The photocanopymeter

A photo process of measuring the density of the forest canopy cover over a fixed point in the forest is described. A pin-hole camera with film transport was constructed. The pin-hole was used to eliminate spherical distortion of the 'Fish-eye' lens ground for 90 deg wide angle photography. The 90 deg field of view was used to comply with Weather Bureau standards for precipitation gages, where it is required that the gage must be in the clear at 45 deg in all directions of obstructions. The camera is leveled and oriented N & S, pointed up and a time exposure of approximately 2 seconds is made over each snow sampling point on a snow survey course. A dot planimeter grid was developed for sandwiching with the negatives from the pin-hole camera shots. Dots covered by forest canopy are counted and proportioned to uncovered dots to obtain the percent forest canopy cover over each sampling point. Photographs of the camera, negative, grid and conversion tables are shown along with an illustration of the tabulation forms for data.