What Australian car park data actually contains

“How many spaces are free” has a different answer in every city. Building Car park availability meant finding out what each source really publishes.

Source	What it gives
Adelaide UPark	live free spaces for 10 car parks; no capacity and no location
Transport for NSW	live occupancy; needs an API key
Brisbane	a forecast of occupancy, for 617 metered zones
Wilson Parking	locations and services for 568 car parks
Sydney, Perth, ACT, Hobart	locations; Perth also gives capacity

Things that follow from that:

• Brisbane’s numbers are predictions. The council publishes a forecast per zone and hour. They are worth showing, and have to be labelled as estimates.
• Adelaide’s live data has no coordinates. The reports name a car park and a number. The locations had to be taken from OpenStreetMap.
• A free count without a capacity cannot be a percentage. Adelaide’s spaces add to the total free figure for an area and are left out of the occupancy percentage.
• The ACT’s car parks are polygons. A point for each has to be computed as the area-weighted centroid.
• Brisbane’s portal returns at most 100 records per request, so anything larger has to be paged.
• Wilson’s endpoint ignores the search centre once the radius is large enough, so a single request returns the national network.

Tracking every car park in the country comes to roughly 1,900 entities, so the integration defaults to a radius around home.