A RASTER CHART
Is basically just a visual scan of a paper chart. It is a computer based system which uses charts issued by, or under the authority of, a national hydrographic office, together with automatic continuous electronic positioning, to provide an integrated navigational tool.
RASTER CHARTS are digitized by “scanning” the paper chart (using technology common in desktop publishing). Each tiny segment of each line on a chart is converted to a “raster” picture element or “pixel”. These pixels are similar to a television picture or magnified newsprint in that they appear as “dots” on a grid. That is where the raster chart stops: the pixels form images on a computer screen, but the computer is “dumb” about what the images mean.
A digital representation of a paper chart in a matrix-like scheme of pixels. This chart is created by scanning a paper chart
A VECTOR CHART
Is more complex. Each point on the chart is digitally mapped, allowing the information to be used in a more sophisticated way, such as clicking on a feature (for example, a lighthouse) to get all the details of that feature displayed.