From One Camera to a Site’s Terabytes

Ada re-derives this chapter’s own numbers step by step, at full precision

ADA · CALCULATION AUDIT

From One Camera to a Site's Terabytes

The chapter puts one 4 Mbit/s camera at about 43 GB/day and a 50-camera site at roughly 2.1 TB/day — the numbers that decide whether the cloud path is even possible. An edge that emits one 200-byte event per second instead sends about 2,500x less. This audit carries the figures in full, from one camera to a site’s terabytes.

Companion to the chapter Edge-Fog Use Cases — every number here comes from that chapter.

Ada: This chapter claims one 4 Mbit/s camera is about 43 GB/day and a 50-camera site is roughly 2.1 TB/day. Those are the numbers that decide whether the cloud path is even possible, so let me carry them in full.

• One camera. 4 Mbit/s x 86,400 s/day = 345,600 Mbit/day. Converting bits to bytes: 345,600 / 8 = 43,200 MB/day = 43.2 GB/day.
• Fifty cameras. 43,200 MB x 50 = 2,160,000 MB/day = 2,160 GB/day = 2.16 TB/day — the “2.1 TB” the chapter quotes.
• The event alternative (illustrative). If the edge instead emits one compact 200-byte event per second, that is 200 x 86,400 = 17,280,000 bytes/day = 17.28 MB/day per camera — about 43,200 / 17.28 = 2,500x less than the raw stream.

That 2,500x ratio is the whole argument for edge extraction: sending occupancy counts and shelf-gap events instead of pixels turns a site’s terabytes into megabytes while keeping the operational answer. The ratio only holds if the missed-event risk is measured against the retained sample, not assumed away.

Every number above is taken from the chapter’s own material and re-derived step by step.