Raster Chart

A digital chart made from a georeferenced image of a paper nautical chart.

A raster chart preserves the printed chart’s appearance as a grid of pixels. Navigation software can place the vessel’s position and other overlays on the image, but the individual symbols, soundings and lines are not separate selectable objects as they are on a vector chart.

Zooming beyond the chart’s intended scale enlarges the pixels without adding detail and can make information appear less clear or more accurate than it is. The chart’s edition, corrections, scale, datum and source authority must therefore be checked just as they would be for the corresponding paper product.