Near Infrared for crop surveysNear Infra Red (NIR) is closest to the visible region of the spectrum. NIR, or red edge as it's often referred to, is ideally suited to gathering data on vegetation. It's used widely to monitor the health of crops because it can detect the levels of chlorophyll. It compares near infrared levels with red light from the visible band and then calculates something called NDVI - Normalised Difference Vegetation Index. Vegetation that's actively growing and producing energy from photosynthesis, absorbs most of the red light that hits it but reflects much of the near infrared light. Vegetation that is diseased, stressed or dead reflects more red light and less near infrared light. Flying over a field with a drone equipped with a near infrared camera can produce dramatic evidence of the different state of crops. Images can show areas that need spraying for disease, require extra nutrients or need the amount of water adjusting. It can also indicate areas that might be of interest to archaeologists or possibly the police. What is a near infra-red camera? Most digital cameras have a filter which blocks infra-red light and stops it reaching the sensor. To make the sensor pick up near infra-red you have to remove that filter and replace it with one that blocks visible red, greed and blue light. [caption id="attachment_2161" align="aligncenter" width="555"] 3 images of the same field - normal, NIR and combined. Credit: Agribotix[/caption]
Getting a thermal camera into the airSo what about attaching a thermal camera to a drone? First of all you'll need to allow for having at least two cameras on board - one normal visible spectrum and one thermal. You'll need a standard sensor to provide a video feed for flying the UAV but you will almost certainly need another one to track down and line up your subject before switching to thermal. And it will help if that camera has the same field of view as the thermal one. Attaching a small first person view (FPV) camera to the same mount or gimbal as the thermal would make sense, provided the FOV was the same. As with a standard, electro-optical camera, the thermal sensor output can be recorded onboard and fed a signal to a monitor on the ground. Assuming that you'd need a pilot and a separate camera operator, then you'd need one or even two FPV cameras for the pilot too. There are simpler configurations that use one of each type of camera side by side. For example Skywatch have incorporated a Forward Looking Infrared (FLIR) into Anthea Technologies' Huginn X1. The operator can switch from one camera to the other. This type of quadcopter is often used by emergency services, humanitarian relief teams and conservation organisations. [caption id="attachment_2172" align="aligncenter" width="555"] The Huginn X1 with infrared and optical cameras side by side[/caption]
Here at Heliguy we're working on ways of using different sensors on our range of multirotors that would normally carry videos or stills cameras. We'll keep you posted an any developments as they happen.