Side looking airborne radar

Cone- and azimuth angle are related by cosα = cosφ ∙ cosε.

On the earth surface the wave comes in at the (nominal ellipsoidal) incident angle β with respect to the vertical axis at this point.

The direction of the incoming wave relative to the horizontal plane may be measured also.

The angle θ = ε + 90° is used for a mathematical description in a spherical coordinate system.

(in the figures shown as a red arrow) pointing from the antenna to a ground scatterer.

The variable u is u = cosα with α as the azimuth angle between the line of sight and the x-axis (direction of flight).

The range resolution (the ability to separate the pixels of the image perpendicular to the direction of flight) of a SLAR depends on the length of the transmitted pulse.

At the ground of Earth the range resolution has an inverse relationship with the depression angle: The pulse width

and the highest the range resolution, but the lower the echo signal.

It is derived from the ratio of the physical size of the antenna (the real aperture) to the wavelength used.

It is apparent that SLAR antennas as real aperture could not be built large enough to achieve the desired azimuth resolution.