Cannabis Farm Detection using Thermal Imaging

Thermal imaging has been used for detecting cannabis farms in buildings by seeing unusually hot walls/roofs of buildings for many years very effectively. This has mostly been via helicopters, and more recently UAVs and handheld (with screen) thermals, which are all quite expensive. A much more affordable solution is a handheld monocular thermal called the FLIR SCION.

The problem:

For spotting of cannabis farms, helicopter thermals are very expensive, as is deployment of a helicopter. UAVs require a specialist operator and restrictions on where they can be flown and are also relatively expensive. Handheld thermals with screens (thermography cameras) still cost at least £2300 +VAT for one with 320×256 resolution (needs to be 320×256 or higher).


FLIR SCION monocular thermals have “lock span” feature, allowing officers to compare buildings and detect cannabis farm heat. Most monocular thermals don’t have this feature.

There are then 3 advantages to using a thermal monocular over a handheld (screen) thermal camera:

  1. More affordable. They price from £1800 up to £2500 (+VAT), depending on model.
  2. The lenses are designed for longer ranges, making them more useful to police (5m to 1100m)
  3. As a monocular, it is simpler to use, more user friendly and rugged for other police uses such as:
    – Searches for suspects (urban or rural) 5m up to 1100m range for a person
    – Covert surveillance (no screen lighting you up at night)
    – SFO/ARV/CTSFO armed police team surveillance and spotting
    – Perimeter security (festivals/events, key infrastructure such as Nuclear Power Stations and transport of dangerous materials)
    – Rural police operations (copes with field/woods distances and farmyard searches, whilst staying covert)
    – Transport police for rail line searches (suicide prevention and recovery, metal theft, trespassing)
    – SAR


FLIR SCION come in different lens and resolutions, depending on distance you need to see and sharpness of image. For detection of cannabis farms in buildings, the range is typically less than 100m, so OTM266, PTM166 will achieve results with their 14-18mm lenses and 640×512 resolution. They will also detect a person out to 400m (look like a “blob” of heat at that range), or recognise it is a person (not a deer/cow) at roughly 193m or less.

OTM366 or PTM366
Detect: <710m
Recognise: <350m

Detect: <1.1km
Recognise: <450m

Other useful features:

  • Image and video save for evidence collection
  • Wifi streaming to phone/tablet or via 4G/5G hotspot to VMS/HQ for live sharing
  • IP67 waterproof and 2m drop tested (rugged) with 3yr warranty (10yr on the sensor)
  • Built-in compass. GPS for all models.
  • Rechargeable battery option for 8-10hr operation life. Extend with most powerbanks in the field if needed
  • Manual focus for OTM366, PTM366 and PTM466 models = sharper image focus