Space imagery has tilt angles affecting the shape and size of the pixel projection on the terrain. The author proposes the formula for determining the size of the sides of the pixel projection on the ground depending on the camera tilt angles (pitch and roll). It is shown that the camera tilt angles influence the rectangular shape of a pixel projection on the ground. The author proposes to replace the rectangular projection of a pixel on the ground with a square of equal area. The formula for calculating the value of the size of the equivalent square is proposed. The size of the equivalent square will characterize the spatial resolution of the inclined satellite image.