Spatial Resolution of the Remote Sensing System when Changing the Angle of Sighting

Abstract

Background. The Earth remote sensing systems are widely used to monitor the Earth's surface (ES) by aviation and space vehicles equipped with thermal infrared systems (TIRS) for surveillance. The obtained data are used for solving environmental and nature-resource problems, development of fundamental research in the interest of the country security and defense. The effectiveness of the TIRS on aircraft is characterized by the resolution of the terrain which is determined by the spatial resolution of the system.

Objective. The aim of the paper is the development of TIRS physico-mathematical model for calculation of projections of all pixels of the focal plane array (FPA) on the ES at different angles of sighting.

Methods. On the basis of the analysis of the physico-mathematical model, it is proposed to calculate the deformed projection of all pixels of the FPA on the ES using the theory of angular motion.

Results. Practical results give an idea of how much the spatial resolution of the projection of reference pixels at the angles of sighting (cases № 1–3) differs from the projections when the FPA is located in nadir (case № 0). There are three cases according to the considered example:

–   when only the pitch is deviated by 35º, the spatial resolution increases from 1.22 to 1.57 times (case № 1);

–   when only the roll is deviated by 35º, the spatial resolution increases from 1.01 to 2.44 times (case № 2);

–   when both pitch and roll are deviated by 35º, the spatial resolution increases from 1.17 to 3.24 times (case № 3).

The results of the design show that at a deviation in the angles of sighting, the size and shape of the projections of the pixels of the FPA increase and deform more when they move away from the nadir. It is also important that the projections of rows and columns of the FPA deviate to different angles which significantly affects the image quality, formed by the linear CCD array.

Conclusions.The analysis of the proposed physico-mathematical model showed that the height doesn’t affect the shape of the deformation of the projection of pixels, but is only a scaling coefficient in the transition from angular to linear coordinates. At the same time, among other parameters that affect the shape of the projections of pixels, the sequence of deviation in the angles of sighting “pitch–roll” and “roll–pitch” also get its effect.