Thermal Cameras vs Thermal Grids — Which Wins on a Cargo Deck?
Both can image temperature. They fail in different places. On a cargo deck the failure modes are what determine the answer.
Almost every conversation we have with a new operator includes the question: "Why not just install a few thermal cameras?" It is the right question to ask. Here is the comparison we walk through.
What a thermal camera does well
A modern microbolometer-array thermal imager gives you 320×240 to 640×480 pixels of temperature at high frame rates over a wide angular field. From a single mounting point it can resolve temperature differences of less than a degree across an entire visible scene. For overlooking an open yard or a clear corridor, it is excellent.
What it does badly on a vehicle deck
Line of sight is occluded
Vehicles park bumper-to-bumper, three deep, with internal columns and overhead bracing in between. A camera mounted at one end of a deck sees the back of the first row of vehicles and almost nothing else. Adding cameras to cover the gaps multiplies cost without solving the underlying geometry.
Underbody is invisible
EV battery packs are in the underbody. A ceiling- or wall-mounted camera looks at the roof of the vehicle, which is the surface least thermally connected to the pack. By the time the pack temperature reaches the roof, the event is well advanced.
A single fault is a coverage outage
A camera failure or lens occlusion takes its entire field of view offline. With a small number of cameras, that is a meaningful percentage of the deck.
What a thermal grid does well
A thermal grid distributes many small IR sensor cells across the overhead at vehicle-pitch density. Each cell has a narrow field of view scoped to one or two vehicles. Coverage is per-vehicle and survives partial damage — losing one cell loses one vehicle of coverage, not a deck.
Where it is weaker
Each cell is a low-pixel sensor. You lose the imaging resolution of a camera. For surveillance or scene interpretation this matters; for per-vehicle anomaly detection it does not — the question being asked is "is this cell anomalous against its baseline" rather than "what does the scene look like."
The comparison at a glance
Cost shapes the choice
Cameras are individually expensive but few. Grids are individually cheap but many. At the deck-coverage level the installed costs are within a small multiple of each other — but the coverage characteristics are not equivalent. A grid covers what a camera cannot, and degrades gracefully where a camera fails open.
Where each belongs
- Open weather decks and yards: camera is often a good fit (clear line of sight).
- Enclosed vehicle decks: grid is the right primary; cameras are useful as a secondary on access lanes.
- Engine rooms: neither — that is a different problem with its own established detection layer.
Sources
- IMO — SOLAS Chapter II-2 / FSS Code Chapter 9, fixed fire detection requirements for vehicle and ro-ro spaces.
- IMO MSC.1/Circ.1638 — fire safety guidance for ro-ro spaces carrying vehicles.
- DNV — guidance on fire-detection coverage and camera-based detection on car carriers.
- [VERIFY: per-vehicle vs per-deck coverage and failure-scope comparisons are RoRoSafe engineering analysis, not third-party benchmarks.]
Continue the thread
What Causes EV Fires in RoRo Ships?
The headline answer is "lithium-ion batteries." The operational answer is more useful — five compounding factors that turn an unremarkable fault into a casualty.
How Are Thermal Hotspots Detected on Cargo Decks?
The detection problem on a cargo deck is not measurement — IR sensors are commodity. It is deciding which delta in which cell at which time is real.
Can Gas Sensors Detect Lithium-Ion Runaway?
Yes — and earlier than thermal in some environments. The harder questions are which gases, where to mount the sensor, and why we treat it as a complementary layer at sea.