engleski

The identification and calibration of the airborne multisensor acquisition system

An airborne multisensor system was developed and realized in the frame of the project, its primary aim is to provide the airborne civil service of the reconnaissance and the surveillance in the crises' situations and the protection of environment. This is a multipurpose airborne remote sensing system. Besides its primary role it will serve as the laboratory for the research in different scientific disciplines too. The paper considers requirements, approaches and experience of the identification and the calibration of the system. There are two reasons that require the identification and the calibration of the system: first, to use full potential of applied sensors ; second, to provide set of the operational parameters that enable variety of the applications. The goal of the first case is to assess the relevant reference characteristics of used sensors in the ideal conditions (single sensor, no processing, no movement, a well defined scene, no transmission and the compression of the imagery). The available technical data for used sensors are not complete, only basic information is available, and the calibration and identification serve to provide the reference (ideal) characteristics of sensor. When implemented in the system, the characteristics of the particular sensors will be degraded ; the measure of the degradation will serve as a criterion for the evaluation of the design of the system. For the secon case (different applications of the system), it is necessary to identify and to calibrate the basic operational characteristics of the whole system and not only of the isolated sensor in the ideal conditions. When the basic operational characteristics of the airborne multisensor system were determined the estimation of their behavior is possible for changeable conditions. The considered airborne multisensor acquisition systwm form the following subsystems: a) passive digital electro optical sensor, b) acquisition hardware, c) acquisition software, d) synchronization subsystem, e) positioning and orientation subsystem, f) control of imaging angles for two sensors, g) radio transmission of the selected imagery from the aerial platform to the ground, h) subsystem for the navigation, i) moving map, j) subsystem for the automatic tracking of the aerial platform by GPS-GSM. The most important feature of the considered systemis its ability to parametrically geocode images oving to data collected by inertial measuring unit and GPS and the use of the software for the parametric geocoding (PARGE). In the system are applied following sensors: 1) hyperspectral line scaner V9 that can work in sampling or in the imaging mode ; 2) multispectral camera MS-3100 ; 3) longwave infrared (thermal) camera Photon, 4) color video camera Sony FCB-IX11AP ; 5) digital photo color camera Fuji FinePix S2. A hyperspectral scanner V9 covers up to forty-five channels and the multispectral camera MS-3100 covers four channels in the visible and near infrared wavelengths.Thermovision camera Photon works in the long-wave infrared range from 7.5 to 13.5 micrometers. Other two sensors cover red, gren and blue channels in the visible wavelengths. Calibration includes measurement of the modulation transfer function (MTF), ground resolving distance (GRD), radiometric response for used channels (except for V9), and spatial acuraccy. For the radiometric calibration is used target Spectralon SRT-MS-180 (LabSphere), for hyperspectral sensor is provided ground truth measurement by means of the FieldSpec 3 Spectroradiometer (ASD), for Photon are used data of the temperature collected by data loggers. Extensive calibration and identification was performed and the airborne multisensor system is now provided by a rich set of the characterustics.

multisensor; multipurpose; calibration; radiometric calibration; modulatio transfer function

nije evidentirano