How Do Drones Work?

PlacerGold Drones, Science October 9, 2015aerial imagrey, autopilot, drone, infrared, lidar, mining drone, orthomosaic, payload, radio, uav, vancouver, Vancouver drone 1 Comment

Five years ago you rarely heard the word “drone”. When you did it brought up images of military air strikes and futuristic sci-fi movies. In 2015 drones have become commonplace and are starting to be used in many industries. A drone provides many advantages over traditional fixed wing data collection and the low cost makes it a practical solution to many problems. Hobbyists are also quickly getting into the game due to dropping prices. It is amazing how many people will drop $1000 or more on these high tech gadgets.

Drones, also called Unmanned Aerial Vehicles (UAVs), are flying robots that are able to execute a task autonomously. They come in several different forms but they all have the same core components. The four critical drone components are Autopilot, Propulsion, Sensors, Payload.

The Autopilot

The autopilot is the essence of what makes a drone. In order for an aircraft to be called a drone it must have the capability to fly without human intervention. The usage of the word drone has been misconstrued in recent years. Just because an R/C aircraft has four rotors and a camera does not make it a drone, it muse have autonomous flight capabilities. Autopilots are sort of the brain of a drone. They monitor all the information coming in from the sensors and send signals to the control mechanisms based on their programming.

The autopilot software functions much like a thermostat. For example if the drone’s alitutde is set at a certain number the autopilot will contol the aircraft to maintain that number. If the drone rises higher the autopilot will adjust the controls so that the drone descends, if its too low it will set the controls to climb. The autopilot operates in this way for hundreds of different parameters such as airspeed, altitude, GPS position, attitude (3D orientation), and many more.

The use of autopilots goes back to at least the late 1940s when experimental aircraft were able to operate completely by computer control. Modern commercial airliners actually employ autopilots that can control the aircraft from takeoff to landing, the only thing they can’t do is taxi. Every time you fly on a commercial jet you are riding a large autonomous robot.

For a flight to be successful the autopilot must have the parameters for the flight such as flight path, altitude, flight restrictions and settings stored in its memory before takeoff. Once in flight the autopilot will use the preprogrammed information to follow a flight pattern and land at a predetermined location. Watching an autonomous drone in action is quite an experience, they can give the impression that they are thinking for themselves.

The Sensors

Sensors on a drone connect it to the real world. They perform the functions that the eyes, ears, nose and other senses do in a human. A drone can only know what the sensors tell the autopilot, much a like a human’s concept of the world is based on what we can see, smell, hear and touch. For example a drone will not have any idea it is heading directly for a tree unless it is equipped with an obstacle avoidance system. The same is true of hitting the ground or a person who walked in front of the aircraft. The pitot/static system is used to measure the current airspeed and altitude. This sensor measures air pressure from a forward facing tube, as air speed increases so does the pressure. The static tube measures the change in barometric pressure which decreases with altitude. The pitot system also measures the wind speed by comparing the airspeed to the GPS speed.

Most drones have a GPS system which is the basis for autonomous flight plans, and in the case of very accurate GPS systems altitude can be measured. Drones also have a 3 axis accelerometer which monitors the aircraft’s orientation relative to the horizon. Accelerometers are also used in smart phones, they are the device that senses when you shake or tilt the phone. More complex drones have fancy inertial measurement units (IMUs) which use gyroscopes and other methods. Drones have servos which monitor and adjust the position of control surfaces such as ailerons, or rudders. Servos are electric motors that are calibrated to precisely place their control arm. There are countless optional sensors which can add new capabilities to a drone. Some optional sensors are altitude lasers or radar, trasnponders, voltage sensors, magnetic compass, and obstacle avoidance sensors.

