Why do low flying aircraft chart areas at night?

Question

Last night in the middle of the night, I kept hearing a low flying aircraft fly overhead (2000ft). I'm out in the country-side so the noise was very noticeable in the quiet night. When I checked flightradar24, the aircraft appeared to be moving back and forth in a grid pattern across several small cities in the state and even over a chunk of the country-side. When I see this during the day, I just assume they are taking pictures for map making. Why would they be doing this at night?

score 9 · Answer 1 · answered Mar 29 '24 at 15:05

9

That’s definitely a survey pattern, in addition to photography surveying can use LIDAR to make very accurate maps.

answered Mar 29 '24 at 15:05

300D7309EF17

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Someone else suggested that to me as well. He also said it was unusual to do at night since you can't capture the visual light spectrum. The tail number wasn't available either, idk how common that is though. – rtaft Mar 29 '24 at 15:37
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@rtaft in the future you can check adsbexchange, it shows a lot more “blocked” tail numbers than commercial sites. But it’s clearly a survey pattern. – 300D7309EF17 Mar 29 '24 at 15:51
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Winds are often calmer at night, which would improve accuracy. LIDAR doesn't need to be aligned to simultaneously recorded visible light images, because GPS is enough. So you might as well do that at night, when the airplane's otherwise idle. – Camille Goudeseune Mar 29 '24 at 20:21
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@CamilleGoudeseune - and likely easier to fly whatever path you want, or at least not be quite as concerned with other traffic. – Steve Pemberton Mar 29 '24 at 20:58

mins · Accepted Answer · 2024-04-01T18:12:53.367

In short

Tracks, distant of about 300m, covering only cities, Oswego, Fulton, Pulaski and Watertown. It's indeed difficult to be sure, but my guess is the aircraft is conducting thermography, measuring the temperature of the ground to detect fluid network leaks or evaluate buildings insulation.

Local administrations are conducting nowadays thermal surveys to locate poorly insulated buildings. An example of business performing such activity.

Edit: You found the aircraft and the company behind this project, confirming this possibility:

PA-31 registered C-FVZM, owned by Aries Aviation, a company working in remote sensing, and thermography.

Source.
Aries's final customer is MyHeat, a Canadian company providing heat loss maps for housings to customers, with great details.

A paper on this application: Geospatial Technologies to Improve Urban Energy Efficiency

More details

In daytime the Sun light heats the Earth with rays going visible to infrared wavelengths. At any time Earth surface and objects slowly reradiate this heat to the atmosphere, but only in the form of infrared radiation (IR), according to the black body radiation model for temperatures centered on 15°C. IR represent a much larger spectrum than visible light:

Source.

These IR radiations are the ones trapped by GHGs. Human eyes cannot perceived IR, and night appears black to us, but appropriate sensors can see IR, for them night is not dark at all.

To measure energy radiated by Earth surface and objects, it is preferable to work when they don't reflect Sun's light, night is ideal.

Leaks on a city steam network:

Source.

Inventory of heat losses in a city:

Source.

And the same from the company paying for the thermal mapping of your area:

Source.

See The Benefits of Aerial Infrared Thermal Mapping

Why do low flying aircraft chart areas at night?

2 Answers2