screenPPIbyOGC top-level constant

double const screenPPIbyOGC

OGC defines a screen pixel of 0.28 mm that approximates to 90.7 ppi.

OGC specifies: pixelResolution = 0.00028 * scaleDenominator that gives scaleDenominator = pixelResolution / 0.00028.

Another way to calculate a scale denominator: scaleDenominator = pixelResolution * screenPPI / 0.0254

This constant: screenPPIbyOGC = 0.0254 / 0.00028

Abbreviations:

  • PPI = pixels per inch
  • OGC = The Open Geospatial Consortium

Implementation

const screenPPIbyOGC = 0.0254 / 0.00028;