How the drawings are checked

A symbol library is only as good as its drawings, and a drawing can be wrong in ways no unit test sees: a path whose numbers ran together, an icon a few per cent off centre, a letter in the wrong font. Every drawing here is checked against the standard's own plates.

Against the plates

Each standard's plates are cropped from the document, and every icon is drawn beside its plate:

• Scored. The plate's octagon guide gives scale and position; our icon is drawn to the same octagon and the dark pixels compared both ways. 2525E's 972 scored icons have a median of 1.00; 2525D's 990, 0.99; 2525C's 1,114 letter codes, 0.97.
• Placed. The shift at which drawing and plate overlap best is measured rather than scored within a tolerance. Drawings the plates put elsewhere, or at another size, are corrected, each with its measurement.
• Anchored. Every point control measure's anchor is checked against the anchor arrow of its Appendix L template, and every point's field letters are placed where its template has them.
• Read by eye. The lowest scores are a ranking, not a verdict: each is looked at beside its plate. A plate cut by its cell, a label in the example, a hairline frame are noted, not "fixed".

Against each other

• No two codes draw alike without a reason. Every code of every standard is drawn; codes whose drawings are identical fail the check unless the standard itself draws them alike.
• The canvas is the SVG. drawSymbol is compared with the browser's own rendering of the SVG, pixel by pixel, over every code.
• The map is the SVG. The glyph the map renderers draw is compared with the SVG, so a fill rule or a hole the map would lose is caught.

What the standard leaves open

Where the standard is silent the choice is the library's, and it is written down where it is made: the frame for a signals intelligence symbol of no stated dimension, where the exercise letter sits, the operational condition bar's depth. One weight for every frame line, in every standard, is one such choice: the standards set no number, and the drawings' own weights differed.