Consectetur adipiscing elit
à portée colours every census dissemination block in Canada by how long it takes to walk to things. That choice of shape — the block — was inherited, not chosen: it’s the geography the census hands you, and it’s what our travel times attach to. This spring we asked whether it’s the right shape, by routing a hexagonal grid over Hamilton and comparing.
The short answer: blocks are already fine in cities, and badly wrong in rural villages.
The experiment
We laid 71,242 H3 resolution-10 hexagons over the Hamilton census subdivision and routed every one of them the same way the production map routes blocks — real road network, slope-aware walking speed, 60-minute cap, all 18 amenity types. Same colours, same ceiling, same sentinels, rendered in the real app, so any visible difference is geometry and nothing else.
Cities: blocks are already fine
Hamilton’s median block is 0.022 km² — about 149 m across, which is finer than a res-10 hex (132 m across). Downtown, hexes add nothing: the blocks are already smaller than the grid you’d replace them with.
Villages: the block lies
Rural blocks are enormous, and one number has to stand for everyone inside. The village of Lynden sits in a 5.45 km² block with 347 people. The block says the grocery store is a 30-minute walk. The 327 hexes inside that block say 30 to 60 minutes, with a median of 51:
The block understates the median resident’s walk by 21 minutes — not because the routing is wrong, but because one origin point has to speak for an area forty times the size of a downtown block.
| Where | Median block | vs a 132 m hex |
|---|---|---|
| Downtown Hamilton | ~149 m across | already finer |
| Lynden (rural) | 5.45 km² | ~313 hexes per block |
The number you’d publish if you didn’t check
One methodological trap worth recording: the shipped Hamilton surface caps walk times at 30 minutes. If you compare hexes against blocks without dropping the capped values, you get a mean error of −11 minutes and 66% of blocks “off” by more than 5 — dramatic, and fake, because the censored values manufacture disagreement. Drop them and the real figures are −2.7 minutes and 23%. The dramatic number is the one you’d publish if you didn’t check.
What this means for the map
The value of hexes is concentrated where blocks are big — which is exactly where Canada’s map is emptiest and least trustworthy today. The plan that came out of this spike is hybrid: keep blocks where they’re already finer than the grid, subdivide only the blocks that are too big. That work is now a real pipeline — plan, route, tile, verify — and it gets its own note when it ships.