Image analysis compared with other methods for measuring ground cover

Ground cover is a key indicator of rangeland health but conventional methods for measuring ground cover are labor intensive. Analysis of digital images has the potential to reduce ground-cover-measurement labor requirements. We compared cover measurements by image analyses of digital images (sensor resolution =0.97 mm/ pixel ground sample distance) with measurements derived from a laser point frame, and from two transect methods. We found there was low agreement in plot-to-plot comparisons but results were usually not different when averaged over a large number of plots or transects. We conclude that image analysis of large numbers of samples (images) produce mean values not different from conventional field methods, and, that image analysis is a superior choice for detecting relative change, since it facilitates greater data collection, reduces human bias by limiting human judgments, and provides a permanent record in images that can be retained for future scrutiny.