dodecaphonic · January 21, 2015 18:32 · Jan 21, 2015
diff --git a/compare_projections.rb b/compare_projections.rb
@@ -0,0 +1,35 @@
+require "rgeo"
+
+WGS84     = "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs"
+WGS84_UTM = "+proj=utm +zone=22 +south +ellps=WGS84 +datum=WGS84 +units=m +no_defs"
+
+x0, y0 = -48.10311146131618, -15.894902327065926
+x1, y1 = -48.103022948419394, -15.894858472899413
+
+mercator   = RGeo::Geographic.simple_mercator_factory
+geographic = RGeo::Geographic.projected_factory(projection_proj4: WGS84)
+spherical  = RGeo::Geographic.spherical_factory
+utm        = RGeo::Geographic.projected_factory(projection_proj4: WGS84_UTM)
+
+p0m = mercator.point(x0, y0)
+p1m = mercator.point(x1, y1)
+
+p0g = geographic.point(x0, y0)
+p1g = geographic.point(x1, y1)
+
+p0s = spherical.point(x0, y0)
+p1s = spherical.point(x1, y1)
+
+p0u = utm.point(x0, y0)
+p1u = utm.point(x1, y1)
+
+p0ul = utm.point(x0, y0).projection
+p1ul = utm.point(x1, y1).projection
+
+dist = Math.sqrt((p1ul.x - p0ul.x)**2 + (p1ul.y - p0ul.y)**2)
+
+puts "Mercator: #{p0m.distance(p1m)}"
+puts "Geographic: #{p0g.distance(p1g) * 111_300}"
+puts "Spherical: #{p0s.distance(p1s)}"
+puts "UTM: #{p0u.distance(p1u)}"
+puts "UTM Linear: #{dist}"