Ref should be dropped in favor only of network and shield_text

[nvkelso]

Now that we're relying on network and shield_text (see #966) to do the heavy lifting instead of ref, we should probably drop ref from low- and mid-zooms (or maybe entirely) and modify merge logic to use the shield bits instead.

Probably only the singular network and shield_text at zooms 0-8 and at 9+ all_networks and all_shield_texts.

Example:

# Way: I 81 (302933871)
# http://www.openstreetmap.org/way/302933871
# Example tile: `14, 4496, 6381` in **roads** layer.

[nvkelso]

• What map location are you having problems with? near 10/36.9543/-81.0022 in tile 10/281/398
• Screenshot?

type: "MultiLineString",
properties: {
kind: "highway",
network: "US:I",
sort_key: 383,
kind_detail: "motorway",
source: "openstreetmap.org",
all_networks: [
"US:I",
"US:US"
],
shield_text: "81",
ref: "I 81;US 11",
id: 172243650,
all_shield_texts: [
"81",
"11"
]

(ignore the sidewalk bit in the screenshot)

[nvkelso]

In that same tile, here's a counter example where the ref contains data the network and shield_text lack:

properties: {
kind: "major_road",
network: "US:US",
sort_key: 380,
kind_detail: "primary",
source: "openstreetmap.org",
shield_text: "21",
ref: "US 21;US 52"
},

[nvkelso]

There's so many roads that only have ref values and no network relations in Europe we shouldn't do this in v1.

[nvkelso]

If tile file size is an issue after #1172 let's pull this one into v1.1 milestone.

[nvkelso]

We can't drop ref entirely (that'd be a 2.0 breaking change), but the rest of the description is still valid.

[zerebubuth]

It looks like we already drop ref on kinds:

• major_road between zooms 0 and 6 inclusive,
• minor_road between zooms 0 and 13 inclusive,
• rail between zooms 0 and 14 inclusive,
• path between zooms 0 and 11 inclusive.

Is that good enough for now? Or shall we try pushing the major_road zoom level down to 9 or something?

[nvkelso]

Doesn't seem like much of an issue. Let's address this in v2.0 when we strip off ref entirely in favor of network and shield_text.