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And what has this do with Drones?

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At this time of year (Autumn), the woods and trees are so beautiful with the array of greens, yellows, reds and browns. Have you ever wondered why they are that colour? We just take it for granted. Why are leaves green? And why is a guy who is setting up a drone business going on about the colour of leaves?

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Leaves are green because our minds decipher information received from our eyes, it goes like this in the simplest form:-

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Visible light is 400 to 700 nano-meters in wavelength and light is a range of wavelengths as shown in the diagram below. Our eyes and brains can only decipher visible light.

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Light of all wavelengths is emitted from the sun millions of miles away, this light is scattered, by atmosphere scattering, *“the unpredictable diffusion of radiation by particles in the atmosphere”. There is a tendency for short wavelengths to be scatted more rather than longer wavelengths, hence a blue sky. As sunlight interacts with the earth’s atmosphere it scatters the shorter (blue) wavelengths more dominantly. At sunrise and sunset the sun’s rays are scattered on a longer atmospheric path, hence more scatter and absorption of the shorter rays leads to longer wavelengths of orange and red being dominant to our eyes. Many of the dangerous wavelengths / radiation is reflect by or absorbed by the ozone layer.

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The sun light finally hits earth and is reflected, absorbed and transmitted by different materials, such a building. organic matter, water, dust. This matter absorbs, reflects and transmits this light (wavelengths) differently depending on its physical qualities.

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Now back to leaves!

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Photosynthesis is the process of plants absorbing energy from light to grow, and chlorophyll is vital in this process. Chlorophyll absorbs light especially the blue wavelengths and to a lesser extend the red wavelengths. It absorbs very little green wavelength which is reflect back. This reflected green wavelength is picked up by our eyes and transmitted to our brains producing the green colour of leaves. HEY PRESTO WE ARE THERE!!! 

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So what has this got to do with drones?

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Drones or UAV (unmanned aerial vehicles) are the buzz technology which is set to transform our lives. It will touch every one of us in many ways. While there are many reported uses of drone technology, much has not yet transitioned to a working model, such as drone taxi’s or pizza delivery drones, although in some remote areas, drones are used for such things as small medical  prescription deliveries. These ideas will become reality in time, but regulation, risk management and safety has to catch up with reality before they become real and mainstream.

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For now a civil drone is used mainly for data capture, the drone allows the facilitation of this; by this it is a means to carry the sensor closer to the earth than satellite plane or helicopter. Which is more cost effectively, safer and timely. 

 

This data is captured by camera, a variety of multi-spectral sensors, and infrared cameras. These sensors catch a much longer range of light wavelengths that our eyes such as ultraviolet and infrared.  This is done in much the same way as our eye captures visible light and our brains decipher that information. Sensors capture the different light wavelengths, store it then sends this data to a computer that deciphers the information like our brain and produces images.

 

We have been taking images of the earth, countries, crops and forests for many a year. This capture has been done by satellite, planes and helicopters. All very expensive to operate and very few of us can fly one. The drone is a game changer. “Drones can capture images 16 X higher resolution than the traditional methods……reshaping aerial data capture with affordable and high pixal resolutions. (https://sentera.com/aerial-imaging-infographic/)

 

Aerial data acquisition using a UAV makes this data capture affordable, more comprehensive, convenient and accessible. With cutting edge sensors and powerful image processing software, drones not only facilitate better data acquisition, but also better analysis and decision making for the end user. They also drive considerably lower procurement cost to the traditional method of data retrieval of helicopter, scaffolding hire or satellite.  A UAV and pilot eliminates costly labour and resources, decreases health and safety risk and lessens hazardous situations of putting people up high on scaffolding and elevated platforms, not only is a UAV and pilot very much safer, but also quicker.

 

Commercial Application of the UAV:-

 

• Agriculture management

• Fisheries & forestry management

• Pipeline monitoring, oil & gas,

• Mining and aggregate stockpiling

• Power-line monitoring including wind power turbine inspection

• Aerial photography including movie and TV productions,

• Infrastructure surveillance and inspection

• Real estate survey and photography

• Mapping and 3D imagery

• Search and rescue

• Wildlife monitoring

• Security

• Insurance

 

A considerable amount of film and photography is now facilitated by drones. We have seen stunning images of beautiful places taken from positions and angles that would be unheard of before drones were used.  This easily accessible photography can be used in many ways to capture pictorial information using visible light. What about the light we cannot see picked up by other sensors? This is one of the areas where a drone revolution is taking place.

 

Agriculture - The measurement of plant health, identify crop stress and quick elimination of pests or fungi.

 

Healthy and unhealthy plants reflect and absorb light differently. Healthy plants reflect more green light than red light hence a green healthy plant. Plants also reflect near-infrared light not picked up by the human eye, but detected by near-infrared sensors.

 

A healthy plant (green leaves) reflects about 50% near infrared and reflects about 8% visible light, while an unhealthy plant (brown, yellow leaves) reflects 40% near infrared light and about 30% visible light.

 

NDVI (Normalized Difference Vegetation Index) has been used in agriculture for many years and is the standard used to identify and measures plant health. It measures the photosynthetic activity and by taking the ratio of red and near infrared bands from a remotely sensed image the index can be calculated. NDVI compares the proportions of light captured across different light wavelengths (red, green, blue, IR) and calculates a value for each pixel of data captured on the sensor. A map is created for the area.

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An alternative and cheaper method than NDVI data that requires less expensive sensors is VARI “Visible Atmospherically Resistant Index” and can captured by an average camera. VARI is a measure of how green an images is and can detect slight difference between healthy and unhealthy crops.

 

With the exploitation of this data using drone technology a farmer is able preform regular flights, something that would have been too expensive prior to advances in drone technology. This data analysis is then used to calculate the vegetation index to assess plant health across the growing season. Crop scouting by drone can spot pest infestation on particular areas of the field allowing micro management of pesticides. The micro management of less healthy growth in field areas also allows for micro management of fertilizers to be implemented to help recover healthy growth. This will reduce costs for pesticide and optimize fertilizer usage, reducing chemicals released into the environment, reducing costs and increasing crop yield. A very positive outcome for all.