Function msInchesPerUnit

mapscale.c:113–146

}

double msInchesPerUnit(int units, double center_lat)
{
  double lat_adj = 1.0, ipu = 1.0;

  switch (units) {
  case(MS_METERS):    
  case(MS_KILOMETERS):
  case(MS_MILES):
  case(MS_NAUTICALMILES):
  case(MS_INCHES):  
  case(MS_FEET):
    ipu = inchesPerUnit[units]; 
    break;
  case(MS_DD):
    /* With geographical (DD) coordinates, we adjust the inchesPerUnit
     * based on the latitude of the center of the view. For this we assume
     * we have a perfect sphere and just use cos(lat) in our calculation.
     */
#ifdef ENABLE_VARIABLE_INCHES_PER_DEGREE
    if (center_lat != 0.0)
    {
        double cos_lat;
        cos_lat = cos(MS_PI*center_lat/180.0);
        lat_adj = sqrt(1+cos_lat*cos_lat)/sqrt(2.0);
    }
#endif
    ipu = inchesPerUnit[units]*lat_adj;
    break;
  default:
    break;
  }

  return ipu;
}


#define X_STEP_SIZE 5