Geographic data represents real world phenomena that can be measured at locations on Earth. It can describe discrete objects with boundaries or continuous fields without clear boundaries. Geographic data is represented digitally using data models like raster and vector structures. Vector data represents discrete objects while raster data divides space into a grid. Topology defines spatial relationships between geographic features that is important for analysis. Sampling and interpolation are used to generalize and estimate values across continuous surfaces from a finite set of sample points.