The Propulsion System

There are a variety of propulsion techniques in use in drones today. The majority of drones use electric motors. The typical drone that most people would think of is a multirotor helicopter. These use electric motors with a propeller on each. Thrust of each motor is carefully controlled to maintain the correct speed, altitude and attitude of the drone. Small fixed wing drones often use electric motors too although usually just one. They are typically propeller driven as well and they work together with the control surfaces to make a flight successful. Electric motors rely on battery power and can fly as long as the batteries hold a charge

Gas or heavy fuel motors are used on larger fixed wing drones and are still usually propeller driven. There are a few drones out there using jet and turboprop engines such as the Reaper (armed version of Predator). Rocket engines have been used for decades in target drones. Targets were one of the first uses of drones by the military. Its hard to believe but military forces around the world routinely shoot target drones which cost $20,000 and up each. Gas or rocket drones run on a fuel source and their flight duration depends on how long the fuel lasts. Gas drones also have batteries for their electric components and some of them have an on board generator.

I was part of the team that developed this drone

The Payload

Payload is often the area where the most development work is focused. After all these robots are flying for a purpose. The most common payload is some form of a camera. The majority of drones out there are either taking photos or video. Most small drones consist of a multirotor with a GoPro camera on a gimbal. Mapping drones like the one used by WestCoastPlacer have a down facing high resolution camera that is triggered by the autopilot. Mapping drones also record the GPS position and aircraft orientation with each photo for use in processing. Different kinds of cameras can be used such as infrared, multispectral and hyperspectral.

LiDAR laser scanners are starting to be mounted on drones too. It has taken a long time to miniaturize LiDAR sensors to the point that a small-medium sized drone can carry one. Drone LiDAR sensors to date have not been able to provide classification so that a bare earth model can be produced.

Magnetometers are being mounted on drones too (Pioneer Exploration, GEM). These are geophysical sensors used to measure changes in Earth’s magnetic field. This sort of data is used in mineral exploration and location of land mines and submarines. There are many more payloads out there such as air quality sensors or wifi internet repeaters.

The Communication System

Another important component of a drone is the communication system. It is technically possible to operate a drone without real time communication since they fly autonomously however it is irresponsible and in most places illegal to do so. An unmanned aerial system will include some form or radio communication with the operator. The operator will have a radio link hooked up to a field computer with base station software to program the drone and monitor in during flight. On board the drone will be some form of two way radio system which will transmit data to the base station as well as allow the operator to issue commands. Telemetry data received from the drone allows the operator to monitor the flight and make sure that everything is working properly. Examples of telemetry data are things like airspeed, battery health or fuel level, position and orientation.

Typical radio frequencies that are used are 900 Mhz, 2.4 GHz or 5 Ghz. Range of a standard system is 5-10 km. Factors that affect radio range are frequency, transmit power, antenna choice and terrain. Some drone operators have had great success using directional and helical antennas. Some helical antenna systems are capable of communicating up to 100km away. Cheaper drones communicate via WiFi (also a form of radio) to a smartphone or tablet. WiFi range is limited to several hundred meters but can be extended with directional antennas.

HelicalAntenna — Helical Directional Antenna with Tracker

Cellular modems are used in some drones utilizing LTE/GSM networks and can greatly increase the operating range. Essentially you can fly anywhere there is cell coverage. Satellite systems are also used which operate on a satellite phone network such as Iridium. Theses communication systems have virtually no limit on range but have slow throughput and expensive by the minute billing.

All the individual parts of drones work together to execute a flight and achieve the goal of the operator. New uses are being discovered for this technology every day. The low price and superior data quality make the UAV a powerful tool for collecting aerial data. In the coming years we are going to see drones used in more and more industries. It just makes sense.

Check out our drones page to see the drone services provided by WestCoastPlacer.

Where Does Placer Gold Come From? – Part 3 Placer

PlacerGold Science May 30, 2015alluvial, eluvial, gold, gold mining equipment, gold pan, gold panning, paleo-placer, placer, quartz vein, vancouver, Witwatersrand 4 Comments

Placer gold mining has been practiced for thousands of years with evidence dating back as far as 2600 BC in ancient Sumeria and Egypt. The technology required is minimal with only a gold pan you can refine gold in a placer deposit. The word “placer” comes from the spanish word meaning “pleasure”. Perhaps an allusion to the delight of finding precious metal in a river bank. The word was spread as gold bearing gravels were discovered in parts of North America colonized by Spain. In fact the discovery of gold the primary motivation for Spanish explorers to dig deeper and deeper into the newly discovered continent.

