# HydroGeoSphere/Elevation Instructions

These instructions are used to define 3-D mesh base elevations and new layer top elevations.

## Elevation constant

1. elev Elevation value [L].
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## Elevation from gms file

1. basefile Name of the data file containing the elevation values for each node in the 2-D grid. This is a string variable. The file should be formatted as outlined in Section F.2.
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## Elevation from gb file

1. basefile Name of the data file containing the base elevation values for each node in the 2-D grid. This is a string variable. The file should be formatted as outlined in Section G.2.
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## Elevation from raster file

1. rasterfile Name of the raster file containing the base elevation values. This is a string variable. The file should be formatted as outlined in Section H.
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## Elevation from bilinear function in xy

1. xfrom, xto, yfrom, yto x- and y-ranges.
2. a1,a2,a3,a4,a5 Constants for bilinear function.

For nodes falling within the given x- and y-range, the z-coordinate is computed according to the following function:

$z=a1+a2(x-\mathbf {xfrom} )+a3(x-\mathbf {xfrom} )^{2}+a4(y-\mathbf {yfrom} )+a5(y-\mathbf {yfrom} )^{2}$ • • •

## Elevation from sine function in xy

1. xfrom, xto, yfrom, yto x and y ranges.
2. zz0 Elevation at xfrom, yfrom.
3. num_sw_x,amplitude_x,slope_x Number of sine wave cycles, sine wave amplitude and surface slope in the x−direction.
4. num_sw_y,amplitude_y,slope_y As above but in the y−direction.

For nodes falling within the given x- and y-range, the z-coordinate is computed according to the following function:

$z=\mathbf {zz0} +\mathbf {amplitude\_x} (1+\sin(f(x)))+\mathbf {slope\_x} (x-\mathbf {xfrom} )+\mathbf {amplitude\_y} (1+\sin(f(y)))+\mathbf {slope\_y} (y-\mathbf {yfrom} )$ where:

$f(x)=(x-\mathbf {xfrom} )/(\mathbf {xto} -\mathbf {xfrom} )\ast 2{\pi }\ast \mathbf {num\_sw\_x}$ $f(y)=(y-\mathbf {yfrom} )/(\mathbf {yto} -\mathbf {yfrom} )\ast 2{\pi }\ast \mathbf {num\_sw\_y}$ • • •

The number of cycles of the sine wave can be a fraction and the sine function rises from a value of $\mathbf {zz0}$ at $(\mathbf {xfrom} ,\mathbf {yfrom} )$ as x- and y-values increase. Where the peaks coincide, the maximum elevation is the sum of $\mathbf {zz0} +\mathbf {amplitude\_x} +\mathbf {amplitude\_y}$ .

## Elevation from cosine function in xy

As above but uses the cosine function instead of the sine function.

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## Elevation from xz pairs

1. xval, zval xz-pair 1.
2. xval, zval xz-pair 2.
3. ...etc...
4. xval, zval xz-pair n.
5. end Signals end of list.

Listed xz-coordinate pairs are read until an End instruction is encountered. They should be given in order from smallest to largest x. For each node in the 2-D grid, the x-coordinate of the node is used to determine its position in the list, and a z-coordinate is then interpolated from the neighbouring xz-pairs.

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