Three things about this surface are choices rather than measurements. Each one is exposed
as a control or a number rather than baked in quietly, because each one can change what the
map appears to say.
Choice 01
Smoothing is an argument
The page opens at 5 km on a 20 km grid — a quarter of a cell, which is to say
almost nothing: a bar of 245 means 245 buildings standing in that square. Widening the
bandwidth spreads each facility across its neighbours, and the smooth mountains that
result are partly the kernel, not the country.
So the slider stays
The bandwidth is a control on the page rather than a constant in the build, so any
shape you find can be checked against the raw bins.
Choice 02
A market is a judgement
Markets here are single-linkage clusters: facilities within 22 km of another
member, eight members minimum. That chains — Northern Virginia runs 116 km from the
District through Loudoun County, because the build-out genuinely does.
Found by data, named by hand
The clustering names each group after its most common member city; the familiar market
name is a lookup applied on top. Both are shown in the table below.
Choice 03
Equal area, at a cost
Height is comparable across the map only because the projection is equal-area, which
rules out the usual albersUsa insets: they draw Alaska at about a third of
true scale, so an Alaskan bar would be inflated ninefold.
Excluded, not forgotten
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