Marching Squares Algorithm

Marching squares is a computer graphics algorithm that generates contours for a two-dimensional scalar field arranged as a rectangular array of values, producing either isolines that follow a single data level or isobands that fill the area between isolines. It processes each cell of the grid independently, computes a cell index by comparing the contour level with the values at the cell's four corners, uses a pre-built lookup table keyed on that index to determine the output geometry, and applies linear interpolation along the cell boundaries to place the contour precisely. Typical applications include the contour lines on topographic maps and the isobars on weather maps.