Greetings, Season Spotters! This is Don Aubrecht, a postdoctoral researcher at Harvard. Now that you’ve learned how we get cameras above the canopy, you might be curious what sort of hardware we are using.
After careful study and experimentation, we learned that a super fancy camera is not necessary to get good images for studying phenology. True, expensive DSLR cameras will produce large, high-resolution images that look amazing, but the file sizes are too big. We need to be able to store all the images from the large and growing PhenoCam network. Also, we don’t need millions of pixels for our analyses — a few hundred or a thousand are plenty.
Our current go-to camera is the StarDot NetCam SC. It starts life as a web-enabled digital security camera, and we change a few settings to turn it into a scientific instrument. You can see one just to the left of my head in the image below. They are small and remarkably robust. We’ve had many get struck by lightning and only need their network card replaced — an inexpensive fix and it’s back up and running!
To make the camera into a scientific instrument, we change settings that are normally used to make the digital images look pleasing to the human eye. This includes things like white balance and sensor gain, and we change the defaults to fixed values so that when we see changes in greenness in a time series, we know that it is due to the vegetation, not the camera settings. The cameras still take pretty pictures, but now we can analyze them quantitatively.
Besides their capability to allow us to change image settings, the StarDots have become our standard camera because they act as mini web servers. Each camera runs a very simple Linux operating system and can send us images over the internet on a set schedule.
Some of our StarDot cameras also have a removable infrared filter which lets us take two types of images: a visible light image (which is what you are used to seeing), and a visible+infrared image (which gives additional information about the vegetation). An example is shown below. The visible image is on top, and the visible+infrared image is on the bottom.
You can see in the visible+infrared image that the green and brown grass looks uniformly gray, while the little ornamental plant in the foreground is quite white. Also, the dark band of rock on the far hillside is much more apparent in the visible+infrared image. We use this information to help select vegetation from rock and soil.