EXPERIENCE WITH.HYBRID INFRARED-VISIBLE VIEWING 
FROM LOW FLYING AIRCRAFT 
Richard RTice, AGA Infrared Systems AB, Lidingô, Sweden 
Rolf A Larsson, VIAK AB, Falun, Sweden 
ABSTRACT 
The paper begins with a review of experience with live 
thermal infrared imagery experience in light airplanes 
as background to subsequent development of a sidelooking 
hybrid infrared-on-visible viewing system for helicopters. 
The resulting portable airborne instrument assembly is 
described briefly. 
Techniques for registering the hybrid view on standard 
35 mm colour film and 1/2-inch video tape cassettes, 
while using the system simultaneously for detecting 
thermal anomalies in the overflown terrain, are described; 
in addition to filming through the viewing eyepiece to 
produce 16 mm sequences presented at the conference in 
Freiburg (from which figures for this paper were taken). 
Helicopter trials using microwave telemetry in the 
2.5 GHz band, for monitoring the airborne operator's 
hybrid view in realtime on the gorund, are reported; 
as well as night-flight trials with the operator wearing 
passive night vision goggles to restore the visible 
terrain features lost in the hybrid view due to darkness 
in the visible (but not the thermal infrared) wavelengths. 
The paper concludes with a discussion of various appli- 
cations for live hybrid infrared-visible viewing from low 
altitudes in support of established remote sensing methods, 
including current flight-trial status, in the fields of: 
area firefighting support, building thermal performance, 
inland waterway surface temperature mixing, earth dam 
and dike condition, area drainage project performance, 
powerline network condition, microclimate investigation, 
geothermal source survey, big game censusing and plant 
stress detection in forests. 
INTRODUCTION 
During the past decade, both interest in and the need for 
thermal infrared technology have grown rapidly, for natural 
resource inventories, environmental control, urban planning, 
etc. The demand for information from small as well as large 
scale thermal registration, analysis, and presentation is 
increasing as fast as any new IR system capabilities are 
developed.