# HydroGeoSphere/Elevation Instructions

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

## Elevation constant[edit | edit source]

**elev**Elevation value [L].

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## Elevation from gms file[edit | edit source]

**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[edit | edit source]

**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[edit | edit source]

**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[edit | edit source]

**xfrom, xto, yfrom, yto***x*- and*y*-ranges.**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:

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## Elevation from sine function in xy[edit | edit source]

**xfrom, xto, yfrom, yto***x*and*y*ranges.**zz0**Elevation at**xfrom**,**yfrom**.**num_sw_x,amplitude_x,slope_x**Number of sine wave cycles, sine wave amplitude and surface slope in the*x*−direction.**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:

where:

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The number of cycles of the sine wave can be a fraction and the sine function rises from a value of at as *x*- and *y*-values increase. Where the peaks coincide, the maximum elevation is the sum of .

## Elevation from cosine function in xy[edit | edit source]

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

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## Elevation from xz pairs[edit | edit source]

**xval, zval***xz*-pair 1.**xval, zval***xz*-pair 2.**...etc...****xval, zval***xz*-pair n.**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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