globalmapper.GenerateRoughnessGrid
==================================

.. currentmodule:: globalmapper
.. py:function:: GenerateRoughnessGrid (GM_LayerHandle_t32 aLandCoverLayer, GM_RoughnessGridParams_t aGridParms, int aReserved) -> GM_Error_t32, GM_LayerHandle_t32

    Generates a roughness length grid from the provided raster land cover layer. The returned layer handle must be
    closed with :doc:`CloseLayer<../load/globalmapper.CloseLayer>` when you are done with it. It will be an "elevation"
    grid layer so any elevation related functions will work on it. The roughness values are generated based on a
    provided table of land cover to roughness length values to use.

    There are several built-in roughness tables, but if you have provided a roughness_tables.txt file in your
    application folder then you can provide that roughness table. The first roughness table in that file will have an
    index of GM_Roughness_NumTypes with subsequent custom tables increasing by one.

    :param GM_LayerHandle_t32 aLandCoverLayer: Raster land-use Layer to generate roughness from
    :param GM_RoughnessGridParams_t aGridParms: Parameters for generating roughness grid
    :param int aReserved: Reserved for future use; must be 0.
    :returns: Error Code
    :rtype: GM_Error_t32
    :return: Created roughness grid layer
    :rtype: GM_LayerHandle_t32