Impact of point spread function of MSG-SEVIRI on active fire detection

Abstract

The spatial resolution of sensors is a concept frequently described in an inappropriate way, usually identified by the sampling distance in the image capturing process. The shape of the modulation transfer function (MTF) has no influence on the results in applications based on homogeneous distribution of radiance. However, in the case of high-temperature events (HTEs), the spatial location of the burning area inside the pixel is a key issue to solve, in order to quantify the radiance. The point spread function (PSF) should be considered both in fire detection-oriented algorithms and in the application of bispectral processes. This paper analyses the impact of the PSF of the Meteosat Second Generation Spinning Enhanced Visible and Infrared Imager (MSG-SEVIRI) sensor on the determination of thermal fire parameters. The PSF influence on the brightness temperature (BT), in the mid-infrared (MIR) 3.9 μm spectral band, on detection algorithms is analysed. Errors in the fire temperature retrieved by the bispectral technique, due to non-coincidence in the PSF involved, are also analysed. The results obtained show a difference of around 20 K in the BT in the 3.9 μm spectral band, depending on the fire location inside the pixel. Finally, the probability detection of the minimal size of the burning area was analysed, and revealed that there is a 90% probability of detecting a fire with a burning area of 10 ha whereas an area of 4 ha is detected with a probability of 50%.