GMS:Defining Layer Elevations: Difference between revisions
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When interpolating layer data for the purpose of [[GMS:Defining the Layer Elevations|defining MODFLOW layer elevation arrays]], there are often cases where the interpolated values overlap. For example, for some of the cells, the top elevation values for a particular layer may be lower than the bottom values for the layer. In some cases, the best way to fix such a problem is to experiment with the interpolation options or to create some "pseudo-points" to fill in the gaps between sparse scatter points. In other cases, the overlap may correspond to a pinchout or truncation in the layer. In such cases, the elevations need to be adjusted so that there is a small but finite thickness for all cells in the overlapping region. | When interpolating layer data for the purpose of [[GMS:Defining the Layer Elevations|defining MODFLOW layer elevation arrays]], there are often cases where the interpolated values overlap. For example, for some of the cells, the top elevation values for a particular layer may be lower than the bottom values for the layer. In some cases, the best way to fix such a problem is to experiment with the interpolation options or to create some "pseudo-points" to fill in the gaps between sparse scatter points. In other cases, the overlap may correspond to a pinchout or truncation in the layer. In such cases, the elevations need to be adjusted so that there is a small but finite thickness for all cells in the overlapping region. | ||
The first step in fixing layer errors is to use the [[GMS:Model Checker|Model Checker]] to determine if elevation overlaps occur. If they do occur, the Fix Layer Errors button at the top of the Model Checker dialog can be used to bring up the ''Fix Layer Errors'' dialog. The number of overlap errors for each layer is listed on the right side of the dialog. A layer is highlighted and a correction method is selected on the left side of the dialog. The '''Fix Selected Layer''' button is then used to adjust the elevations. Four options are available for fixing layer errors: | The first step in fixing layer errors is to use the [[GMS:Model Checker|Model Checker]] to determine if elevation overlaps occur. If they do occur, the '''Fix Layer Errors''' button at the top of the ''Model Checker'' dialog can be used to bring up the ''Fix Layer Errors'' dialog. The number of overlap errors for each layer is listed on the right side of the dialog. A layer is highlighted and a correction method is selected on the left side of the dialog. The '''Fix Selected Layer''' button is then used to adjust the elevations. Four options are available for fixing layer errors: | ||
===== Average ===== | ===== Average ===== | ||
With the Average method, for each cell where an overlap is found, the average elevation at the overlap is computed as | With the ''Average'' method, for each cell where an overlap is found, the average elevation at the overlap is computed as | ||
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===== Preserve Top ===== | ===== Preserve Top ===== | ||
With the Preserve top method, at each cell, where an overlap is found the top elevation is unchanged and the bottom elevation is adjusted to: | With the ''Preserve top'' method, at each cell, where an overlap is found the top elevation is unchanged and the bottom elevation is adjusted to: | ||
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===== Preserve Bottom ===== | ===== Preserve Bottom ===== | ||
With the Preserve bottom method, at each cell where an overlap is found the bottom elevation is unchanged and the top elevation is adjusted to: | With the ''Preserve bottom'' method, at each cell where an overlap is found the bottom elevation is unchanged and the top elevation is adjusted to: | ||
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===== Truncate to Bedrock ===== | ===== Truncate to Bedrock ===== | ||
The Truncate to bedrock option differs from the other methods in that it can be used to alter several layers at once. With this method, it is assumed that the bottom elevation values for the bottom layer represent the top of a bedrock unit. The bedrock elevations may overlap several upper elevation arrays. Each cell in the grid is checked and if the bedrock elevation is above the top elevation for the cell, the cell is turned off (made inactive). If the bedrock elevation is below the top elevation and above the bottom elevation for the cell, the bottom elevation for the cell is set equal to the bedrock elevation. If the bedrock elevation is below the bottom of the cell, the cell elevations are unchanged. | The ''Truncate to bedrock'' option differs from the other methods in that it can be used to alter several layers at once. With this method, it is assumed that the bottom elevation values for the bottom layer represent the top of a bedrock unit. The bedrock elevations may overlap several upper elevation arrays. Each cell in the grid is checked and if the bedrock elevation is above the top elevation for the cell, the cell is turned off (made inactive). If the bedrock elevation is below the top elevation and above the bottom elevation for the cell, the bottom elevation for the cell is set equal to the bedrock elevation. If the bedrock elevation is below the bottom of the cell, the cell elevations are unchanged. | ||
==Define Layer Data with Solids== | ==Define Layer Data with Solids== | ||
