<b>Description</b><br/>A <b>VerticalLayer</b> describes the vertical dimension, either downwards in the soil, or upwards in a crop canopy.<br/><br/><b>Remark.</b><br/>In a crop canopy the zero plain is always the soil surface. <br/>In the soil, the layer can be described in respect of the soil surface, but eventually also in respect of the Z plain of the used coordinate system.<br/>The expression "Vertical" is added to prevent confusion with a map layer.<br/>