the area of Gold Prospecting and Mining. I own a DJI Phantom 4 v2 and fly it both privately and commercially mapping both commercial Gold mines and my own tenements. As an example, flying a 200-hectare mining leases at a height of 120m produces approx. 1000 images [20 Megapixel resolution] at a ground resolution of 3centimeters/pixel. I know this may sound a little confusing however to put the image quality into perspective a Google Earth image is 15meters/pixel.

An example of Image quality below for both a Google Earth Image and a Drone image of the same location and the detail difference is very clear.

Figure 1 [Drone Image 120meters @ 3cm/pixel]

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Figure 2 [Google Earth @ 15m/pixel]

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Now you may ask yourself once I have 1000+ photos what do I do with them, well that thought actually leads onto a completely different technology and it is called Photogrammetry. Through computer processing all of the images are seamlessly stitched together into a survey quality mosaic, allowing you the ability to measures both Distance / Area / Cubic Volume and even angles. I will cover this in further detail in a future article, but take it from me there are some very smart cookies out there that came up with these solutions.

To help you understand what sort of imagery can be extracted from a simple digital camera photo I have included samples from a pit I flew in WA.

Below are a number of images showing the different type of detail that can be obtained from a basic 2D digital photo. 1000 Digital images that have been manipulated on a computer to create a seamless survey quality digital mosaic.

Figure 3[1000 Images stitched together in survey rectified quality]

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Zooming in on the mosaic image shows the image quality available from the 1000 image set.

Figure 4 [Close up showing Drilling Rig]

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A Digital Terrain Model [DTM] can be extracted allowing you to both visualise and measure height. This is very handy when mapping contours and gulley’s of a large area.

Figure 5 [Digital Terrain Model showing Elevation]

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3D terrain can be extracted from the Image mosaic allowing you to measure angles, volume and height, shown here is the pit wall and access ramp.

Figure 6 [3D Image of Pit Wall]

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When it comes to personal use, I actually use a DJI Phantom 4 Pro v2 to fly my mining tenements and use the images for research purposes. To walk the ground of 200 hectares and see every little detail is almost impossible not to mention very time consuming. Once I have studied the image, I am then able to pinpoint areas of interest based on ground type / structures / old workings and even contours when chasing alluvial gold. I also have the ability to overlay Gold Assay results giving me an even better detailed map of where the most probable area for gold nuggets may be. This type of information at my fingertips gets me very excited as it is equivalent to finding the needle in a hay bale and not the entire stack. Time and money are precious and a little research can go a long way to your success at finding that elusive gold. I can personally vouch as to my success owing to the likes of drone technology and making it affordable to the greater public.

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Below you can see that I have taken Geochemistry soil samples from the DMIRS repository and plotted them on the high resolution ground image [Fully georeferenced]. From here I can place this map on my phone/tablet and use the inbuilt GPS to walk right to the exact location of the high AU reading. This should turn on the light bulb in your head, as imagine the possibilities 🙂 when out there swinging your detector knowing you are in a great area for detectable gold. For those unaware the average AU value in the earths crust is 5PPB and anything above 10PPB is considered anomalous and has undergone some form of concentration.

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Figure 7[Drone Image with Assay results plotted]

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For all us Victorians out there the same can be done, below is a sample showing Geochemistry soil samples overlaid on one of my custom maps available in the store.

Figure 7[Custom Gold Map with Assay results plotted]

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I hope you found this information interesting and that it has opened your eyes up to what is possible with a drone and a computer and the benefits it can bring to the world of Gold Prospecting.

For further information you can visit my drone section tryhardprospecting.com.au

I hope you enjoyed the read.

And don’t forget to lookout for Part 2 in a follow-up article.

Stay Safe