Refs with dual numeral systems

[claysmalley]

Some countries have route shields posted with local numeral systems alongside Western Arabic numerals. These could potentially be displayed side-by-side, or one at a time with language switching (#21).

For example, Iran (#463, #464) posts Persian numerals:

In the case of Iran, the route relations are tagged with Western Arabic numerals in ref=* and Persian numerals in ref:fa=*. Only ref=* is surfaced in OpenMapTiles, and none of the available fonts have glyphs for Persian numerals. These issues would need to be resolved before support can be added for Persian numerals on Iranian highways.

[1ec5]

Saudi Arabia posts its route numbers only in Eastern Arabic numerals, but currently they’re tagged only in Western Arabic numerals: #467.

[1ec5]

For some ROC shields, we’re showing Chinese characters instead of the corresponding alphabetic suffixes because that’s what’s in the vector tiles: #141 (comment).

[1ec5]

In addition to numeral systems, some refs contain homoglyphs. For example, in Greece, we display shields for E roads using the Latin “E” but motorways using the Greek “Α” and national roads using the Greek “ΕΟ”.

Meanwhile, in Belarus, many routes have been mistagged with “false friend” homoglyphs, such as the Latin “P” instead of the Cyrillic “Р” that corresponds to the Latin “R”, or the Latin “H” instead of the Cyrillic “Н” that corresponds to the Latin “N”. This is currently tripping up some navigation software.

For Americana, homoglyphs probably don’t make a huge difference, since we’re relying on network values that spell out the intended network in English to choose a shield background image. However, it’s a good argument for expecting the relations to be explicitly tagged with the route numbers in each writing system if so desired, rather than relying on automated transliteration on the client side.

[claysmalley]

Highways in Iraq are signed with both Western and Eastern Arabic numerals: #557