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2020-12-18 23:34:01 +03:00
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< h1 > < a class = "header" href = "#ab-streets-map-model-as-a-platform" id = "ab-streets-map-model-as-a-platform" > A/B Street's map model as a platform< / a > < / h1 >
< p > A/B Street's representation of a city, built mostly from OSM and lots of
heuristics, is likely useful to other projects. This doc brainstorms what it
would look like to properly expose it to other users.< / p >
< p > To sum up what the map model provides: geometry + semantics.< / p >
< h2 > < a class = "header" href = "#use-cases" id = "use-cases" > Use cases< / a > < / h2 >
< ul >
< li > Different UIs (particularly 3D / VR) for exploring cities as they are or as
they could be, like Streetmix 3D and Complete Street Rule< / li >
< li > Importing slices of a city as assets into a game engine like Godot
< ul >
< li > Imagine a hackathon where people easily build games based on the real world< / li >
< li > Like < a href = "https://developers.google.com/maps/documentation/gaming/overview_musk" > https://developers.google.com/maps/documentation/gaming/overview_musk< / a >
but open< / li >
< / ul >
< / li >
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< li > A new OSM viewer/editor, particularly focused on POIs< / li >
< li > Something focusing on 15-minute neighborhoods, with isochrones and nearby
amenities< / li >
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< / ul >
< p > TODO: Give a quick Python example of what interacting with the end goal could
look like.< / p >
< h2 > < a class = "header" href = "#just-data-is-not-enough" id = "just-data-is-not-enough" > Just data is not enough< / a > < / h2 >
< p > At first glance, the existing < code > Map< / code > structure could be written to some format
with a nicely documented schema. This would certainly be useful, but it's not
nearly enough. Interpreting the data sometimes requires lots of code, which
already exists -- so why not expose it to users as well?< / p >
< p > Examples in OSM where I wish " standard libraries" existed to interpret the data:< / p >
< ul >
< li > The simple task of detecting intersections between ways< / li >
< li > < a href = "https://github.com/dabreegster/abstreet/blob/master/map_model/src/make/initial/lane_specs.rs" > Figuring out what lanes a road has from tags< / a > < / li >
< li > Gluing multipolygons together< / li >
< li > Inferring turns at an intersection, subject to the several types of turn
restrictions< / li >
< / ul >
< p > A/B Street solves these problems (or at least it tries to), but by itself, the
resulting data isn't always useful. So some examples of where a library would be
needed too:< / p >
< ul >
< li > Pathfinding. ABST does lots of work especially to handle " live" map edits and
cheaply regenerate contraction hierarchies. Also, pathfinding requires obeying
OSM turn restrictions that span multiple roads -- this prevents even plain old
Dijkstra's from working correctly.< / li >
< li > Getting geometry in different forms. Lanes are stored as a < code > PolyLine< / code > , but
what if a consumer wants the thickened < code > Polygon< / code > , either as points, or maybe
even pre-triangulated vertices and indices?< / li >
< / ul >
< h2 > < a class = "header" href = "#how-would-an-apilibrary-work" id = "how-would-an-apilibrary-work" > How would an API/library work?< / a > < / h2 >
< p > The traditional approach is to link against part of A/B Street as a library and
call it through language-specific bindings. The more language-agnostic option is
defining an API (maybe JSON or protobuf) and having clients run a local A/B
Street server, making HTTP requests to it. This is like the " sidecar" pattern in
microservice-land.< / p >
< h2 > < a class = "header" href = "#compatibility" id = "compatibility" > Compatibility< / a > < / h2 >
< p > Really have to think through this carefully. Some examples of big changes on the
horizon:< / p >
< ul >
< li > Additive: separate cycleways and tramways. Likely no schema change.< / li >
< li > Modify: traffic signals will get
< a href = "https://github.com/dabreegster/abstreet/issues/295" > more complex< / a > < / li >
< li > Modify: we'll likely try again to merge tiny intersections together, which
would get rid of the current guarantees that a road/intersection is associated
to one particular OSM object< / li >
< / ul >
< h2 > < a class = "header" href = "#layering" id = "layering" > Layering< / a > < / h2 >
< p > Clients should be able to opt into different data layers. For example, A/B
Street strips out OSM building tags right now to keep filesizes small. But an
OSM viewer would want to keep this (and likely discard the large contraction
hierarchies). So some pieces of the map model need to be teased apart into
optional pieces, and probably loaded in as separate files.< / p >
< h2 > < a class = "header" href = "#the-bigger-vision" id = "the-bigger-vision" > The bigger vision< / a > < / h2 >
< p > Depending what other open source projects are on board, the general idea is to
start assembling an ecosystem of libraries/tooling to make it easier to build
new things off of open GIS data.< / p >
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< p > The end state might look like this. A few separate applications would exist, all
running both natively and in the browser:< / p >
< ul >
< li > A/B Street the game, more or less in its current form< / li >
< li > A new OpenStreetMap viewer, likely focused on visualizing roads and
points-of-interest in detail< / li >
< li > The street parking OSM editor, and other OSM editors specialized for mapping
certain things< / li >
< li > A new app focusing on 15-minute neighborhoods, using isochrones to show
amenities available nearby
< ul >
< li > Ideally, allow editing current land use / zoning, to let people explore how
new policies might get closer to a 15-minute neighborhood.< / li >
< li > Possibly < a href = "https://www.open-accessibility.org" > GOAT< / a > does all of this
already, and this new thing shouldn't be built< / li >
< / ul >
< / li >
< li > A new app for creating story maps, showing events that occur over time, with
lots of detail about the surrounding environment< / li >
< / ul >
< p > All of these would make use of some common libraries, which should be extracted
out cleanly from A/B Street today:< / p >
< ul >
< li > the map model and OSM importer< / li >
< li > the widgetry UI library< / li >
< li > some common code for specifically interacting with maps in widgetry< / li >
< li > a tool to generate a traffic demand model from OSM data, optional census data,
etc
< ul >
< li > This has been initially
< a href = "https://dabreegster.github.io/abstreet/trafficsim/travel_demand.html#proletariat-robot" > prototyped< / a > < / li >
< / ul >
< / li >
< li > the discrete-event traffic simulation that A/B Street uses today< / li >
< li > core geometry/utility libraries< / li >
< / ul >
< p > But note only the first application would use things like the simulation
library. The point of more cleanly modularizing these pieces is to make it
easier for new people to build different pieces, without having to understand
and be coupled to everything else. Also, as appropriate, these pieces should use
common data formats (like
< a href = "https://github.com/d-wasserman/shared-row/" > shared-row< / a > ) to be interoperable
with Streetmix, Complete Streets, etc.< / p >
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