In this format, each cell is assigned a value based on surrounding elevation points. This gives the data an even and continuous distribution, resulting in a smooth surface when displayed. The grid or cell-based format also provide the best platform for analysis. Grids can be compared to show spatial, temporal, and volumetric change. Contours are isolines of elevation with a specified interval.
Contours provide an effective way of showing gradient change.
The closer the isolines are to each other, the steeper the elevation or beachface. For example, grid data can provide detailed information about volumetric and surface changes on a beach. This is useful in understanding sediment movement after a renourishment project. The study area represented above is a small section of the North Myrtle Beach renourishment project that took place from September 1996 through May 1997. Using a GIS software package, a difference grid can be created by subtracting two grids from one another.