The experience presented in this paper is based upon work 
with the portable AGA Thermovision thermal-IR camera 
equipment in various guises, while flying at low altitudes 
in light-to-medium fixed-wing and rotory-wing aircraft 
during the past few years. 
PRELIMINARY FLIGHT TRIALS IN A LIGHT AIRPLANE 
The thermal registrations were made with the AGA Thermo- 
vision 750 camera unit (which has a single liquid nitrogen 
cooled InSb detector element, in the 5 um band) suspended 
within a specially built "photo door", replacing the 
standard door of the airplane: a Cessna 185 (Larsson, 1976). 
The registrations were made to monitor the local micro- 
climate and heat leakage from buildings in dwelling areas 
of Uppsala, Sweden. The work was performed at night in 
June, at flying heights between 300-1000 m, looking 
straight down with the help of a frontsurface mirror 
into which the front lens of the horizontally aligned 
IR camera was directed. 
  
The experience from these tests can be summed up as 
follows: 
- It is a practical, technical possibility to register 
thermal radiation from the ground and to document its 
distribution pattern with the AGA Thermovision 750 
mounted in a light airplane. This standard equipment 
is easy to handle and requires modest installations 
in the plane.Through the use of light airplanes the 
operational costs are low. 
- The visual, realtime presentation during the flight 
gives a very good possibility for detection, thorough 
inspection and documentation of IR radiation anomalies 
in the area surveyed. 
- The detection can be influenced by reflected sunlight 
from an object, and not just by the emitted IR radiation. 
Registration flights shall thus be performed during 
dusk or at night, or alternatively, with an "anti-solar" 
filter in the camera. 
- The isotherm function of the Thermovision 750 can rarely 
be used to an optimum while registration is done from 
an airplane, since the objects of interest disappear 
so rapidly from the field of view of the downward- 
looking camera lens. 
- Thermal information is lost from the thermal display image 
signals by photographing the screen with a Polaroid- 
camera or other photorecording means. 
With this experience from the preliminary trials as a back- 
ground, some lines of direction for practical operational 
flight thermographic activity could be stated: