Johnson, Mark G., and P. F. Meyer. 1997. Mechanical advancing handle that simplifies minirhizotron camera registration and image collection. Journal of Environmental Quality . 27(3):710-714
Minirhizotrons in conjunction with a minirhizotron video camera system are becoming widely used tools for investigating root production and survival in a variety of ecosystems. Image collection with a minirhizotron camera can be time consuming and tedious particularly when hundreds or thousands of images are collected routinely. To help us with image collection in our minirhizotron studies, we developed a mechanical handle that simplifies minirhizotron camera registration and image collection. The handle is attached to the minirhizotron camera and fits inside 6 cm, internal diameter, minirhizotron tubes. The handle couples a ratchet advancing mechanism with another mechanism that locks the handle to the minirhizotron tube, ensuring proper camera and tube registration. The ratchet mechanism advances the camera one camera field of view (frame) at a time. While the handle can be used to rapidly advance the camera, it is best to pause 2 to 3 s after each advance, to allow sufficient time for the image to be recorded on the video tape. At this rate, 20 to 30 frames can be recorded each minute. The camera, with handle attached, is easily moved from one minirhizotron tube to another. We conducted a simple study of handle performance and estimate that camera registration precision (a measure of relocating the camera in the same position) is >99%.