As we discussed in the part 1 and part2 gold is created in fantastic cosmic explosions. It has traveled across the universe and made up a small part of the material that the earth formed from. Tectonic and volcanic forces collected gold in concentrated lode deposits where it can be mined. The concept of how gold transfers from lode deposits to placer deposits is pretty straightforward. Rock holding the gold bearing veins or ore is slowly chiseled and broken by weathering and erosion. The erosive forces of water, wind, and ice transport rock fragments into drainage systems such as streams and rivers. Gold and other heavy minerals will settle out in areas in the stream where the water loses momentum or creates a trap. These traps form into placer deposits over time.

Placer deposition is driven by gravity. Gold is very dense, meaning that compared to another substance of the same volume it experiences a stronger pull of gravity. There are other principles of physics that apply to placer deposition. The property of inertia is the resistance of any physical object to any change in its state of motion. Less dense objects require less force to move them and in the case of a stream will travel farther and faster than heavy objects. Gold has a density that is twenty times that of water and about 8 times the density of sand. Another factor in the formation of placer deposits is Archimedes’ principle which states that the force of buoyancy on an object is equal to the weight of the displaced fluid. This principle was historically used to measure density of gold by Archimedes himself. As gold is many times more dense than water the force of buoyancy on submerged gold particles is much less than the force of gravity. So gold in a stream is held in place by gravity and resists movement due to its weak buoyancy and strong inertia.

There are several types of placer deposits. There are alluvial placers, eluvial placers, beach placers, eloian placers and paleo-placers. For each type of deposit there are miners who specialize in that type of deposit. All placer deposits have concentrated gold from its source in some kind of trap. The vast majority of the placer gold that is mined in the world is of the alluvial variety.

Alluvial placer deposits are formed in watercourses such as creeks, rivers, streams and deltas. The gold is eroded from lode deposits and carried into the watercourse through rains and melt. Once into a stream it can be moved great distances. Gold does not move easily in a stream due to the inertia and buoyancy forces described above. It takes many years for gold to make its way into a stream and to travel within it. The gold will move along the bottom of the stream until it reaches a point where the water loses velocity or it is physically trapped. Typically gold will accumulate on the inside bends of a river where the water velocity is lower. Large rocks or outcrops can create a natural riffle or eddy where the water slows down and dense material will accumulate. Waterfalls are another great trap for gold.

Alluvial placers can be broken into several groups. Flood gold is placer gold that moves during annual floods or other flood events. Gravel bars and upper sections of stream sediment are where flood gold is usually found. This type of deposit generally consists of small flake and flour gold since they move more rapidly than nuggets. Flood gold is actively being deposited and will replenish year after year

Streambed placer deposits are essentially the same as flood deposits except that they no longer move. Streambed placers are found in a current watercourse. These deposits typically consist of gravel that is settled in the stream bed. To produce a streambed placer you have to mine under the water. Techniques that can be used are sniping, suction dredge, or diverting the water using a dam such as a wing dam.

The third type of alluvial placer deposit is a bench placer. Bench deposits are part of the old stream bed before it cut into a deeper channel. Benches can contain huge amounts of gold if the river carried gold at that time. A bench is typically flat on top and may appear like steps coming down the valley side. Benches can be mined using conventional mining equipment since they are usually high and dry above the current river.

Eluvial placer also known as residual placer deposits are formed before any water transportation has taken place. These deposits form close the source of hard rock gold. Eluvial placers will contain much large particles of gold than other types because it takes a lot of energy to move large nuggets. Often quartz will be found with gold still attached in Eluvial placers. These types of placers are formed by weathering and decay of the host rock that holds gold. Areas where there is a lot of iron can break down rapidly as the iron oxidizes. The lighter overburden is generally washed away and unsorted gravel and heavy material is left in place. These deposits are generally small and very attractive to small miners they also are close to gold bearing veins which can be very exciting.

Beach placers are deposits that occur on the edges of large lakes or the ocean. The wave action on the beach is the mechanism that concentrates gold and other dense minerals. Gold can either be carried to the beach by an alluvial system or eroded directly by waves. A famous beach placer is the deposit in Nome, Alaska which is featured in the TV reality show “Bering Sea Gold”.

