Rather than arbitrarily correct the IMP results to match the soil sample results or vice varsa, it seemed appropriate to investigate some of the factors that contribute to the comparisons. TI. FACTORS INFLUENCING COMPARISONS There are -a number of factors that influence the comparison of soi] sample and IMP readings. Some of these are listed below and briefly discussed. 1. Background subtraction in 241 Am photopeak IMP readings. The back- ground subtraction routine in the IMP data reduction program consi- ders channels on both sides of the 241 ny photopeak. The influence of this routine in the calibration data as related to the actual field conditions should be investigated. 2. Soil Density. Does the fact of different soil densities affect the IMP and soil sample calibration? 3. 241 a, vertical distribution in the soil. What is the vertical distribution of 241 Am in the soil and how does this influence the “soil sample~IMP comparisons. 4, Field-of-View. Does the soil sampling procedure adequately sam- ple the IMP's field-of-view? Several items in this category are: a. Effect of rocks in the field-of-view. b. What is the variability from point to point? Are enough soil samples being taken? c. What is the effect of changing the sampling board and rope knots. d. What are the road way effects?