PlateReaderMap counts validated source records as documented ALPR locations. That is narrower than claiming a physical inventory: one mapped record may not reveal the number of lenses, lanes, or devices at a site, and an unmapped device cannot appear in the count.

The unit of count

Each accepted OpenStreetMap object receives a stable source identifier. A point normally represents one documented location. If a relevant source object is a line or area, the data pipeline converts it to a consistent representative point and retains its original object identity.

Records with invalid coordinates are excluded. Potential duplicates are handled conservatively so that nearby but distinct installations are not automatically merged. The source’s ALPR tagging guidance remains the basis for identifying relevant OSM records.

Manufacturers and unknown values

Manufacturer totals come from documented source tags. Obvious naming variants can be grouped under one display name, but the original value is retained for review. Missing manufacturer data stays in an “unknown” or “not documented” category; camera appearance or nearby deployments are not used to guess a vendor.

Percentages must state their denominator. A manufacturer’s share of records with a known manufacturer is different from its share of all documented locations.

Geographic totals

Coordinates are assigned to states, counties, and qualifying places with an offline spatial join. The Census Bureau’s TIGER/Line files contain geographic boundaries and entity codes used for this kind of assignment. Boundary vintage and source quality can affect the jurisdiction attached to a point near an edge.

National totals are reconciled with the sum of their underlying records before publication. Population or area-based rates appear only when compatible source data is available and the comparison is meaningful.

Current counts and historical change

PlateReaderMap compares each validated snapshot with the previous accepted snapshot. A new source object is described as newly documented. A disappearing object is described as no longer present in the source dataset unless another reliable source confirms a physical removal.

Historical tracking begins with PlateReaderMap’s first successfully preserved snapshot. Earlier trends are not reconstructed without a reliable historical source, and trend sections remain limited until enough observations exist.

Sources and further reading