Eolian placers form in areas where wind is the main mechanism of erosion and not water. Eolian placers are similar to Eluvial placers in some ways, they occur close to the hard rock source, and are poorly sorted. Wind does a terrible job of moving gold. In Eolian placers the overburden is swept away by strong winds and leave the heavy ore behind. They occur primarily in desert regions such as the arid regions of Australia.

The last type is paleo-placer deposits. These are any of the above placer types that happened a long time ago. By a long time we are talking about millions of years. Paleo-placers were once placer deposits but over time they have been hidden and covered in sediment. There is often no sign at the surface of ancient river systems below. Paleo-placers can be ancient river channels, benches or sedimentary rock formed from old placers such as quartz pebble conglomerate. This kind of deposit can amount to huge quantities of gold and make you very rich. The largest known gold deposit in the world in Witwatersrand, South Africa is one of these. Over 1.5 billion ounces of gold has been mined in Witwatersrand. Deposition occurred approximately 3 billion years ago in Witwatersrand, and it is estimated that 50% of all the gold mined on earth came from that deposit.

That’s the story of where placer gold came from. It was created in incredibly powerful explosions from dying stars. It made up the earth as it formed and was squeezed into concentrated deposits by volcanic processes. The veins eroded into river systems and hopefully made its way into your gold pan. Gold’s unique properties of density and its resistance to corrosion and most other chemical reactions allow it to build into the kind of deposits that we can find and mine.

Where Does Placer Gold Come From? – Part 2 Deposits

PlacerGold Science May 14, 2015carlin trend, epithermal, gold, gold mining, greenstone, lode gold, mother lode, placer, porphyry, quartz vein 3 Comments

In part 1 of “Where Does Placer Gold Come From?” we discussed the origins of gold and how it appeared on earth. Now we’ll discuss how it moves into mineable deposits.

Gold is spread relatively evenly throughout the crust of the earth at approximate concentrations of 1 part per billion. To put that into contrast, low grade mineable gold deposits need to be concentrated to at least 1 part per million which is about 1000 times more concentrated than the background. High grade gold deposits are in the order of 20-100 ppm. Gold concentrations are usually expressed in grams per ton, which is interchangeable to ppm.

So if gold is evenly spread through the crust how does it become concentrated? There are several natural processes that allow this to happen and they are all driven by the same force, plate tectonics. Plate tectonics is the force that moves continents, creates mountains and most volcanoes, and of course earthquakes. The image below shows the current tectonic plates and their names.

The plates are constantly moving, crashing into each other and subducting, they are pushed by convection currents in the mantle. In the distant past there have been several supercontinents where all the continents had come together to from one. Past supercontinents have names like Rodinia, Godwana and Pangea, it is predicted that a new supercontinent will occur in the next 250 million years.

At the boundaries of these plates is where the excitement happens. It is at these areas such as the West coast of North America where volcanic processes squeeze gold into veins. There are two main ways that this happens. Orogenesis (mountain building) takes place as the force of two plates hitting each other forms mountains as the edges of the plate buckle and slide. In the mountain forming process rock is squeezed to the point of breaking and creates fissures and faults that extend deep into the crust. These cracks allow heated and pressurized water to come up the cracks.

The other way is driven by volcanoes forming from the subducted plate. When the edge of the plate is far enough below the surface it re-melts and the newly molten rock builds up pressure. This pressurized molten rock is what forms the volcanic chains inland from the subduction zone. As volcanoes form they crack and fissure the surrounding rock and contribute to the same epithermal process.

Imagine the rock as a sponge and when it is squeezed the water is expelled through the cracks. It is actually the same way that hotsprings work but with more squeezing. This kind of gold mineralization often takes place near volcanic or geothermal activity such as hot springs or geysers. When the mineralized water cools it leaves behind the minerals in solid form which we then call a vein. Typically we are looking for quartz veins. Vein deposits are often called lode deposits in artisanal miner vocabulary. Placer miners will often refer to the “mother lode” that is the quartz vein or veins that broke down into rich placers.

