1.1.3. Minimum Dimensions

The picture on the left shows how lines with different line thicknesses are visualised on a screen. You might be surprised not to see the expected difference of the width of two lines. For example with the Adobe SVG Viewers 3.0 and 6.0, line widths do not increase linearly, but grow irregularly. Lines between 0 and 0.3 pixels are always rendered with the same width and in gray colour. Between the pairs 0.3/0.4 pixel and 0.6/0.7 pixel differences of the apparent line width become recognizable. Other renderers may have completely different characteristics. (Räber et al. 2003)

A series of test objects is used to identify the minimum distance between two surfaces. In order to unequivocally differentiate the two areas, they have to be separated by at least 1 pixel. A similar test can be done with lines to find the minimum distance for linear elements. As you can see in the right figure 1.5 pixel is that minimum distance. But for very thin lines the distance is 2 pixels, since they are rendered in grey. (Räber et al. 2003)
Recommended distances: between two surfaces: 1 Pixel; between two lines: 1.5 Pixel (for very thin lines: 2 pixels)

Equally, the minimum areal dimensions of point signatures at which signatures can be identified unambiguously, can be examined. It is between 4 and 5 pixels. (Räber et al. 2003)
Recommended aerial dimension of point signatures: 4-5 Pixel