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Notes on the symbol descriptions
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- 15.3 Instructions for Symbolising Points
- 15.4 Instructions for Symbolising Lines
- 15.4.2 Direction of drawing the line
- 15.4.3 Laying out the symbols along the line
- 15.4.5 Symbols or Text for Lines
- 15.5.2 Centred Symbols for areas
- 15.6 Examples of Symbol Diagrams
15.2.2 Notes on the symbol descriptions* 'N/A' under 'look-up table affected' means "Not Applicable". ** 'Bounding box': in order to show the details clearly, many of the diagrams are enlarged over the true size, by as much as ten times for small symbols, with the result that the edges of the symbol sometimes overflow the bounding box (see for example symbol SY(BUISGL11)). This does not invalidate the drawing instructions. *** 'Comments':If an area is "transparent filled" the description means percentage given applies to the transparent part. Example: 75% transparency means that of four adjacent pixels, three are transparent. 15.2.3 Instructions on the symbol diagrams 'Line Weight', as used in the symbol descriptions, is equivalent to "line width". It is derived from the following requirement for screen resolution given in S-52, section 5.1 and repeated in IEC 61174 [7], clause 5.8.2: "Minimum lines per mm (L) is given by L = 864/s, where s is the smaller dimension of the chart display area (e.g. for the minimum chart area, s = 270 mm and the resolution is L = 3.20 lines per mm, giving a "Picture Unit" size of 0.312 mm)." The term 'Picture Unit' used above is the general form of the earlier concept of pixels of about 0.3 mm size. Hence a Line weight of 0.3 mm represents a line or dot of one-pixel width; a line weight of 0.6 mm represents a two-pixel line or four-pixel dot, and so on. 15.3 Instructions for Symbolising Points15.3.1 Reference to PresLib ManualPlease read section 9, particularly: 9.2 on symbol rotation (note particularly "Symbols with no rotation shall always be drawn upright with respect to the screen borders"). Contour labels shall be drawn upright, for ease of reading, not aligned with the direction of the contour as on the paper chart. 9.4 and 9.2 on area symbolisation by a centred symbol, and symbol offsets. 15.4 Instructions for Symbolising Lines15.4.1 Reference to PresLib ManualLinestyles symbolise (a) line objects such as routes and (b) area boundaries. There are two types of line styles, simple linestyles and complex linestyles. Please read sections 8 and 9, particularly: 8.2 on the usage of complex linestyles, 9.3 on line symbology in general, 9.3 on the "predefined line style", i.e. the simple linestyles.
Some complex linestyles are 'directional', either to indicate the direction of traffic in a route or to define the inside of an area by the foot of 'T' or 'V' symbols built into the line. Whereas point symbols and centred area symbols may be oriented by means of the ORIENT attribute, directional linestyle symbols are always oriented in the direction of the digitised line they represent. It is essential that the direction of drawing lines coincides with the direction of digitising of the line in the ENC (that is in the direction of a one way traffic route or track, or clockwise around an area). Examples are given in the following table using LC(DWRTCL07) and LC(ENTRES51):
15.4.3 Laying out the symbols along the lineThe pivot point determines the spacing between individual symbols of the complex linestyle. The pivot point of the first line symbol shall be placed on the start of the line and the pivot point of each successive symbol shall be placed on the end of the preceding symbol (see section 8.2). 15.4.4 Curved LinesIn order to fit all digitised lines (including curved lines), the complex linestyle is designed to bend around curves (for example, in order to symbolise the boundary of a circular anchorage area.) If the curve is too sharp for the ECDIS to follow the digitised line exactly for part, or all, of the run-length of the line, the linestyle shall default to a dashed line of the same colour and lineweight as the original line style symbol (see section 8.2). 15.4.5 Symbols or Text for LinesThe pivot point of symbols or text associated with a line shall be located at the midpoint of the run-length of the line (see section 9.1). 15.5 Instructions for symbolising areas15.5.1 Reference to PresLib ManualAreas are symbolised (a) by boundary linestyles (if the look-up table for symbolized boundaries is used); (b) by centred symbols; (c) by colour fill; or (d) by special area fill patterns. See section 8.4. 15.5.2 Centred Symbols for areasThe pivot point of centred symbols shall be located at or near the centre of gravity of the area displayed. See section 8.5 for details. 15.5.3 Pattern spacing for area fill patternsIt is critically important to maintain the correct spacing between the symbols of certain area fill patterns. For example too wide a spacing between the grey dots of AP(DRGARE01) will effectively make the pattern invisible, while too close a spacing will cause clutter. Another example: the difference between the open spacing of the grey dashes of AP(PRTSUR) and the closely spaced dashes of AP(NODATA03) symbolizes the difference between a partly surveyed area with little data and an unsurveyed area with no data at all. 15.6 Examples of Symbol DiagramsExamples for a point symbol SY(ACHARE51), a line symbol LC(ACHARE51) and an area symbol AP(RCKLDG01) are given below: a) Point Symbol Symbol Name: SY(ACHARE51) RN: 2 Symbol Explanation: anchorage area
area symbols with symbolized boundaries Pivot Point Column: 6.29 Pivot Point Row: 7.79 Width of Bounding Box: 12.29 Height of Bounding Box: 13.04 
Symbol Colours: CHMGF Comments: Line weight 0.3 mm Examples on ENC: N/A References:
b) Line Symbol Symbol Name: LC(ACHARE51) RN: 469 Symbol Explanation: boundary of an anchorage area
Pivot Point Row: 2.42 Width of Bounding Box: 30.30 Height of Bounding Box: 5.03 
Symbol Colours: CHMGD Comments: Line weight 0.3 mm; Anchor symbol dimensions like point symbol ACHARE02 Examples on ENC: N/A References:
c) Area Symbol Symbol Name: AP(RCKLDG01) RN: 464 Symbol Explanation: rock or coral drying ledges
Pivot Point Row: 13.38 Width of Bounding Box: 15.41 Height of Bounding Box: 13.32 
Symbol Colours: LANDF Pattern Type: Linear Pattern Spacing: Constant Minimum Distance: 0.00 Maximum Distance: 0.00 Comments: Line weight 0.3 mm The seven “v” symbols in the box illustrated shall form a continuous uniform pattern over the area of the object being symbolized. Examples on ENC: N/A References:
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