HydroGeoSphere/Grid Projection

Figure 5.5 illustrates the degree of distortion that can occur (which is especially severe at the poles) when a spherical geographic coordinate system, such as longitude and latitude, is mapped directly into a planar 2-D coordinate system. The following command can be used to correct the distortion which occurs when modelling large continental scale problems.

Project grid

 * 1) projt The projection type to be applied. Currently, the only valid inputs for projt are albers equal-area or lambert azimuthal equal-area, which apply the Albers conical or Lambert azimuthal equal-area projections respectively. For the Albers projection, the following additional data are required:
 * (a) lon0, lat0 The longitude and latitude for the origin of the projection.
 * (b) lat1, lat2 The latitude of the standard parallels.
 * (c) datum The datum used for the projection. Acceptable values for the variable datum are:
 * 1     Sphere.
 * 2     Ellipsoid (Clarke 1866).
 * For the Lambert projection, the following additional data are required:
 * (a) lon0, lat0 The longitude and latitude for the origin of the projection.
 * (b) datum The datum used for the projection. Acceptable values for the variable datum are:
 * 1     Sphere.

Transforms the current mesh from a spherical system into a planar 2-D coordinate system. It must be inserted just before the End grid generation command.

The following example uses the Project Grid instruction:

The grid produced by the Generate blocks interactive instruction is shown on Figure 5.5 and once projected, the grid looks like the one on Figure 5.6:




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Project 2d grid
The input data for this instruction is identical to that required for the Project grid instruction described above.

Transforms the current mesh from a planar 2-D coordinate system into a spherical system. It must be inserted just before the End grid generation command.
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Unproject 2d grid
The input data for this instruction is identical to that required for the Project 2d grid instruction described above.

Transforms the current mesh from a spherical coordinate system into a planar 2-D system. It must be inserted just before the End grid generation command.
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