Professional foresters use simple hand-held densiometers or expensive (and heavy) fish-eye cameras to measure forest canopy closure – that is, the percentage of an area looking upward that is covered by leaves and branches. This poster describes a mobile application created for the Digital Earth Watch (DEW) and Picture Post Network that uses the color information in a digital photograph to estimate canopy closure. The mobile app creates a “mask” based on user-defined regions of interest in the photograph and calculates the percentage of pixels in the photograph that meet the criteria. The user can create and verify the mask right in the field, rather than having to do calculations back at the lab. Preliminary research indicates that the app is more sensitive than the densiometer. Tests will be carried out to compare readings with those using a proprietary fish-eye camera setup. For the tests, we will use the digital camera that comes with the mobile device and also an inexpensive fish-eye lens attachment, to determine the best method for using the CanopyApp for professional and educational studies of forest dynamics.