抄録
Landsat Thematic Mapper (TM) data, collected in May 1984 and 1985, was used to estimate and map the gravelly layer's depth in upland soil. The values from the gravelly layer measured at 30 upland-soil locations in the study area (southern part of Tokachi district) were used for regression analysis with TM spectral data consisting of seven bands. It was found that band 2, band 4, band 5 and band 7 could be used effectively for estimating the gravelly layer's depth in upland-soil ; the respective correlation coefficient was higher in 1985 than that in 1984. This relationship was confirmed at 12 upland-soil locations in an area different (northern part of Tokachi) from the study area, where the correlation coefficient was 0.995 between estimated values and measured values. Therefore, the following experimental equation was obtained, using the values from the gravelly layer at 42 locations, and used for mapping the gravelly layer's depth in upland soil in the Tokachi district : Y=4.565TM2_<85>-5.754TM4_<85>+6.265TM5_<85>-6.417TM7_<85>-126.85(R=0.972, R^2=0.944, N=42). Where, Y is the gravelly layer's depth (cm) in upland soil and TM2_<85>, TM4_<85>, TM5_<85> and TM7_<85> are CCT (computer-compatible tape) counts of band 2, band 4, band 5 and band 7 in 1985, respectively. The gravelly layer's depth was divided into six levels for mapping (0.25-7.5 cm, 7.6-15.0 cm, 15.2-25.0 cm, 25.2-35.0 cm, 35.2-45.0 cm, 45.2cm-).
