The invention describes a surface covering that comprises modules, made up of elements with irregular undulating edge, imitating natural warping of wood. When the wellbore pressure is reduced, at least a portion of the expandable fluid can vaporize, which can generate foam that aids in the formation andor enlargement of a cavity in the coal seam proximate the wellbore. Time-scale modification is applied separately to the individual frequency bands. A preferred embodiment uses a handheld computer to display GPS data, and can be expanded to also calculate and display depth and decompression data, and to provide for further expansion and integration to include other devices.