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===Baselap and truncation===

===Baselap and truncation===

For computer mapping, the term ''baselap'' can be defined as the abrupt termination of a higher surface (usually depositional) against a lower surface. A similar definition could be used for ''truncation''—the abrupt termination of a lower surface against a higher surface (usually an unconformity).

For computer mapping, the term ''baselap'' can be defined as the abrupt termination of a higher surface (usually depositional) against a lower surface. A similar definition could be used for ''truncation''—the abrupt termination of a lower surface against a higher surface (usually an [[unconformity]]).

Most computer mapping systems build a surface model using only data for that surface. When one surface laps onto or truncates another, the initial surface models will almost always cross ([[:file:using-and-improving-surface-models-built-by-computer_fig8.png|Figure 8]]). This is expected and must be corrected. The following discussion describes methods for handling baselap and truncation in a grid-based mapping system.

Most computer mapping systems build a surface model using only data for that surface. When one surface laps onto or truncates another, the initial surface models will almost always cross ([[:file:using-and-improving-surface-models-built-by-computer_fig8.png|Figure 8]]). This is expected and must be corrected. The following discussion describes methods for handling baselap and truncation in a grid-based mapping system.