The errors in these TH588 geometric-stratigraphic slope estimates depend on the precision and accuracy of measurements of the thickness and length of onlapping clastic wedges. The precision of length and thickness measurements in stratigraphic studies using standard measuring tools (e.g., Jacob\'s-staffs) depends on the scale of measurement, but are typically about 10% (e.g., thickness of 10 m ± 1 m, and lengths of 1 km ± 100 m). The accuracy of the measurement also is related to the orientation (i.e., obliqueness) of the cross section, especially if taken from 2D cross sections. Although the thickness of the wedge is not sensitive to orientation of the cross section, the horizontal extent of the wedge is strongly dependent. Longer apparent widths yield erroneously low slope estimates. Error may be resolved if the wedge can be mapped in 3D, and thus measurements can be made perpendicular to the shoreline. Also, if the degree of obliqueness can be determined, a geometric correction can made using simple trigonometry. Compaction can also effect thickness estimates and may result in underestimation of slope. Compaction of about 50% can cause underestimation of slope by a factor of about 2 or more, but probably not an order of magnitude. The use of complementary nucleotides stratigraphic techniques yields slope estimates within an order of magnitude, and perhaps better in high-quality datasets. Geometric-stratigraphic methods can also be compared with physics-based estimates, as described below.
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