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Drones detecting NDVI in crops

  • By: Phil Lyons
  • Jul 03, 2017

One of the key benefits of what data a drone can provide to growers, is in the Near Infrared (NIR) spectrum. To gain a greater understanding of these type of images, a short explanation of what NDVI or Normalised Difference Vegetative Index is needed.

All plant life absorbs radiation from the sun and reflects various wavelengths. Most plants will reflect green light – which is why humans see them as green. These plants are also reflecting a lot of Near Infrared light which is invisible to the human eye. The more NIR a plant reflects is an indication as to its health, or lack of ‘stress'.

Now plants can be stressed from a number of different reasons – lack of nutrition, not enough or too much water, weeds, or a bug infestation. Interestingly, an NDVI map does not tell us WHAT a problem is, but WHERE the problem areas are located. Then it's the job of an agronomist to ground proof these areas and prescribe corrective treatments.

As importantly, in those areas that are very ‘healthy' and are not showing stress, they may not need any further chemical application – saving large amounts of money in crop treatment / fertiliser costs.

Whilst NDVI imaging has been available for many years from satellites, there are some limitations. Timing has to coincide with the satellite being overhead and the day not being cloudy or overcast. Generally the image resolution is also a consideration, as pixel sizes can range up to 5 or 8 mtrs.

The data coming back from a drone's image is usually under 30 cm. For some crops, this is very important as the grower needs to identify individual rows or trees. Similarly, growers may need to scan their crop in the morning and commence precision spraying that afternoon.

 A key to maximising these benefits, is in what camera to use for specific crop data. Whilst modified, digital cameras can capture NIR and are relatively in expensive, there are a range of new multi spectral cameras that allocate different wave lengths to individual lenses, producing a lot more data in higher accuracy.

There is a lot of new technologies emerging with high tech cameras and the benefits are that most drones can still carry these new cameras as they emerge. Even the basic NDVI image will allow most growers to save many thousands of dollars in their chemical costs and help improve their yield.

For more information contact: Phil Lyons at Falcon UAV. www.falconuav.com.au