Eight systems. Six ways to think.
Only one of these systems is a counting problem. The rest are assembled, aggregated, distributed, measured or derived — and a platform that treats all eight as symbol-spotting will be wrong on seven of them.
Pick a system below and work through it. The drawing changes, and so does what you have to do to it.
- CCTV-001: External WP camera — grid A/1
- CCTV-002: External WP camera — grid B/1
- CCTV-003: External WP camera — grid C/1
- CCTV-004: External WP camera — grid D/1
- CCTV-011: Internal dome camera — grid A/1
- CCTV-012: Internal dome camera — grid B/1
- CCTV-013: Internal dome camera — grid C/1
- CCTV-021: Corridor camera — grid A/2
- CCTV-022: Corridor camera — grid C/2
- CCTV-031: Internal dome camera — grid A/3
- CCTV-032: Internal dome camera — grid B/3
- CCTV-033: Internal dome camera — grid B/3
- CCTV-041: Lift car camera — grid C/3
- CCTV-042: Lift car camera — grid C/3
- CCTV-051: Pole-mounted camera — grid D/3
01 / 04The sheet as issued.
The system isn’t the category. The reasoning is.
Systems group by discipline on a drawing register, but they group by reasoning in a takeoff. Two systems that look nothing alike can need identical thinking, and two that sit on the same sheet can need completely different thinking.
- 01COUNT
- The tally is the answer — but only once you know what a label means.
- 02ASSEMBLE
- One symbol implies a set of devices that were never drawn.
- 03AGGREGATE
- Points roll upward into the infrastructure they force to exist.
- 04DISTRIBUTE
- Topology and coverage decide the quantity, not the symbol count.
- 05MEASURE
- The number is a dimension. Counting it correctly still gets it wrong.
- 06DERIVE
- The quantity comes from another discipline's drawing entirely.
ELV takeoff is an engineering problem, not object detection.
Object detection answers “what symbols are on this sheet”. That is a real question, and it is the first ten per cent of the job. The remaining ninety is knowing that a TYP. note multiplies, that a door implies five devices, that outlets force patch panels into existence, that a boom must out-measure its lane, and that the disabled toilet alarm quantity was never on your drawing in the first place.
That knowledge is engineering. It is what the platform models, and it is why the engineer stays in the loop rather than being replaced by a detector.