Graphic coordinates

The unit of the graphic coordinates is one Picture Element, a Pixel. A Pixel is the smallest element displayed on a bitmap. The real physical dimension of the pixel depends on the resolution of the scanner used. If you scan the map source using a scanner with 400 dpi resolution (400 dots per inch), one pixel represents an area of approx. 0.064 mm in size.

The accuracy of the final digitalized coordinates is therefore significantly influenced by the resolution used. The volume of the raster data also depends on the resolution (doubling the resolution enlarges the bitmap four times). Therefore, it is necessary to find a compromise between the required accuracy and acceptable size of the bitmap.