remote sensing

Remote Sensing with a Thermal Imager on an Environmental Helicopter - First Experimental Results; 10-1994

presented at
Twentieth European Rotorcraft Forum
Oct 4-7, 1994, Amsterdam, The Netherlands

In 1992 several test flights with a color coded thermal imaging camera on a BK 117 were made at Eurocopter Germany.

The task was to get first experience of apparent IR-signature of a landscape in top-view from a helicopter. The measurements were made on a research farm with the intention to find a relation between surface temperature and soil moisture. During measurements on a waste deposit a hot spot was found. At present experiments are performed with an additional scanner in the 3-5 µm range mounted parallel to the line of sight (LOS) as the inital scanner with a 8-12 µm detector. Actually an environmental helicopter is in development, which will be equipped with several sensors including a spectroradiometer for the visible and near IR wavelength-bands.

1. Introduction Airborne HC remote sensing systems have proved to be very useful for monitoring agriculture and coastal regions, for rapid assessment in response to environmental pollution and disasters and for demonstration of new sensor concepts; see chapter
2. A BK117 was equipped with a real-time, color-coded thermal imaging camera from AGEMA which was used in an experimental trial to monitor AGRO-ECOsystem FAM (Forschungsverbund Agrarökosysteme München) and a waste deposit. The Thermovision 900 camera is a temperature measurement system with a spectral response in the ranges of 3-5 µm and 8-12 µm. The resolution is 12-bit for high image quality to get IR-signature from a.m. agro-ECO applications. The measured data were digitally stored for each image and live scenes were recorded on video tape. During summer 1992 EUROCOPTER Deutschland (ECD) has made several flight campaigus. One campaign was extended with three flights during a day to learn about the temperature/radiance changes; see chapter
3 and 4. At the research farm (143 ha) "Klostergut Scheyern" (FAM project) in the tertiary hills of Munich, three types of cultivation were situated - conventional agriculture, sustainable agriculture and landscape conservation. These types were monitored for their influence on the ecological and economical cycles in the ecosystems especially on ground. With the remote sensing of rural surfaces it is possible to measure surface temperatures not only of single points on ground (grid of 50m x 50m). These surface temperatures depend mainly on the content of moisture of the soil. Effects of solar radiation, wind, plant parameters incl. spectral emissivity/reflectivity and the angle of detection have to be taken into account during the evaluation/interpretation. The paper represents results of the spectral radiance of different materials, the daily course of radiance and the relation between surface temperature and soil moisture. Addional measurements on a waste deposit showed strong chemical activity for some parts of the disposal which could not be seen in the visible spectrum; see chapter
5. At present there are ongoing experiments with an additional scanner (3-5 µm) mounted in the same line of sight as the first camera head (8-12 µm). In an ground measuring campaign different kind of trees were analysed; see chapter 6. The trials will be extended in the future with an helicopter-mounted spectroradiometer (visible and near IR Range) to detect the red-edge effect of chlorophyll. With this remote sensing techniques the crop type, the surface roughness, the growth of vegitation (biomass), evapotranspiration, vitality of plants, vegetation stress etc. can be monitored by thermal imaging systems mounted in helicopters; see chapter 7.