There are other hard rock gold deposits other than epithermal lodes. There are Greenstone, volcanic massive sulphides, porphyry and Calrin trend deposits. All of these depend on volcanism as well and occur in similar ways as described above. Areas high in volcanoes and seismic activity are good places to look for gold. The Pacific ring of fire is an area surrounding the boundary of the Pacific tectonic plate. This area contains 3/4 of the worlds volcanoes and is responsible for 90% of the world’s seismic activity. In the gold rushes of the 1800’s prospectors envisioned a world wide gold belt. It wasn’t until the 1950’s that plate tectonics became an accepted scientific theory and decades later we mapped out that gold belt.Of course not all gold is found in the ring of fire. The largest known gold deposit on earth is in Witwatersrand, South Africa. It is estimated that 50% of the gold mined on earth has come from this mine. Witwatersrand is actually a huge placer deposit from 3 billion years ago. In my next post we’ll finally get to the formation of placer gold deposits. Stay tuned.

Check out Part 3 on how gold placers form:

Where Does Placer Gold Come From? – Part 3 Placer

Where does placer gold come from?

PlacerGold Science May 9, 2015gold, gold mining equipment, gold pan, lode gold, placer, solar system, supernova 0 Comment

If you are trying to find gold it helps to know where it came from.

To start with there is only one kind of gold. Placer gold and lode gold both come from the same place and are made of the same stuff. Gold is not actually formed on earth it was formed millions of years ago in distant stars. In large stars, much larger than our sun elements are combined together in their cores through the process of nuclear fusion. Our sun like all stars runs on fusion too but it does not have enough mass to produce atoms larger than carbon or oxygen. Larger stars can generate the gravitational force and heat in their cores necessary to produce elements as heavy as iron. To create things like gold even more energy is required and that takes place in a supernova.

When a large star runs out of light matter the fusion reaction is no longer sustainable and the star begins to collapse on itself very rapidly. The supernova collapse takes place in a matter of seconds. While the star is collapsing it produces heat very rapidly and explodes in what is essentially a humongous nuclear bomb. Supernova events are so bright and powerful that they are brighter than then entire galaxy that hosts the star. This nuclear explosion allows for higher energy fusion reactions that can produce heavy elements like gold. The explosion also scatters the newly created material over great distances.

So how did the star dust make it into the mountains and rivers on earth? When our solar system began approximately 4.6 billion years ago it was a cloud of dust and gas called a nebula. This nebula was composed of the remains from older stars that had spread their guts around the universe in supernova explosions. The molecules of the nebula naturally pulled on each other by the force of gravity growing more and more dense. As the nebula was collapsing in on itself it also started to spin faster and faster. The condensing and spinning action formed the nebula into a disk, much like you spin dough into a pizza. In the center where the force of gravity is the strongest a new star was created, our sun. The swirling mass around the sun clumped together into the planets, moons, asteroid and comets that we see today.

The early solar system was different that it is today. The big planets did not form all at once, it was a gradual process. Small plantoids formed first and crashed and coalesced into each other to form larger planets. In theory the distribution of gold was basically even in all the rocky material that made up the early solar system. In the early earth, while it was still completely molten the heavy material (such as iron and precious metals like gold) all sunk to the center of the planet to form the core. The process is similar to the way that dense material sinks to the bottom of your gold pan. If you could mine the core you would be very rich but it would be very difficult with current gold mining equipment. Current scientific theories estimate that there is enough gold in the core to cover the surface of the earth with a 4 meter thick layer of pure gold.

We can only reach gold that is trapped in the crust of the earth. The precious metals in the crust were put there by meteor bombardments that took place after the crust had formed. As these meteorites crashed into the surface of the earth they disintegrated and mixed their material into the upper mantle. The meteorite guts had the effect of enriching the amount of precious metals in the crust.

So we know where gold came from and how it was formed. Stay tuned for a future post to learn how the gold formed into deposits in the mountains and streams that we mine.

Check out Part 2 & 3 here:

	How to Get Started in Gold Mining
	Search for Slumach’s Lost Gold Mine
	Types of Placer Wash Plants
	Top Ten Gold Rushes of BC
	How to Lose Your Shirt in Placer Mining