Mapping of calcium carbonate equivalent and clay content of surface soil using geostatistical methods (Case study: Chitgar park, Tehran)

In recent decades, remote sensing methods because of their economical aspects are frequently used in soil survey studies. The objective of this study was to compare the remote sensing and geostatistical methods for estimating and mapping the calcium carbonate equivalent and clay content of surface soil in the Chitgar Park with the area of 665 hectares. Therefore, 116 samples (0-20 cm) were taken by the intervals of 250 meters based on regular grid patterns. Two geostatistic methods of kriging and inverse distance weighting (IDW), and two remote sensing techniques of near-infrared analysis (NIRA) and Continuum removal (CR) were used for modeling the desired variations. The results of the cross validation showed that the accuracy of kriging was appropriate for modeling clayand calcium carbonate equivalent contents. The NIRA method due to the low correlation between TM bands and calcium carbonate equivalent was not validated for modeling the calcium carbonate equivalent; but this method was appropriate for estimating clay content (R2=0.52). CR method was not accurate for both variables of clay and calcium carbonate equivalent. Based on the overall accuracy and Kappa coefficient of producing maps, it is concluded that the kriging method has higher accuracy than remote sensing methods. Although high accuracy of geostatistic methods is expected due to the use of real data, the acceptable accuracy of the NIRA technique for modeling the clay variable should be considered with respect to lower costs of remote sensing methods.