Bending geographic maps for enhanced railway space-time diagrams

OuestWare

dataviz web apps at

I develop

and since early 2021

we work for

to contribute to

Open Source Railway Designer

at some point

we've been tasked to

enhance

the Space-Time Diagrams

...or Circulation Diagrams

Space-Time Diagrams

...or Train Graphs

what are

...or Graphical Timetables

to be the cover of a

a good enough graphic

even better

but this chart is actually

once we introduce

blocks

A quick word about blocks

in

in OSRD

can we make it

even more informative?

a schematic strategy

requires to know the exact topology

👍

allows rendering exactly what we want/need

👎

a cartographic strategy

we show everything a map would show

👍

we show everything a map would show

👎

it's called Strip maps

and it's actually been used with space-time diagrams already!

so...

let's bend geographic maps

generate a triangles grid

the strategy is to

along the path

and another straight grid

and to translate coordinates between the grids

here's our initial path

we build a grid along the path

we smoothen the grid

we index the grid, and

generate a straight similar grid

we have a projection \o/

For a given point P

  1. Find the quad that contains P
  2. Find the triangle T (indexed in the quad) that contains P
  3. Find the related triangle T' in the straight grid
  4. Transpose coordinates from T to T' to obtain P', using barycentric coordinate system

So, to get a map

Using react-map-gl and MapLibre

  1. Render a hidden map that contains the full grid (with layers from OSM and OSRD)
  2. Wait for every features to be rendered (the map's "idle" event)
  3. Query all the rendered features (with map.querySourceFeatures)
  4. Project every features
  5. Render a new map with the projected features

the two maps side by side

how it looks like in OSRD

we lose zoomable data

it is quite slow atm

👍

it works for almost any path

it does bring context

👎

(demo time)

thanks!

FOSDEM 2024 - Railways and Open Transport devroom

By Alexis Jacomy

FOSDEM 2024 - Railways and Open Transport devroom

Bending geographic maps for enhanced railway space-time diagrams

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