Total ground-cover estimates from corrected scene brightness measurements

Total ground-cover estimates from spectral reflectance data were studied using a scene brightness factor, corrected for variations in soil moisture content. Red and near-infrared radiometer readings were collected from ground level on a bermudagrass [Cynodon dactylon (L.) Pers.] rangeland in south Texas. A soil line was developed to obtain brightness factor and correction factor values that were correlated to total ground-cover measurements. Data were collected under two conditions: (1) when the soil was dry and vegetation senescent, and (2) under wet soil and green vegetation conditions. Although the correction factor did not improve the correlation between brightness measurements and total ground cover, overall correlations were high. The best correlation (r = 0.87) was obtained when vegetation was near peak greenness and the soil was saturated. This study suggests that under certain conditions scene brightness measurements can provide relatively accurate total ground-cover estimates.