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Merge pull request #3897 from mapycz/refactor-scale-denom

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Scale denominator: a bit of refactoring
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Artem Pavlenko 2018-05-09 08:46:09 +01:00 • committed by GitHub
commit b7e486d3c3
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1 changed files with 7 additions and 2 deletions
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9
src/scale_denominator.cpp
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@ -23,17 +23,22 @@
// mapnik
#include <mapnik/scale_denominator.hpp>
#include <mapnik/global.hpp>
#include <mapnik/well_known_srs.hpp>
// stl
#include <cmath>
namespace mapnik {
static const double meters_per_degree = 6378137 * 2 * M_PI / 360;
static const double meters_per_degree = EARTH_CIRCUMFERENCE / 360;
double scale_denominator(double map_scale, bool geographic)
{
double denom = map_scale / 0.00028;
// Pixel size in meters.
// Corresponding approximate resolution is 90.71 DPI.
constexpr double pixel_size = 0.00028;
double denom = map_scale / pixel_size;
if (geographic) denom *= meters_per_degree;
return denom;
}