reading the signal…
Signals / Object / Street-level imagery
in San Francisco, CA·counted·21 all time
Shellstone is a natural building stone containing visible shell fragments, typically used for walls, facades, or landscaping.
Counted, not streamed: Shellstone has no time series, so it is read as a footprint across places. All-time count by city.
Things that physically exist: street furniture, signs, buildings. All-time counts.