Linking trail cameras and remote sensing

One of our research goals is to understand where wildlife can be found across the state and how that distribution changes seasonally. Seasonal changes (i.e. phenology) are associated with the availability of cover and food for wildlife and are important in understanding the variability in species distributions. In this project, we are utilizing two ways to understand phenology: remote sensing data and trail camera images.

Remote sensing data:  Snapshot Wisconsin is partnering with the National Aeronautics and Space Administration (NASA) to use earth-observing satellites to capture broad scale changes in forest phenology across the state. NASA employs several satellites such as MODIS and Landsat that orbit the earth and take ‘pictures’ of the surface at regular intervals. These ‘pictures’ are composed of measures of light reflected off the surface of the earth. Different land cover types reflect light in distinct ways, and change across seasons as plants begin leaf growth, reach peak green-up, and begin to shed leaves in autumn. Using images from space, we can capture changes in forest productivity, and the timing of forest green-up and brown-down across large regions.

Trail camera images: In addition to the satellite data, we’ve leveraged the trail cameras to capture site specific phenological data.  You already know that the trail cameras take motion and heat triggered images. In addition, each camera is programmed to take one photo at approximately 11:00 a.m. each day, generating a set of time series photos.   The below video shows an example of green-up at one of our camera sites.

11:00 a.m. trail camera photos taken over the course of 3 months

Another exciting application of these trail camera images is the opportunity to validate phenological models.  For a number of our cameras, we have fit phenological curves to the camera data (see below graph). Our analysis shows that the daily photo sets closely match MODIS satellite data. Future work will link this type of phenological data to our understanding of wildlife populations.

Comparison of trail camera phenology (red) to MODIS phenology (green) for a trail camera