RADAR - RAdio Detection And Ranging
Category: - Maritime - Acronym

Radio Operator - An officer who operates and controls the shipboard communication equipment.
Category: - Maritime

Rail - The upper rounded edge of the bulwarks.
Category: - Maritime

Rainbow - Rainbows occur when sunlight is refracted and then reflected by raindrops. The raindrops act like a prism, breaking the light into the colours of a rainbow, with red on the outer, and blue on the inner edge. On occasion the light can be reflected from both the front and back of the raindrops and two rainbows are visible, with the colour bands in the second opposite to those in the primary rainbow. Rainbows can be seen when the sun is shining and the air contains water spray or raindrops. This condition occurs frequently during or immediately following showers. Rainbows are always observed in the portion of the sky opposite the sun. The sun, the observer's eye, and the centre of the rainbow arc, always fall on a straight line.
Category: - Weather

Rake - Slope aft of a mast, king post or stack.
Category: - Maritime

Ramp (Or Strip) Alert - An increased standby posture maintained by Canadian Forces search and rescue forces during periods of increased or notable activity. "alerte « aire de trafic » ou « piste d’envol »"
Category: - SAR

Random - Having no discernible structure or repetition.
Category: - GIS

Range - The highest value of an attribute less the lowest, in the unit of the attribute.
Category: - GIS

Range Lights - A set of two small lighthouses, aligned so that if a vessel lines them up, they will be guided safely into a harbour, through narrow channels.
Category: - Maritime

Raster - A data structure for maps based on grid cells.
Category: - GIS