Explanation of Raster Chart (RNC) and Vector Chart (ENC).

 Raster Navigational Charts (RNCs) and Electronic Navigational Charts (ENCs) are the two types of charts used in ECDIS¹²³:

1. Raster Navigational Charts (RNCs): RNCs are a direct copy or a scan of the paper charts¹³. They look identical to a paper chart as all the information shown is directly printed³. The chart only grows larger or smaller as per the zooming and when rotated, everything rotates³. RNCs are simply an electronic image of a paper chart¹. They are digitized by scanning the paper chart and converting each line to a raster picture element or “pixel”¹. Beyond geo-referencing (positioning the scanned chart so that it appears in the right location with correct x and y coordinates), there is no intelligence or extra data in the raster image¹.

2. Electronic Navigational Charts (ENCs): ENCs are computer-generated charts¹³. They are “smart charts”, which means the user can click on different features, such as a light or buoy, to retrieve additional information not available in paper or raster charts¹. For example, a wharf appears only as an image on an RNC, but an ENC can identify it as a wharf and attach attributes to it such as height, length, age, ownership, number of berths, etc¹. This additional data, which is contained directly within the ENC, might otherwise only be available by consulting the relevant Sailing Directions publication¹. ENCs used on an Electronic Chart Display and Information System (ECDIS) and integrated with other data such as GPS position, radar, planned routes, heading, speed, and draught, assist mariners and alert them to sailing hazards, warnings, and dangerous situations¹. ENCs are powerful and flexible navigational tools that provide users with more control over the display of the chart¹.